FE Power Forums
FE Power Forums => Non-FE Discussion Forum => Topic started by: 615STEELE on March 23, 2018, 01:13:08 PM
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Been lurking for a while, first time to post. Just wondering where the bottle neck is on my engine, and what would make the most improvement. engine info: 428 +.030, 268 comp cam, edelbrock heads, flat top speed-pro pistons, .008 in hole, edelbrock intake, Quick fuel 780 vs, CJ exhaust manifolds with 2.5 inch exhaust. Vacuum runs 13 in at idle, which seems low for power brakes, never have been able to raise it , changed intake from PI to edelbrock no change in vacuum. Didn't degree cam. Street car only no stats other than seat of pants. Was a GTA, installed a sb toploader with truck bell last year.
1966 fb mustang, 351w
1966 f100, 351w
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How many miles on the engine?
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Need more info, WHICH Edelbrock intake? Several models to chose from. What gear ratio, close or wide ratio toploader? What does the car weigh? If you have taken the can to the dragstrip, what did it run, & what are your expectations? If not raced, what are you using to determine that there is a bottleneck"? What ignition and timing spec? I agree, 13 in at idle seems pretty low for a Comp 268H, my 69 Mach 1 428CJ had that cam and stock CJ exhaust manifolds, and had 17-18 in.
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Engine has around 1000 miles,3:50 rear , rpm intake, It runs good. but rough idle. no track time. Any take off above idle will break the tires loose. Just am wondering if my combo would support a cam change and add to performance. I am guessing around 3400#, aluminum waterpump heads and intake.
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A fresh engine will have low vacuum until it is broken in. 1K miles is not enough, get some miles [2500-3K] on the engine and recheck, it should come up to 16-17" which is enough to operate the power brake booster. Changing intakes made no difference, it won't unless it was leaking. You say there is a 'bottleneck'... In power/torque? If you can "break the tires loose" at anything above an idle what exactly are you looking for?
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... You say there is a 'bottleneck'... In power/torque? If you can "break the tires loose" at anything above an idle what exactly are you looking for?
I'm gonna go out on a limb here and guess Mr. Steele discovered that his engine doesn't wind up as high as he thought it might. The 268 is a good torquey stick, but it really doesn't pull any higher than a stock CJ grind. I had one in an almost identical engine/exhaust car, and it was finished by 5500 or so. The cam I pulled out of there was some badass 580/590 Crane Compucam solid with shell lifters. It was good for 6000 or more. Ironically, the Crane worked the power brake booster just as well as the 268.
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My experiance with the 268H was pretty similar to FElonys, pulled well to 5500RPM, or maybe a touch less, but frankly, I kind of like to keep the RPMs kinda low on a FE anyhow.Accentuate the natural torque, and keep the innards INSIDE the oil pan.High RPMs come at a cost, both financialy, and mechanically, and I can`t say I have been disppointed with the results, on the street, or the track. If you can already light up the tires so easily, not sure what you are looking for, but if it was me, the first thing I would do is ditch the iron exhaust manifolds in favor of headers.
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Looks like headers will be my next project. Hope someone makes a set for a power steering car without using the dropping bracket. Being 70 years old sure makes any project a lot harder these days. Thanks to all.
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I don't know that I'd be that hasty to replace the CJ manifolds. They aren't as restricting as you might think on a mildish engine like yours. I think you have a decent collection of parts, though the cam is milder than I would have used. I suspect you have more power potential than you think and could benefit from fine tuning what you have. You shouldn't see that low vacuum and rough idle with the parts you have.
If it were mine, I think I'd look into adding a FiTech injection system in place of the carb and get the tune sorted out with real data.
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All good advice here.
Need to know the intake you are running, however, general rules of thumb
1 - Make sure the ignition curve works for the build and make sure you are getting full throttle
2 - Headers and a real good dual exhaust with crossover helps
3 - If you are running a Performer intake, I'd ditch it and get an RPM or Streetmaster/Street Dominator (I may even do this before headers, but on the fence)
4 - After that, or during an intake swap, I'd ditch the 268. It's really the bottle neck and not enough cam for your use IMHO. Something like an XE274H as an absolute guess, with the right valve springs and things matched above, will make it a monster and likely be a little less hell on the tires down low
I like the EFI idea, but 216 @ .050 cam is real mild, even with a good set of heads
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It needs more cam. If you only did one change that should be it.
Nothing wrong with the RPM intake or carb or heads for that matter.
