FE Power Forums
FE Power Forums => FE Technical Forum => Topic started by: Clark Coe on January 27, 2021, 04:20:17 PM
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What causes the very stock 390 in my ’68 Mustang to shake at 1000 rpm, 1500 rpm and most actively vibration at 2000 rpm? This condition is a shake/vibration (steering wheel quivers) and does not feel or sound like a misfire, exhaust tone is clean and even. Idles smooth at 550 rpm. At 3000-3500 rpm, no shake, no vibration.
To test the fan clutch and Ford seven blade fan for the source of this problem; I ran the engine with the alternator and power steering belts removed. The vibration remained.
This engine has always been a little rough. But after I installed a TKO 600 5-speed, 2000 rpm is the engine speed to cruise 65 mph on the highway. I am disappointed; I was expecting a butter smooth driving experience while cruising down the highway.
This engine is a budget rebuild, assembled by me in 1980. I started with a factory original 1968 X-Code (2V- 10.5 compression) 390 core I removed from a running ’68 GT Torino. I did not have the engine rotating components dynamically balanced…wish I had done this.
Here are some details:
Stock points distributor with new bushings. 16 degrees initial and 21 distributor degrees at 3300 rpm 18 inches of vacuum at idle. Stock Ford black with yellow ignition coil.
Pistons are 9.5 CR cast Badger P172 .030” over. 148 – 150 psi cranking pressure.
Stock rods were re-bushed and honed to fit.
Harmonic Balancer is original Ford. Timing marks are in the correct position. Outer ring has not slipped.
Do not know what cam I installed. May be the stock 390 X-Code cam from original engine. Mild profile.
Ford 600 CFM carburetor C8OF 9510-0 with a newer Holley kit.
Cylinders Heads stock C8AE-H – Rebuilt in 1980.
Streetmaster intake – not modified.
Stock GT exhaust manifolds and stock exhaust system.
McLeod steel flywheel 30 pound. New last year. Does not have the external (428) counter weight installed…I am smarter than that.
Pressure plate and clutch as supplied with TKO600 conversion from Modern Driveline.
What causes this vibration and what will be required to fix it? What next? Help Please? After 44+ years employment with one company and at age 68, I have finally retired and am looking forward to having time to be driving my Mustang....need to get it fixed.
Clark
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Does it vibrate while parked , driving , or both ? While it's driving ONLY would be a whole separate issue than if it did while idling also.
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It could be bad engine or transmission mounts. It could be the trans input shaft is not properly aligned to the crank. I know you say it's not a misfire, but it still could be if the carburetor is running lean or you have a wire crossfire.
Other things it could be are the substance of bad dreams. Bent rod, cracked crank...that kind of stuff.
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Where to start?...A vibration could be anything and volumes can be written on the subject. That said did it always vibrate from the time you built the engine? What flywheel? Vibration dampener? Does it vibrate out of gear, in gear, both? From my experience with a similar vibration problem on my F250 2wd, 390 +.030" mild hyd cam, single 600 Holley on a Streetmaster manifold it also had a shake at about the same rpm as yours. After changing the Street master for a iron "S" manifold, no other changes, even the same 600 carb the shake/shimmy was gone. All I could think of with this swap was the S/M had a idle/low speed fuel distribution problem. The "S" manifold is a dual plane, small runner high velocity manifold. I did not need to save the 50 or so pounds using an aluminum manifold on a 4800 lb truck. An added benefit of the S manifold was that my fuel mileage increased about 1.5-2 mpg, better low end torque even increased midrange torque somewhat. IMO a win/win situation all the way around plus it freed up a aluminum manifold for something more worthy and beneficial.
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This 2000 rpm vibration occurs when parked and also out on the highway.
It could be bad engine or transmission mounts. It could be the trans input shaft is not properly aligned to the crank. I know you say it's not a misfire, but it still could be if the carburetor is running lean or you have a wire crossfire.
Other things it could be are the substance of bad dreams. Bent rod, cracked crank...that kind of stuff.
Engine motor mounts are in excellent condition and the transmission mount is brand new with the TKO600 conversion.
Where to start?...A vibration could be anything and volumes can be written on the subject. That said did it always vibrate from the time you built the engine? What flywheel? Vibration dampener? Does it vibrate out of gear, in gear, both? From my experience with a similar vibration problem on my F250 2wd, 390 +.030" mild hyd cam, single 600 Holley on a Streetmaster manifold it also had a shake at about the same rpm as yours. After changing the Street master for a iron "S" manifold, no other changes, even the same 600 carb the shake/shimmy was gone. All I could think of with this swap was the S/M had a idle/low speed fuel distribution problem. The "S" manifold is a dual plane, small runner high velocity manifold. I did not need to save the 50 or so pounds using an aluminum manifold on a 4800 lb truck. An added benefit of the S manifold was that my fuel mileage increased about 1.5-2 mpg, better low end torque even increased midrange torque somewhat. IMO a win/win situation all the way around plus it freed up a aluminum manifold for something more worthy and beneficial.
Years ago I was fighting shrunken FelPro intake gaskets and closed off Holley idle circuit channels on my carburetor both at the same time. During this time, I had a Police Interceptor and a Sidewinder intakes on this motor. And now I am trying the Streetmaster. So I have lost my way in remembering exactly how it ran with the Police Interceptor. I will tell you that the Sidewinder did not seal well at the intake ports of my C8AE-H heads.
Has anyone else had vibration (fuel distribution) problem with Streetmaster intakes on low performance, low rpm motors? I really like weight savings of an aluminum FE intake. I have an aluminum Edelbrock water pump too.
