FE Power Forums
FE Power Forums => FE Technical Forum => Topic started by: Thumperbird on June 03, 2018, 10:55:15 AM
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My newly built 445 is running rough on anything but mild accleration, looking for ideas?
445, modest cam from Lykins, edelbrock air gap dual quad, custom adaptors for bk/bj carbs.
Aluminum heads, good headers, target was 10.2:1 compression.
Torque converter might be a little too loose but hard to tell without much torque.
Broader trans. will not easily drop down in to 3rd for some reason.
Here is how it behaves:
Starts well, idles ok but a bit rough, not familiar with a build like this so hard to judge
Temp. is good, oil pressure is good, no reason to believe there is a bad cylinder or ? but not sure yet, have not done cylinder by cylinder compression check yet
Very poor low end torque, will accelerate more or less smooth if I am easy on the throttle but if I try and get on it it just starts to shake a shutter quite a bit, not a bog, but gets rough and not much power, will not wind out at all
I feel like it is rich but no Air/fuel sensor yet, plugs look clean, almost too clean but only have a few miles on it.
No smoke out the pipes, does not smell overly gassy at idle at least.
Revs in park just fine.
Confident initial timing is close, around -15, seemed to idle slower and rougher at 15 but was not sure 20 initial was a good idea. All in at around -30 right now, probably at around 3000rpm's black bushing in MSD pro billet
Dual quad but adjusted slip linkage to take second carb out of the picture for now, this helped a bit
No changes to carbs yet, idle vac is -14 so I think the power valves are staying closed
A little but not much response from idle mixture screw adjustment, not as much control as an old 390 I had way back in the day
Before I start down the power valve and jet routine was looking for any and all ideas as to likely condition of tune from this description.
Thanks.
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Give it some fuel. A stumble is generally a lean condition and everything that you described (very clean plugs, no smoke, etc.) point to that as well.
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As far as cam is it solid , hydraulic ?. If solid are valves adjusted properly. Was piston to valve clearance performed. If you put your hands over the carbs does the idle change? Just a couple of quick things to check. Is adapter definetly not a vacuum leak
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How's the squirt from the pump shot(s)?
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Hydraulic roller, comp cams, morel lifters, Harland Sharp Rockers, all alignment items in valve train looked great, set rod length so adjusters are as high as possible, sweep across valve tip is centered and nice.
Piston to valve clearance good.
Degreed cam, it was dead on.
I believe I did a proper job of preloading the lifters, I do maybe hear a mild tick but not sure, they are very close at least.
I think all adaptors and carb flange joints are nice and tight, engine is dry all the way around so far.
Squirt looks strong at least when in park.
I believe bowl fuel level is good and mechanical pressure never sways from about 5 psi.
Vacuum is stronger than i expected, maybe power valves are coming on too late? Stock BJ/BK's are 6.5 I think.
When I stab the throttle in park vac. drops to 5.
Thanks.
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Which heads are you running? Almost any will like a little more total than 30. If Edelbrock, get it to 36, if BBM and tight quench, add 2-3 degrees. Readjust idle speed, then a/f again to best idle and see what it does
Don't let the PV get in your head yet, it'll get you going down a path that won't help. This sounds like timing or carb adjustment to me.
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Did you check for pushrod binding on the rockers? With the adjuster at the highest position, the p/r cups may be hitting the rockers. You won't necessarily hear it, but it will wreak havoc on everything.
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Shudder is normally lean.
Stock bj/bk came with .025 shooters, I find after 50+ years of sitting around the actual holes are more like .020 due to shellac.
I typically drill them anywhere from .025-.035 depending on usage, most normal engines end up at .028, of course you have a pretty cavernous intake which will require a large pump shot. Also be aware that there should be NO gap between the accelerator pump screw and pump arm. For some reason folks still set these with a .015 gap which makes no sense.
This will cause the exact scenario you are describing (as will a dozen other things, but this is an easy check)
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Edelbrock heads, stock valve size with good valve job.
Port matched to intake and exhaust, cleaned up runners and bowls a bit.
Yes, made sure I had clearance rod cup to rocker, adjusters are out about 1 thread max I would say.
No gap on accelerator pump, looks like it starts coming in immediately.
These are noew carbs from Carls.
Things are getting more fun now, in a good way...
Found that one of the floats was stuck on the second carb.
A quick tap with a wrench fixed that, this made me want to bring the second carb back into play so I adjusted slip linkage so it starts to come in at about 1/4 main carb throttle. This woke it up a lot, of course there was no second carb shot happening, big problem. I also added some timing, around 36 all in.