The exhaust manifolds aren't terrible but headers will make more power. The 3.50 gears are fine if the tranny is the 2.78 first. If it's the 2.32 it is a too tall first gear for my liking.
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Rough idle and low vacuum on that mild cam literally screams vacuum leak or retarded cam timing.
I would be checking for both of those before moving ahead on other changes.
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2X to what Barry said as those were my thoughts too. Warped intake, machined decks, steel locating pin, intake gasket valley side tabs for the OEM gaskets, retarded cam timing are all possibilities.
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X3 for Barry
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I don't think I have a vacuum leak. Pvc and brake booster have been plugged, as well as a manifold and gaskets changed from PI to edel rpm, no change still 13in steady. Checked with two different gauges. did not degree cam, always just aligned the dots. If I am a tooth off would it still run ok? Need to change balancer anyway the 67 PI balancer is wobbling. Bought a professional products balancer a year ago to replace. Looks like I need to pull front cover to check cam and if going that far am going to change cam. Have a 274XE cam in my mustang 351w, changed from 266 crane , made a different car. Someone suggested for FE 274 XE, would the edelbrock valve springs handle that cam and do I need to change to adjustable valve train. Have stock now with POP end stands. THANKS!
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So lining the gears up dot to dot would get you pretty close, nothing like being off a tooth. Off a tooth, something would likely hit or tun far worse. Barry was referring to a very late ICL due to tolerance stack, errors in machining, or even accidentally picking the wrong slot in a multi-key bottom gear.
One thing you may want to do is check TDC with a piston stop to see if your balancer swap has your timing off. If you haven't done that before, you screw a stop into a spark plug hole, by hand, turn the motor until it hits, mark the balancer at the timing pointer, then turn the motor the other way until it hits again, mark the balancer. TDC is the exact middle between those two points. If you are off, timing could be off and make it pretty snoozy
Didn't realize you had an RPM at first, but since you do, assuming timing curve is right, I say cam change next. However, I agree with Barry that low vacuum is odd with a 268H and a 428. Maybe try a second gauge, then advance the timing 4-6 degrees and see if it changes (not saying to run it that way, but would be interesting at idle)
As far as the XE274H and current springs, I would expect them to work fine, but, as I told 427HISS, you should really check at least one. You are going from .494 lift to .565 My hunch is you'd have an open pressure increase of about 25 lbs, but you need to check, to include checking for coil bind and valve clearance and maybe use a +.050 keeper during cam break in. I would recommend degreeing that one though if it's an option
I do not think you need to change to adjustable valvetrain for a 274H, in fact, in most cases, I'd recommend against it because stock rockers work so well.
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I kinda put the low vacuum on the back burner, but looks like I need to address it first. I will get back to the forum to let everyone know what I found. It will be a while until the weather warms. THANKS!
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I strongly agree with checking for TDC, you say that your banancer is wobbling, so it also may have rotated on the hub section, which may mean your ignition timing is way off, which could affect the idle and vacuum reading. The 268H in my 69 Mach 1 428CJ idled almost like a stock cam, in drive at 700 RPM with a stock torque convertor, and 17-18 in vacuum. When you installed the 268H cam, did you check for lifter preload? Excessive preload could contribute to low vacuum and rough idle.
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I did check for preload, had a adjustable oem set on at first, tried a lot of preload to no preload, no difference in vacuum. ended up shimming rocker stands about .008 since the block was milled the same amount and using non adjustable rockers with POP end stands. The timing chain gear was cloyes brand with only one slot. Tried to different vacuum gauges, read the same. I am going to pull the front cover when weather warms, and if I don't see anything will give a shot degreeing the cam, will be a first for me. I do have a summit degree wheel, but will have to be educated to use. THANKS!
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Somehow I think your initial timing is off .Before you change harmonic balancers see what your timing is set at if is 10- 12 degrees try 14-16 and see if it doesn't run better. You will be able to see what your total timing is with that new harmonic balancer that should be 36-38 .Maybe a recurved distributor is in your future .A fellow on this forum(Faron) does them .I had a 428 cj similar specs. as yours it was a strong runner with probably 18 on my vaccumn gauge.The cam was 218@ 0.50
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First impression would be to ditch the power brake setup, unless you have some need to keep the car original. Put manual front disks on it, change the pedal to a manual brake pedal and then any vacuum issues go away except for tuning.
Balancer - Agree, you need to make up a piston stop from an old spark plug and verify TDC. I have found over the years that a lot - most - aged factor balancers are off. Sometimes way off.