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21deg of timing seems about 15deg retarded.
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21deg of timing seems about 15deg retarded.
37 degrees total at 3300 rpm. I have made a correction to my original post. 16 degrees initial and 21 degrees in the distributor.
Sorry for the confusion.
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So to back up a little . this thing didnt have this exact vibration before the trans swap ? If no then there you go . I take it the can be duplicated sitting in neutral ? Or is this only under load ? Saying it always ran a little rough . you mean idle ? Load ? No load ?
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Sounds like you have checked a lot of the typical sources. Can you get a view of the running flywheel and see if became bent somehow? How about the electrical system. Any loose power or ground cables/wires?
Was the TKO used to replace an Automatic? If so the vacuum system would have changed. Perhaps it effects the distributor advance.
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I've not been into the guts of a TKO but you can eliminate them buy disengaging the clutch. If it is still there the pressure plate or flywheel could be out of balance. If the pressure plate is off center you'll probably feel it easing off the clutch.
It could be a valve is not closing fast enough while running. Usually does not show up during cranking compression test. Pull your Shrader valve and do a running compression test. Your needle will be bouncing fast but will be readable. High side should be about 35psi. If a valve event is the cause that cylinder will have weak reading about 20 psi or less.
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Has the fan been checked? Stock, flex?
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Harmonic signature in tire? ( I build tires for a living ) It could be as simple as radial force variation in the tire, which is basically the roundness of a tire and the different stiffness the joints create.
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Clutch fan bad. Try to unhook the vacuum advance i have had them go bad and made the engine shake.
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I'd start with a compression check.
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He covered the last four responses in his original post. Or at least as of 4pm yesterday.
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Well he kind of dropped off but its not really that difficult. Is it load related or not . He said it was always rough . rough when ? With his current setup he may be seeing substantial load in that range which then dissipates as RPM increases . This can point at a few things real quick and then fans out to a broader range of items . Was it rough in this fashion before ? Did this roughness/vibration come with the trans swap ?
If he shoves the clutch in at that speed is the vibration still there ? Not hard to narrow down ..
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If he never had it balanced in the first place, isn't everything else sort of chasing your tail?
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I have seen some out of balance (new) clutches.
Easy enough to prove, just remove the clutch/pressure plate and start it up!
(Well not that easy, but it will prove it)
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I've not been into the guts of a TKO but you can eliminate them buy disengaging the clutch. If it is still there the pressure plate or flywheel could be out of balance. If the pressure plate is off center you'll probably feel it easing off the clutch.
It could be a valve is not closing fast enough while running. Usually does not show up during cranking compression test. Pull your Shrader valve and do a running compression test. Your needle will be bouncing fast but will be readable. High side should be about 35psi. If a valve event is the cause that cylinder will have weak reading about 20 psi or less.
The 2000 rpm shake is not related to load. The 2000 rpm shake occurs while sitting in the driveway (with the clutch engaged and not engaged) and when in motion on the highway. The 2000 rpm shake is the strongest and most annoying…that is the one I need to fix.
The 2000 rpm shake occurred with the stock Ford flywheel, Ford three finger pressure plate and Ford clutch that was balanced and installed in 1980. Last year, a new McLeod steel flywheel and a new Kevlar/Organic clutch disc and diaphragm plate were installed with the new TKO600 5-speed conversion. This tells me the vibration problem is not in the drive train and must be in the engine.
The Streetmaster intake has been on this engine for twelve years. But, I have not driven my Mustang more that a couple of hundred miles in that time. I am getting old and it is time to get my car out on the road and enjoy it. It is time to finally get this 2000 rpm vibration problem figured out....I thought a new flywheel and clutch assembly would do the trick. I was wrong.
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Pull out both air/idle screws and blow out the passages with high pressure air. Point is to unblock any crap from the emulsion tubes. Fast, easy to do and may work to your advantage.
Next, swap on a known good carb and run it. Harder to do but it could help isolate on issue: is it carb related?
Very hard to do and a total PITA. Pull the tranny, remove the throwout bearing and arm, block up the engine at the pan and fire her up. If it still shakes, then yank the bell, remove the clutch and disc, refire it and see if your shake disappeared.
Story time! My late, great Uncle Bill bought a brand new black1957 Ford and love it. But, it had from Day 1 an odd vibration at various engine speeds. The dealer took the car in a few times but the local mechanics could not source the issue. Bill, being a stickler and standing by his rights (new car and all) pursued Ford with letters, etc. to fix the engine or give him a new one. Ford's Dearborn office did send a factory repr. as the dealer gave up. Bill took the car in on the appointed day and the factory guy pulled the engine, totally disassembled it and went to work. IIRC, it was two days later the call came in to Bill to visit the dealership. The rep, showed Bill all 8 connecting rods, pointing out the machined balance pads on each one's big end. One rod showed zero machining on its big end! He had taken all 8 to a local machine shop and had each one weighed. That one rod was way out of balance compared to the other 7. A touch of machining to match the others, a reassembly and the engine engine finally engine ran smoothly.
Hope yours hasn't the same issue!
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I've not been into the guts of a TKO but you can eliminate them buy disengaging the clutch. If it is still there the pressure plate or flywheel could be out of balance. If the pressure plate is off center you'll probably feel it easing off the clutch.
It could be a valve is not closing fast enough while running. Usually does not show up during cranking compression test. Pull your Shrader valve and do a running compression test. Your needle will be bouncing fast but will be readable. High side should be about 35psi. If a valve event is the cause that cylinder will have weak reading about 20 psi or less.