I think it wants even more fuel the more I play with it, very thirsty it seems to me.
Idle vac. is a little under 10 now so will have to review power valve setup I suppose among all other carb and timing stuff of course. Low end is still not great but not nearly as poor.
Slight hesitation still at low rpm launch but at part throttle it gets up and goes.
I disconnected the trans modulator for now, this stiffened up shifting a bit.
I will measure the shooters and see where they are at, one side on the second carb does seem a little more weak than the others.
Thoughts on jetting, accelerator pump cam or pump shot?
Thanks much everyone.
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Thoughts on jetting, accelerator pump cam or pump shot?
Thanks much everyone.
White cam #1 position, 66jets, I'd start with a .035 nozzle and go lower until a stumble is found. You have a really large open intake and I think you'll find .035 is going to be far closer to happy than where you currently are.
Also BJ/BK's are really lean in the secondaries, like .059 main feed and .029 idle feed.
On my custom 2x4's I run .076 main feed and .035-.040 idle feed
Remember, the "magic" of bj/bk's is that they worked well with a stock 427, change the engine, cam, intake, cubic inches, etc, all of a sudden the magic vanishes and they are just high priced 600cfm carbs, with a cool list number. My honest advice to anyone that doesn't need bj/bk's for a number matching build is to either sell them or put them on the shelf and make your own 2x4 carbs that you don't mind drilling on (or buy Qf's from Barry/Brent/Blair that have adjustable restrictions). I'm not aware of the reproduction calibrations, so i can't comment further on that, but I assume it's close to the original.
(anyone have some repro bj/bk's I can borrow for a couple days?)
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edelbrock air gap dual quad, custom adaptors for bk/bj carbs.
The adaptors to make the Holleys fit that air gap intake can screw up fuel distribution as well. Making calibration even harder to understand and far from normal procedure.
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The .015" on the accelerator arm clearance is at WOT, so that the arm doesn't close the little pin holding the ball in place and shutting off the fuel supply hole. No fuel will come in, or not enough if that happens. Joe-JDC
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Of course Joe.... yet I still see people suggesting .015 clearance between the arm and adjusting screw, it's a pretty common bit of misinformation.
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Additional info, may be of no help. This carb talk reminded of a thread starring Chipmechanic. Dug it up. https://www.fordfe.com/bj-bk-carb-specifications-t49374.html
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Felony, his measurements are way off. The ifr and emulsion specifically. I don’t think he realized the ifr is inside the idle well.
He wrote:
BJ carb...List 2805
Primary main air bleed .030"
Primary idle air bleed .062"
Secondary main air bleed .025"
Secondary idle air bleed .028"
Squirter .025"
Primary Jets 66
Transition slot width .025" all 4 corners
emulsion jets .029" ...both sides both jets
kill bleeds .028"
idle feed restrictors .042"
Power valve channel restriction .043"
secondary metering plate same as 600 holley
PV not marked but seems to be same as 85. Pretty stiff.
straight leg boosters, standard 600 holley sized plates and venturi
yellow squirter cam position 1
Several errors like assuming the metering plate is the same... it is NOT even close.
I Measured with Starrett Pin gauges, not with pin drills, which are very inaccurate.
List number C3AF-9510-BK List 2804 and C3AF-9510-BJ List 2805
Type 2x4 4160's
Primary
Float Large brass, side hung
Booster .140 Straight leg
Pump nozzle .025
Pump type and cam White #1
Idle air bleed .063
High speed bleed .031
Metering block# 4033
Main Jet 66
Power valve 6.5
PVCR .042
Emulsion 2 @ .028 in each airwell
2 @ .026 in upper dogleg feeding emulsion tubes
Kill Bleed none
Idle Feed restriction .026 in idle well
Needle and seat .097
Venturi size 1 5/16
Throttle plate size 1 9/16
Secondary
Mechanical or Vacuum? VS
Spring color Yellow
Diapghram length 2.050
Float large brass, sid hung
Booster .140 Straight leg
Pump Nozzle na
Pump type and cam white #1
Idle air bleed .028
High speed bleed .025
Metering block/plate# #13
Idle Feed Restriction .029
Jet size or Main restriction .059 (often quoted as 63 jet equivalent, not certain on that)
Needle and seat .097
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Drew, are you referring to original BJ/BK carbs, or the repros? While they didn't specify, I think the ones he got from Bob were the repros.