The 2000 rpm shake is not related to load. The 2000 rpm shake occurs while sitting in the driveway (with the clutch engaged and not engaged) and when in motion on the highway. The 2000 rpm shake is the strongest and most annoying…that is the one I need to fix.
The 2000 rpm shake occurred with the stock Ford flywheel, Ford three finger pressure plate and Ford clutch that was balanced and installed in 1980. Last year, a new McLeod steel flywheel and a new Kevlar/Organic clutch disc and diaphragm plate were installed with the new TKO600 5-speed conversion. This tells me the vibration problem is not in the drive train and must be in the engine.
The Streetmaster intake has been on this engine for twelve years. But, I have not driven my Mustang more that a couple of hundred miles in that time. I am getting old and it is time to get my car out on the road and enjoy it. It is time to finally get this 2000 rpm vibration problem figured out....I thought a new flywheel and clutch assembly would do the trick. I was wrong.
Ok, move on to my next paragraph.
EDIT: Don't let it overwhelm you. We all get so frustrated we don't always see everything.
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Check your balancer to see if it's cocked a tad due to dried-out elastomer that bonds the inner hub to the outer ring. Old balancers can in fact cause shakes if they are not running true.
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Very hard to do and a total PITA. Pull the tranny, remove the throwout bearing and arm, block up the engine at the pan and fire her up. If it still shakes, then yank the bell, remove the clutch and disc, refire it and see if your shake disappeared.
I bought a 67 Shelby in 1978 and it had the shakes the day I brought it home. It was a 4spd car and had been modified with a 427 short block. I pulled the pressure plate and right away I could see it was the problem. It had loose and misadjusted parts and wasn't even parallel to the flywheel.
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Check your balancer to see if it's cocked a tad due to dried-out elastomer that bonds the inner hub to the outer ring. Old balancers can in fact cause shakes if they are not running true.
Today I removed the three groove crank pulley to get a better look at the original, 52 year old balancer.
Using a dial indicator, I found the outer ring has .023" run-out, measured on front surface. The rubber strip between the two inner and outer rings is old and dry. The .023" variance corresponds to the two pooched out, cracked areas that are 180 degrees apart, see pictures below. This quite likely is the source of the 1000/1500/2000 vibration.
What to you guys think?
How long should a balancer last? ::) I would have looked at this sooner, but using a piston stop I determined that the outer ring had not slipped and the timing pointer indexed on TDC....on that observation, I thought the balancer was okay. I have never heard of the outer ring tipping horizonally
(https://i.postimg.cc/13LjNMqp/1969-Indicator-Dial.jpg) (https://postimages.org/)
(https://i.postimg.cc/cC9D1cWt/20210129-144906.jpg) (https://postimages.org/)
(https://i.postimg.cc/KzLFMRjY/1968-Balancer-1.jpg) (https://postimages.org/)
(https://i.postimg.cc/WpktG1Cg/1968-390-2021.jpg) (https://postimages.org/)
(https://i.postimg.cc/R0gvBj8M/1968-Clark-Mustang.jpg) (https://postimages.org/)
What brand do I look for in a quality OEM replacement? This is a street motor, but I still want a good one with precision timing marks.
Thanks for all of the replies and suggestions.....Clark
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Clark that balancer is junk, it is in the very least moving but it almost looks like it’s wet all the way around. Even if it’s not the source of your shake, which probably is, just swap it out before it comes off and breaks something
New replacements are cheap, Pioneer, and others. There is a decent company in Kansas I’ll see if I can find their card and post it here tomorrow
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Beautiful car and yeah , ditch that balancer either way... I think you have narrowed this down pretty far with that last long post. Its going to be that balancer or something internal. Thats my two cents...Things like bad carbs or ignition issues are always exacerbated by load and usually get worse with time . Since your issue seems to have hung on and been consistent it seems like a hard balance issue. The nicer the car the more obvious small issues are and it looks like you have a really nice car there.
An old beat up car with a bunch of other issues covers up the small issues....
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Clark that balancer is junk, it is in the very least moving but it almost looks like it’s wet all the way around. Even if it’s not the source of your shake, which probably is, just swap it out before it comes off and breaks something
New replacements are cheap, Pioneer, and others. There is a decent company in Kansas I’ll see if I can find their card and post it here tomorrow
Thanks Ross, I will be looking forward for the info from the Kansas source. I have also found a Pioneer OEM balancer PIO-872056 for $232.99 at Summit Racing.
Beautiful car and yeah , ditch that balancer either way... I think you have narrowed this down pretty far with that last long post. Its going to be that balancer or something internal. Thats my two cents...Things like bad carbs or ignition issues are always exacerbated by load and usually get worse with time . Since your issue seems to have hung on and been consistent it seems like a hard balance issue. The nicer the car the more obvious small issues are and it looks like you have a really nice car there.
An old beat up car with a bunch of other issues covers up the small issues....
Blueoval77, thanks for the compliment on my fastback. Yes, that car is extra special to me. Have owned it for 51 years, since 1970. I am the second owner. Currently has 69K miles, I would guess that half of those miles are on Nebraska gravel roads. Original paint, but the closer you get, the more worn out it is. I did a lot of back roads cruising in my long ago youth. The eight track player has been removed but the tunes still remain in my memory.
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I just got a power bond from Brent, looks like a nice piece, didn’t break the bank.
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Ditto on the one pictured above . Blykins..........
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Clark, my mistake, sold in KS, made in Mexico. I have used a few of these and they are nice. I don't pick them for strokers, only because most of them live up near 6000, but wouldn't think twice on a street GT.
Regardless, there are a ton of quality big balancers out there for a stock-ish 390 that work real well, I wouldn't spend more than 100 unless you are planning a high rpm engine or stroker later
https://aacincdirect-com.3dcartstores.com/1968--1976-Ford-360-390-428-Damper_p_61.html
The ones I had all came out right for TDC, and have graduated timing marks and were balanced correctly when stuck on the crank during balance
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I had a vibration/drone in my 428CJ for years. I had the stock pistons replaced with forged TRW's on the rebuild. The machine shop that did the work said I didn't need it balanced although I wanted it done. The machinist was an old bastard set in his ways and no one knew anything but him. Well the engine shook but I never drove it much and it used oil from day one. It finally shook the
damper loose and just about screwed up the key way. Took one of my spare CJ blocks up to Barry and had him put in a new Scat stroker rotating assembly. That was the best money ever spent
on that car. Smooth as silk and never used oil, ever. The number matching motor is now on a stand out of harms way. The stroker is just a joy to drive. The moral of this story is always have
them balanced. That's one thing you can rule out when chasing problems. Good machinists/ engine builders like we have on this forum are a huge advantage. Steve
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Clark, my mistake, sold in KS, made in Mexico. I have used a few of these and they are nice. I don't pick them for strokers, only because most of them live up near 6000, but wouldn't think twice on a street GT.
Regardless, there are a ton of quality big balancers out there for a stock-ish 390 that work real well, I wouldn't spend more than 100 unless you are planning a high rpm engine or stroker later
https://aacincdirect-com.3dcartstores.com/1968--1976-Ford-360-390-428-Damper_p_61.html
The ones I had all came out right for TDC, and have graduated timing marks and were balanced correctly when stuck on the crank during balance
Ross, thanks for the referral. To check on availability of a 390 balancer. I called Advanced Automotive Componets, Saturday afternoon and someone actually answered the phone and confirmed in-stock availability....I was impressed. Got one ordered on their web site.
I had a vibration/drone in my 428CJ for years. I had the stock pistons replaced with forged TRW's on the rebuild. The machine shop that did the work said I didn't need it balanced although I wanted it done. The machinist was an old bastard set in his ways and no one knew anything but him. Well the engine shook but I never drove it much and it used oil from day one. It finally shook the
damper loose and just about screwed up the key way. Took one of my spare CJ blocks up to Barry and had him put in a new Scat stroker rotating assembly. That was the best money ever spent
on that car. Smooth as silk and never used oil, ever. The number matching motor is now on a stand out of harms way. The stroker is just a joy to drive. The moral of this story is always have
them balanced. That's one thing you can rule out when chasing problems. Good machinists/ engine builders like we have on this forum are a huge advantage. Steve
Hello SReist. I do wish I had the money in 1980 to balance this engine. I am really hoping a new balancer fix in my engines 2000 rpm shake.
I do plan to follow your path to a 428 stroker. I have three 428 industrial motors in storage that need to be disassembled and inspected for a usable block. There is 462 stroker in my future.
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No joy! Installed new balancer, but the 390 motor in my Mustang still shakes at 2000-2400 rpm! >:(
Last night I installed a new stock balancer from Advanced Automotive Components in McPherson, Kansas. Then today, with the Nebraska outside temperature at 8 degrees Fahrenheit, I opened the garage door and started and warmed up the motor at idle, only to confirm the 2000-2400 rpm vibration remains the same. Engine continues to be much smoother at 3000-3500 rpm.
Next, I plugged all vacuum hoses (power brake booster, PVC valve and tilt wheel vacuum storage canister) attached to the Streetmaster intake. Disappointingly, the 2000 rpm shake remained. Vacuum at 550 rpm idle remains a very steady 17 inches.
The new balancer came with deep stamped timing marks to 30 degrees. Top Dead Center precisely aligned with the timing pointer. For $69.50, this was a well-made balancer. Like Ross said the original 53 year old balancer was junk, I had to remove the crank pulley to be able to see the rotten rubber ring. It was bomb just ready to destroy the radiator, fan and pulleys.
(https://i.postimg.cc/K8Lq72HG/20210205-193744.jpg) (https://postimages.org/)
I wish I had spent the extra dough to have this engine balanced when I built it in 1980. I was short of funds at that time to spend more than I did. Given that it was a 9.5 compression, mild cam street build, not balancing seemed like a reasonable gamble…guess not. Do not want to disassemble this engine, has even compression, does not smoke or does leak oil.
Is there anything more to check?
Thanks for everyone’s input.
Clark
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I would remove the clutch etc and run it again. I know what a pain it is to do especially when it is 9 degrees outside but I suspect you have an unbalanced clutch assembly.
With the tranny pulled back and no clutch assembly on the engine then it is in the engine.
These problems are a real pain to figure out.
Greg
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Clark, I am buried this week but may have some time next Sunday if you want another set of eyes on it.
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Just to rule it out, unplug the vacuum advance and see if that makes any difference. I think you're looking at a mechanical imbalance but you for sure want to make sure you've snatched the low hanging fruit.
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I would remove the clutch etc and run it again. I know what a pain it is to do especially when it is 9 degrees outside but I suspect you have an unbalanced clutch assembly.
With the tranny pulled back and no clutch assembly on the engine then it is in the engine.
These problems are a real pain to figure out.