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Felony, his measurements are way off. The ifr and emulsion specifically. I don’t think he realized the ifr is inside the idle well.
Well, I trust you more. I mean, he worked on potato chip machines and you roam the high seas in search of Megalodon and the Giant Squid. Easy choice! 8)
Seriously, I am trying to get re-educated about Holleys to a higher level than I once had. Between all the loose and on-car carbs, I betcha I have at least 100 of them. I monkeyed around a lot in the old days with jets and pump cams and shooters and all, but not too much beyond. I know EFI is the big thing these days, but I'd rather tinker with old tech.
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Drew, are you referring to original BJ/BK carbs, or the repros? While they didn't specify, I think the ones he got from Bob were the repros.
I’m referring to originals which I thought chip mech was as well. Either way a .042 ifr would be crazy.
I’m with ya felony. Tho often frustrating I prefer old tech as well.
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Moving accelerator cam from 2 to 1 definitely helped with a low speed launch, less hesitation.
At the same time though I feel like I lost a little bit of power going into second around 4800 RPM's.
Almost like I traded performance from one to the other.
Have not messed with any jets yet, trying to get as far as I can with existing setup and go from there.
Idle is still rough but better after playing with mixture a bit, I noticed that choking the idle air bleed did make idle worse of course, makes me think I should try going the other way on that as previously suggested. Have not messed with accelerator nozzle size but that is next I think.
Thoughts on this? Thanks.
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@Drew - thanks for posting that detail about the BJ/BK specs. Well said re the high-dollar 600 Holleys. Other than the linkage I've had good luck making dual quads from just about any twins, its just a matter of setting them up. On the secondaries, my 1964 shop manual says the BJ/BK got a #11 plate, which is a secondary hole of .079". Actually a bit richer than the typical 600 Holley. But other BJ/BK sources I've seen show those very lean holes in the secondaries.
I see a lot of "dual quad" calibrations with leaner secondaries (like the carbs Edelbrock sells to go with this intake!). Not sure why there would be such a trend if there is one. I did find that my best jetting for twin AFB's on my FE was a little leaner than the best setting for either of those AFB's when used as a single-4v carb. Hmmm. This was all done using the GTECH, not a fancy O2 meter.
@Thunderbird - We once had the problem you describe on our 4100 autolite powered truck. It would cruise ok, but if you got into it at all, it would start "chugging" like it had about 3 plug wires off. Turns out, the booster assembly had pulled loose in the secondary (yes, they are multi-piece if you look close). Never seen that before. So of course the secondary main system was really screwed up * that's how it ran.
What I always do is try each carb of a dual quad setup first as a SINGLE carb on a good running 4bbl engine. Make sure I'm totally happy with it as a single 4bbl before I put two of them on and then cant tell who is the bad guy. Not sure if you have another (old) car you could try that on with each carb.
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Werby brings up a good point. I build about four sets of 2x4 1850’s a month. While testing out often they’ll be off base. I also tune each one on my truck when that happens. Easier to narrow down a minor issue.
Werby, maybe they changed the plate at some point? On my custom carbs I typically wind up larger on the secondary.
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Been playing some more.
Here is where things are at, and what I am planning next, looking for feedback.
Set rev limit on my MSD high, it was choking things off almost a 1000 rpm before set value.
Learned something after this as I had not run it up in the 5000+ range much.
Seems to run lean at wide open throttle but here is what is interesting, I suspect it's the secondaries coming in kind of late but quite frankly never experienced this before. Running rich and a little choppy still at idle.
It pulls fairly hard from 3000 to say 4500, then seems to soften and maybe even shudder a little, then at just over 5000 rpm's it smoothes out really well, still lean but not as much, and pulls hard to 6000, did not go beyond that.
Thinking of doing the following, want to minimize carb removals as the duals are a pain in the rear.
1. Main jets are 66, bump to 70
2. Try some softer springs in the vac. secondary diaphragm, I think the thing is a thirsty pig and starving for fuel at higher rpm's
3. Squirters were bumped to 32 a while back, going to try 35's
4. Check on secondary restriction size when carbs are off and go from there, if they are the small flavor will drill them out
5. Double check transition slot and set them up so they are less than square and secondary is more in the game
Thoughts everyone?
Thanks.
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Do not know if it relates...
On dyno when running vacuum secondaries you will often see them roll rich just before the secondaries open up - probably as air demand approaches the limits of the primary side. Then as the secondaries open they will have a lean hole as the rear main circuits are activated by airflow. So you get a few hundred RPM of "upsie-downsie" before things stabilize. Changing the secondary rate springs until the opening point most closely matches demand cleans this up, but might not be reflective of what it wants "in the car". You could be moving through that fuss point.