Greg
Greg, thank you for the suggestion. I have had two different, complete flywheel/pressure plate/clutch disc assemblies in my Mustang. The all Ford component flywheel assembly installed in 1980 was dynamically balanced by a reputable shop and the new, last year McLeod flywheel and 26 spline diaphragm plate/clutch assembly from Modern Driveline. This vibration has deviled me with both assemblies. I suspect either hard parts imbalance in the engine or a fuel distribution/calibration problem with the carburetor.
Just to rule it out, unplug the vacuum advance and see if that makes any difference. I think you're looking at a mechanical imbalance but you for sure want to make sure you've snatched the low hanging fruit.
Gerry, I did not mention it, but I did try disconnecting the ported vacuum advance line and it made no difference. I have been thinking about pulling all of the plugs and to read on their condition and color.
Clark, I am buried this week but may have some time next Sunday if you want another set of eyes on it.
Ross, that would be great if you could spare some time. My Mustang is in an insulated and heated garage. It is a balmy 45-50 degrees F out there...lots better than 48 years ago when I wrenched on this car on my father's farm, in a converted chicken shed with a Knipco kerosene heater. That garage had holes in the foundation that a possum could climb through. It was drafty enough that there was no chance to be overcome by combustion flumes from the kerosene heater.
Thanks all. Clark
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Beg, borrow or steal an known good carb just for giggles?
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Clark,
I got your message and will shoot you an email. Good advice here on the forum. I would start this week by looking close at the distributor cap and rotor for tracking, potentially the coil for arcing to the intake, maybe check resistance of the plug wires and separate them, ugly if required, to ensure no cross fire
I do have both an operable 1850 and 3310 if it comes to that, but the vibration at that high of an RPM seems more of a crossfire, scatter, or dropped spark to me, at least without hearing it
I would also be very surprised if it was a balance issue, assuming it's a 390 crank. It takes a bunch of weight to make them shake when everything is zero from the start, unless you have a broken skirt, etc. Although, if nothing else found, you could check crank end play in the car to see if at an early time in the rebuild, you took out a thrust bearing. Not generally a shake, but if things can move around, sometimes they can do funny things
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Any unbalance would get worse as the rpm increase, and would not go away at a high rpm and come back in. Balance does not come and go in rpm changes, it magnifies itself with rpm. Joe-JDC
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Have you checked for a sacked out mount, or a line or hose or anything fouling the body?
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I know its a 390 but if you still have the 428 weight and can bolt it on not sure if can get to it with bell on. See if shakes more or less it will cost nothing just to see.
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Just for reference I swapped a 300 inline 6 for a 351 W many many years ago and being young used the 6 banger flywheel and clutch and the whole thing. What could go wrong ????
It has a vibration exactly like he is talking about here and yes Joe , I know it makes no sense but it did go away with more rpm.... It was an old 4x4 truck and I was in my 20s so how much it went away is up for grabs but it certainly lessened to the point that the guy that owned the truck didnt want to spend the money on the right wheel and swap it.
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Did you check your pilot bushing/bearing? Worn or missing needles can let the trans input shaft wobble/run out of round and chatter/or cause imbalance. Joe-JDC
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I didn't notice it, but have you put an dial indicator on the flywheel/crankshaft assy?
(I.E. is it concentric and square? I have had one engine where the crankshaft flange was not true. The man that balanced the rotating assy caught it. I remachined the flange in the lathe, it was out about .005" which is magnified at the flywheel rim!)
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last easy things to try possible carbon tracks in dist cap often does wierd things try new one and different carb possible metering change / valve lift bad lobe/spring also can do strange things -good luck
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I didn't notice it, but have you put an dial indicator on the flywheel/crankshaft assy?
(I.E. is it concentric and square? I have had one engine where the crankshaft flange was not true. The man that balanced the rotating assy caught it. I remachined the flange in the lathe, it was out about .005" which is magnified at the flywheel rim!)
Using a dial indicator, I measured .008” of Flywheel Clutch Face Runout. This was measured at the very outside diameter of the McLeod flywheel. While .008” is not a great value, it is inside of the Ford specification of .010” maximum.
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Last November, I had total knee joint replacement on my right leg. I am still recovering from that surgery (also recovering from twice-a-week, extensive, ongoing physical therapy). As such, I can work in the garage until the swelling and pain forces me into the house for an ice pack. But I continue to work on my 2000 rpm vibration.
So far, I have successfully identified the following items are NOT causing my 2000 rpm vibration.
Not the spark plugs. Plugs are clean and dry. One side of porcelain is white (front row), the other is dark tan (back row). Gasoline is 91 octane unleaded premium. Checked the gaps to .035” and reinstalled plugs….be sure to recheck the gaps if you drop them on the concrete floor.:( Any problems here? Some dark speckles?
(https://i.postimg.cc/kXtKNyMN/Spark-Plugs.jpg) (https://postimages.org/)
Not the plug wires. Replaced wires with new, premium NAPA – Belden EDGE BEL 7000142. The new NAPA 7mm wires all measured very low resistance, 4900 to 5500 ohms, I was impressed. The old, previous Motorcraft wires measured 15,000 ohms (plus/minus).
Not the rotor, but I replaced it anyway with a NAPA – Echlin ECH FA 157. Here is the original.
(https://i.postimg.cc/gj1RFxs6/Rotor-USA.jpg) (https://postimages.org/)
Not the Motorcraft distributor cap, but replaced it with a NAPA – Echlin ECH FA79 (brass terminals). Here is the original, clean as a whistle.