On dyno I will sometimes wire tie the secondaries to open so I can isolate WOT A/F tuning from the opening rate tuning.
The .015 pump setting is at WOT as Joe referenced, but I have also seen those set wrong. On race only applications I am guilty of doing that - setting them loose - so that the full pump shot is available when leaving off the converter at higher throttle opening positions (like 4000 or so). Otherwise you have less pump shot left when you go WOT. On street stuff this approach will not work - you need to set them up as Drew says - no clearance at idle.
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With as much money as you have invested in that engine you should have a wide band in the exhaust. If the carbs are off you can ruin a new engine pretty quickly. We see it all the time at the engine shop. Guys pay $10K to have a performance engine built and then they don't tune the carb and before long they are back in the shop with cylinders wiped and valve guides shot.
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An easy thing to try:
Lock both secondaries SHUT (easy to do, no need to pull carbs) and see how it behaves a a 4v like 0-2-0-2 barrels.
Then leave each one locked shut but let the other one open (so you have a 6v like 0-2-2-2 or 2-2-0-2 barrels.
Easy to try and you might learn something qualitative.
Agree on the wideband though - I don't tend to run $10,000 plus engines but if I did it seems that would be a small added expense to get all 8 barrels happy.
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thoughts:
-Most engines seem to like the short yellow VS spring in a dual 600
-I rarely exceed 66 or 67 in primary jet in a 600cfm carb, I'd leave finding the lean limit in jetting until all the other issues are worked out.
-If you aren't totally redoing a carb and just changing jets, I don't see the need for an O2, seems lotsa folks chase their tails, paying more attention to a gauge than to how the engine is running. Pull some plugs, make some guesses.
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Thank you for all of the feedback and input.
I do have a wide band installed, using it for reference to make sure things are not getting too far out of line. A/F is generally sitting between 13 and 14 for most driving conditions, 12 for cold start and after letting off the throttle, up to 15 under hard acceleration. It bounces around a bit at low RPM, due to the high overlap cam I am told. Trying to stay on the slightly rich side of things all the time until I get it dialed in.
I wish there was a way to delay the pump shot, have done a few 3000 launches and it goes fine but wonder if some extra fuel early on could compensate for lazy mains or ?
I will play with secondary on/off and spring setup before the main jets and see what happens.
As for the rough idle, what is the collective opinion on setup of primary and secondary in terms of the transition slot, etc.? From reading, it sounds like on a dual quad, a good starting point is less slot exposed on both carbs than say a single 4V. I feel like the air bleeds are not quite right in my setup, wondering how much of that I can compensate for with transfer slot and secondary setup?
Also, am I crazy to think that this thing is and will pull hard beyond 6000? I did do a fair amount of work on the heads and intake runners but nothing too crazy.
Thanks again everyone, I need to get comfortable with spending more time tweaking and testing, just tough to get used to testing at the higher RPM's in a suburban environment.
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I need to borrow a set of these replicas and record the calibration. I understand they
Are different than the original, which I guess doesn’t make them replicas.
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Drew,
I would have no problem sending them to you this winter, by then I should have dialed them in better so there would be a reference to a 445 stroker build, would of course document all changes I made.
Driving season is so short where I live that I want to just keep tinkering and taking some joy rides for a while here.
Starting to wonder just how impactful the extra large plenum volume is to carb. behavior.
Thanks.
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Cool. Lemme know, I’d be happy to pay shipping both ways for the knowledge.
I suggested the larger pump shot due to that large plenum. I’ve never messed with that particular intake, but Jays dyno testing showed no major abnormalities.
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thoughts:
-Most engines seem to like the short yellow VS spring in a dual 600
-I rarely exceed 66 or 67 in primary jet in a 600cfm carb, I'd leave finding the lean limit in jetting until all the other issues are worked out.
-If you aren't totally redoing a carb and just changing jets, I don't see the need for an O2, seems lotsa folks chase their tails, paying more attention to a gauge than to how the engine is running. Pull some plugs, make some guesses.
X2 on the O2. Reference - with the dual Ed 600s that I run on the 302, the A/F from the Innovate interface was good, 13ish mostly and drove decent. But to get best performance and MPH at the strip, drilled both shooters to .035 and went up 4% (Edelbrock one step) in fuel on both ends of both carbs. O2 is a good tool, but you still have to try stuff.