(https://i.postimg.cc/Jn4jbVtt/Motorcraft-Cap.jpg) (https://postimages.org/)
Not the old, factory coil. My Ford coil tested good to Ford specs, Primary = 1.5 ohms. Secondary = 7500 ohms. Not sure if orange color arc is good, but it would jump +3/8” inch. The spark color across .035” gap on an Autolite plug was a satisfactory blue/orange color.
(https://i.postimg.cc/QCK9bXDN/Spark-1.jpg) (https://postimages.org/)
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Yesterday afternoon, I installed a Pertronix II ignition module and the supporting Flame-Thrower II ignition coil. This did not make the 2000 rpm shake disappear, but the engine seems to start a little easier and settle to an 700 rpm idle sooner. Measured the voltage at the + terminal on the coil and got 11.98 VOLTS. Guess the resistor wire does not work, I was expecting 9 volts.
(https://i.postimg.cc/d08vd60x/pertonix-ignitor-II.jpg) (https://postimages.org/)
What to check next? At 2000 rpm, the ignition advance is 27 degrees, does that seem correct? At 2000 rpm, fuel is dribbling out of the primary boosters, looks kind of sloppy as it piddles out. Should the carburetor be metering the fuel from the boosters at this time?
The primary jets are #66. Would trying #68 jets be the correct direction?…richens the mixture a little bit for the single plane Streetmaster intake?
Thanks for everyone’s input and suggestions. Remember, it’s Valentine’s Day….hug your honey! :-*
Clark
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Speckling on the plugs is usually a sign of detonation. But it depends upon what the specks are. Sometimes, it's just carbon spotting. Sometimes it's aluminum from the pistons.
If you are sitting still and the engine is turning a stable 2,000 rpm, no fuel should be coming from the boosters. If you wang the throttle and the carb is right, you can usually get booster flow. If you open the throttle by hand and the engine is running at 2k RPM, the throttle isn't open very far and you are operating on the idle and intermediate circuit. Fuel coming out of the boosters could mean your fuel level is too high or you have a very tiny air bleed in the main metering. Booster fuel comes from the main jets and the power valve. But check your fuel level first.
What size is your carb? A 66 jet would be fine for a 600CFM carb. That's too small for something like a 750CFM. And a single plane always takes more jet than out of the box. If out of the box was a 66 jet, then you need around six sizes larger, or around a 72. You might have a lean surge going on there.
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Bah that fuel "Dribbling" out can cause a myriad of things depending on how much there is . Ive had a few act common from that over the years....Didnt someone mention before about swapping a known good carb just to see if there was any change ?
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Bah that fuel "Dribbling" out can cause a myriad of things depending on how much there is . Ive had a few act common from that over the years....Didnt someone mention before about swapping a known good carb just to see if there was any change ?
Yes, I did. Beg, borrow or steal a known good carb.....................
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You asked what to check next, did you check the running compression that was suggested earlier? Look in your compression gauge instructions.
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Sounds unrelated but for whatever reason the two barrel Holleys on the small Ministock engines I have fooled with over the years were prone to that dribbling deal at part throttle and I cant remember now what I did to stop it but it was very very annoying...
Maybe if I bang my head against the wall the answer will fall out.... There was a logical answer for it...
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Depending on which TV station we listen too, tonight's low temperature forecast for eastern Nebraska is -27F to -30F. High temperature forecast for tomorrow is ZERO. Because of the cold weather today, the Omaha area electrical power company was doing controlled brownouts to regulate power consumption. Didn't happen to my house, at least not yet.
So until the outside temperature increases by a bunch, I am keeping the garage door down and not completing any more running tests on my 390. Not messing with anything related to gasoline in the garage. Later in the week, I am going to check the fuel levels in the carburetor bowls and clean/blow out the air bleeds. But not inside my heated/attached garage.
Thank you to everyone for you suggestions and insights.
Clark
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Clark, sorry I couldn't get to you. Been swamped and cold weather slowed me down as we look for homes outside of town.
A couple of things.
1 - Compression check is smart, doesn't hurt to know what you are seeing even if it is good
2 - Do you have any valve train noise when the shake starts?
3 - Have you looked at the advance curve as it comes in? Might be hard to do with one person, but it should be consistent with RPM, if it jumps, maybe the advance weights are sticking and its retarded then releases. You could add 10 degrees initial after it starts (can't really drive it that way, but if it changes it tells you something. No load it'll be fine)
4 - Could you record a movie of the exhaust when it's in the shake?
5 - When it is hot, and the choke is open, if you cup your hands over the carb, does it rev up slightly before it chokes? (Don't use the choke plate, use your hands, watch your jacket and hoodie for the fan etc)
After that, likely smart to bolt on either a 600 I have or a 3310 and see what it does. I am working out my schedule, sorry I vanished, we can likely get together soon if you don't figure it out
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Was the Torino that you pulled the engine from crashed? If not, did you drive it b4 pulling it, noticing any vibration? You had this vibration from day one of the rebuild? I had a 289 that I went through with this. Pulled it from a crashed Mustang that was hit hard and low in the front. I just put up with it until one day a rod nut vibrated loose and it puked it's cookies. I too had changed transmission, clutch & flywheel to no avail.
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unlead gas hard to read plugs- yours may look lean check w/known carb/fuel psi-be positive !! timing-spark plug heat range or new set -if available o2 sensor - total fresh fuel - I like ngk plugs-bp fuel after all the items have checked out you may need to get inside engine vs chasing all things you have worked at esp. if internal before hard damage happens-worked at ford dealer early 70s seen factory .030 piston on one cyl!! balance issue!! if internal and done you can enjoy rather than long term issue good luck
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.030 piston on one cyl!! balance issue!!
Ford over size replacement pistons are the same weight as standard. OEM warranty repairs allowed individual cylinder boring and piston replacements.
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A couple of things.
1 - Compression check is smart, doesn't hurt to know what you are seeing even if it is good
2 - Do you have any valve train noise when the shake starts?
3 - Have you looked at the advance curve as it comes in? Might be hard to do with one person, but it should be consistent with RPM, if it jumps, maybe the advance weights are sticking and its retarded then releases. You could add 10 degrees initial after it starts (can't really drive it that way, but if it changes it tells you something. No load it'll be fine)
4 - Could you record a movie of the exhaust when it's in the shake?
5 - When it is hot, and the choke is open, if you cup your hands over the carb, does it rev up slightly before it chokes? (Don't use the choke plate, use your hands, watch your jacket and hoodie for the fan etc)
After that, likely smart to bolt on either a 600 I have or a 3310 and see what it does. I am working out my schedule, sorry I vanished, we can likely get together soon if you don't figure it out
Ross, here are some answers:
1.) I have completed a dynamic, running compression test and here are the results. Static compression looks good for 9.5 CR pistons. All of the 3000 snap readings are too high, suggesting some restriction in the exhaust system. What next? My Mustang has a complete, stock exhaust system, complete with twin exhaust resonators and crossover muffler behind the rear axle. Remove the muffler?
(This running test consumed three Schrader valves. The valves have a limit of how much pounding they will tolerate. Tried removing the Schrader valve, but the gauge was too difficult to read.)
(https://i.postimg.cc/BbpgQYck/compression-test-March-2021.jpg) (https://postimages.org/)
2.) Valve train makes no odd noises. Have Pumpbuilder rocker spacers and end stands. Have adjustable, factory rocker arms.
3.) Mechanical advance starts to move at 1750 rpm, then moves smoothly for 21 degrees to be fully advanced at 3000 rpm. I adjusted the initial to 24 degrees and that did not make a difference in the vibration.
4.) I do not know how to post videos of my exhaust? Will Postimages.com host videos?
5.) Clamping my hand on the carb inlet chokes out the engine without any rise in speed....no vacuum leaks.
Was the Torino that you pulled the engine from crashed? If not, did you drive it b4 pulling it, noticing any vibration? You had this vibration from day one of the rebuild? I had a 289 that I went through with this. Pulled it from a crashed Mustang that was hit hard and low in the front. I just put up with it until one day a rod nut vibrated loose and it puked it's cookies. I too had changed transmission, clutch & flywheel to no avail.
Shady: In 1980, I bought the 1968 GT Torino for $50, drove it home and removed the motor. The Torino was not wrecked and I do not recall any clues of substantial body or frame damage. It was a very odd Jade Green Torino, GT option with 2V-premium gas 390, three on the tree, AC, bench seat and a open rear differential.
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Not sure if this has been mentioned hopefully you have checked the firing order. Have you tried pulling one wire off at a time to see if they make any difference in the idle.
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Clark , if you stand over the thing running with a light pointed down into the choke horn . If you slowly raise the RPM does the roughness start with the "Dribble" from the carb ?
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Not sure if this has been mentioned hopefully you have checked the firing order. Have you tried pulling one wire off at a time to see if they make any difference in the idle.
sixty9cobra: Checked that, all okay. And rechecked it again when I installed new NAPA spark plug wires two weeks ago.
Clark , if you stand over the thing running with a light pointed down into the choke horn . If you slowly raise the RPM does the roughness start with the "Dribble" from the carb ?
Blueoval77: The vibration sort of begins before the "dribble", maybe 1950 rpm. When the dribble at the booster appears, the engine speed surges 200-250 rpm to 2200 - 2250 rpm. The carburetor's transition from idle to the booster circuit seems abrupt, not smooth.
I have battled with this '68 390GT C8OF-D carburetor before.
http://fepower.net/simplemachinesforum/index.php?topic=3042.0;all
The primary #211 butterflies have small factory holes and the carb has two, separate idle adjustments for each primary plate. See old thread. I finally got the engine to idle very well, but there still is some idle/primary transfer tuning required that is not yet in my skill set. The idle screws in the metering block are 1.5 turns out.
This vibration is more pronounced in the interior of the car, like the vibration becomes an audible sound. This vibration/sound may have always been there and now I am more fussy about it and really noticed it.
As I am thinking about this, my new reduced height TKO 600 conversion is still very tightly positioned up near the transmission tunnel. It is possible that the transmission is just touching the body somewhere. I have already looked at this but could not see or feel any transmission/body interference. I would have to remove the transmission to look for any witness marks. Have to fix the vibration first.
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Well along those lines . I had a 2017 Subaru that I got for my niece and put back together from the Salvage auction . This thing had pretty light damage in the front end mostly involving strut , control arm , etc....Once it was all back together and running it had the same thing you describe . You could feel and maybe more hear something was off. Everyone else that got in the car said Oh its fine !!! And it nagged at me....At a certain RPM it would do this thing . Not a shake so much as a sound and feeling that something was off... After going over and over and over this thing on the lift about a million times I finally found that in the impact the trans mount had a sort of limiter inside of the rubber isolator that got bent and it was touching metal. This was no more than maybe a .250 rod inside of there and it annoyed me to no end...I pried it back straight and that was that... So it doesnt take much to get what you are describing....
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I did a lot of NVH work at Ford. ANY metal-metal contact with a powertrain component will cause booming in the cabin and drive you nuts. That TKO conversion has me wondering if you've got a clearance issue in the tunnel. Maybe the trans mount is twisted or hard against a stop?
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Clark,
Sorry I haven't been around to help out, more excuses, but have a bit more things going on than I generally do, or intend to in the future.
However, at this point. Potential contact points for the TKO
1 - Directly under the radio - it gets tight at and around the vent valve
2 - Right at the seat cross member on the bottom of the floor
3 - At the shift lever depending how you trimmed
If you dropped the tail of the tranny to avoid cutting or hammering too much, I would look at the angle of your Z-bar and see if it is binding slightly at a different agnle or pushed too tightly together causing metal to metal.
Then the normal exhaust chasing for hangers or pipes being tight, etc
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I did a lot of NVH work at Ford. ANY metal-metal contact with a powertrain component will cause booming in the cabin and drive you nuts. That TKO conversion has me wondering if you've got a clearance issue in the tunnel. Maybe the trans mount is twisted or hard against a stop?
Bill, I think I am on to something concerning the annoying drumming sound in my Mustang cabin. Thanks for encouraging me to take a second look. When I completed the TKO conversion, I was careful with the clearance and fit in the tunnel area. Even with the optional cut-down case, a few well-placed hammer blows were required. Did not look that close at the trans mount area.
Today I pulled out a untried, Holley 4150 1850-2 from under the bench. It already had a fresh renew kit in it, but I have never run it on any engine. Took a couple hours to work out some bugs and install it on my 390. Anyway, the vibration and cabin sound remained at 1950 rpm - 2200 rpm range. However, this carburetor did not dribble as much at 2000 rpm.
Turned the idle up to 2000 rpm, slid under the car and held my hands on the underside of the tunnel. It was really vibrating.
While I was lying on concrete, on my back and trying not to burn myself on the exhaust, inspected the TKO transmission mount. Thought this looked suspicious
(https://i.postimg.cc/gcH0YNQr/TKO-Mount-Fit.jpg) (https://postimages.org/)
Took a break to allow the exhaust to cool, moved the Mustang to the middle of the garage and put it up on four jack stands. Removed the transmission mount and found a contact mark where the transmission case and the mount were touching. Those are not cracks in the transmission case, just casting parting lines and a scratch in the aluminum.
(https://i.postimg.cc/26p55JCL/Mount-with-mark.jpg) (https://postimages.org/)
(https://i.postimg.cc/Zn4K8dBT/TKO-rub-spot.jpg) (https://postimages.org/)
By now, it was time to grill some pork tenderloins, enjoy a Shiner beer and have some supper with my wife.
Tomorrow, I will get out my trusty grinder and create some clearance between the trans case and the mount.
Once again, I really appreciate everyone's input.
Clark
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... After going over and over and over this thing on the lift about a million times I finally found that in the impact the trans mount had a sort of limiter inside of the rubber isolator that got bent and it was touching metal.
Clark-
It was Blueoval77's Subaru story that really got me thinking about your issue. I can't take much credit, but I was reminded of a couple of Mustangs I've worked on over the years with degraded transmission mounts. It's amazing what a tiny contact patch can do!
Make sure you give yourself a good quarter inch if possible. Stuff moves around a lot in that area. Hope you enjoyed the nice steaks and the Shiner!
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Good detective work Clark, that will certainly make a noise....give it as much room as you are comfortable. Although it shouldn't move much fore/aft, certainly can see it does some
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I'd take it all off the steel crossmember. Good catch and I'll venture that was the cause. Know you will fill us all in after your grinding session and a test drive.
Great example of how Jay's Forum has allowed a ton of replies, all in the spirit of helping out another member, eh?
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Found my vibration and the source of the 2000 rpm cabin noise! :)
This is from an assessment by running the Mustang in the garage. There is too much embedded salt dust in Nebraska's roadways and a few snow piles still melting into the street, so I did not take it out for a drive.
After removing the interference between the transmission case and cross-member, the maddening vibration/sound is gone. :D Plus, the Mustang now has an updated ignition system. Another plus is the faint gear whirling noise at idle with the clutch out, that could be heard in the cabin is gone.
(https://i.postimg.cc/kXP6v6Q0/20210307-173122.jpg) (https://postimages.org/)
You could feel and maybe more hear something was off. And it nagged at me....At a certain RPM it would do this thing . Not a shake so much as a sound and feeling that something was off... After going over and over and over this thing on the lift about a million times I finally found that in the impact the trans mount had a sort of limiter inside of the rubber isolator that got bent and it was touching metal. So it doesnt take much to get what you are describing....
Blueoval77, Thank you for sharing your Subura story. That was great motivation for me to keep looking.
This clearance crack required alot of time with a 7" disc grinder. Had to weld the opposite side of the bracket because this clearance removed all of the origin welds. Will need to repaint it.
(https://i.postimg.cc/J43y6rKG/20210308-183209.jpg) (https://postimages.org/)
Great example of how Jay's Forum has allowed a ton of replies, all in the spirit of helping out another member, eh?
machoneman: Isn't that the truth! I am so appreciative of everyone here on Jay's forum that commented and contributed to finding a remedy to this vibration.
Thank you all.
Clark
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Nice!
I love it when a plan comes together :D
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Great news and good that it was not something costly.
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Whats the odds of that one being the trans mount too in the end.... Thats crazy and awesome at the same time..... Man Im glad that worked out. I indeed understand how annoying of a thing that is and mine was with a 4 banger ......
It will all feel three times as good after being able to make a run down the road..
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Yay !!
Ricky.