Trans not shifting into 3rd well - that sounds like vacuum modulator, either you have really low vacuum in the intake or the hose/line has a leak.
It does sound like carb(s) issue. For fun, I have two same frankencarbs here - ProForm 750 DP centers, QFT blocks, billet 4 corner base plates, etc. Same jetting, same IFR (33 IIRC), same PV. Put one on the dragster - blubbers, breaks up at RPM, not the least bit smooth, sounds like it is loading up. Swap on the other - clean idle, clean above 3000 (big solid roller in the motor). Go figure. Says to me that there is something really out of whack with one of the QFT blocks. I have a ProForm purple block with the same deal - used it as the front block on a 750, never worked well. Changed to a stocker from another 750DP - ran well.
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Thank you for all of the feedback and input.
I do have a wide band installed, using it for reference to make sure things are not getting too far out of line. A/F is generally sitting between 13 and 14 for most driving conditions, 12 for cold start and after letting off the throttle, up to 15 under hard acceleration. It bounces around a bit at low RPM, due to the high overlap cam I am told. Trying to stay on the slightly rich side of things all the time until I get it dialed in.
If your wideband is accurate you are running lean under hard acceleration. You should be shooting for 12.5: to 13:1 at wide open throttle, from 3000 to 6000 RPM. Sounds like you are way higher than that. I'd bump the main jets up six sizes and run a few more wide open throttle tests. Do it in a higher gear so that the wideband has a chance to settle down. You might have to go even more than six jet sizes. If I saw those numbers on the dyno I'd be fattening up the carbs a bunch.
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You would adjust jet even if the cruise afr is ok?
Or would you look at the PV opening point and pvcr size?
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When tuning Holley accelerator pumps you have a LOT of variables to tinker with.
When you work with a "fixed" pump volume (like the "30cc" standard pump) and a single chosen pump cam, changing the pump shot orifice changes the amount of time that a squirt takes to deliver - it does not really change the amount of the fuel. You will get +/-3cc of fuel provided in a short time or a longer time - a lot "right now" or a little over a longer period.
You can change the timing of that fuel and the available volume of fuel by using a different pump cam - some cams provide a longer stroke using more of the available pump capacity. Obviously some of the cams provide more or less fuel at various points in the throttle rotation as well, and have two or three possible clocking locations relative to the throttle blades.
That spring on the pump arm will also mitigate the opening rate a bit when you slam the throttle open no matter how fast the cam tries to open.
What this means is that you can try to "fix" a problem by throwing a ton of fuel at it with a big shooter and either have it work - or end up with a rich hole followed by a lean hole as the throttle opens. The only thing you can do is to buy the assortment of cams and a few shooters and try stuff.
Pump tuning is not really difficult - it just takes iterations until you are happy with the results. As Drew said - do not fixate on the O2 numbers for acceleration behavior - work on getting it to run good. That's what really counts.
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You would adjust jet even if the cruise afr is ok?
Or would you look at the PV opening point and pvcr size?
Darn near nobody ever does it that way - - but they SHOULD. The PVCR is effectively a high load & WOT jet and gives you exactly what you desire - lean cruise and richer at WOT. On some Dominators back in the proverbial day, they had the PVCR as large as the main jets and needed to run a low restriction power valve for them to deliver enough fuel.
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You would adjust jet even if the cruise afr is ok?
Or would you look at the PV opening point and pvcr size?
Darn near nobody ever does it that way - - but they SHOULD. The PVCR is effectively a high load & WOT jet and gives you exactly what you desire - lean cruise and richer at WOT. On some Dominators back in the proverbial day, they had the PVCR as large as the main jets and needed to run a low restriction power valve for them to deliver enough fuel.
I do what Jay said while tuning, with the cheap old 4160 carbs I deal with, you can change the primary jets but the other stuff, once you drill it, its drilled. And if you drill the secondary "plate", you have to buy a new one which costs usually more than I paid for the whole carb. I know, I'm living in the past, I don't think I ever paid more than $35 for a 600 Holley (and that was a 390gt carb).
I agree that seems lean - as I stated above, I've seen two specs for the BJ/BK carbs. One has an .079" secondary hole, the other has a .064" hole which is of course way leaner. WAY leaner. If you have the "lean" spec BJ/BK, it may well be way too lean in the secondary. Again you could block the secondaries shut and see what the wideband says. You'll be down about 35hp but running on those pure 66 Jets and their PVCR's. That should be pretty close, unless you're running open headers.
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How stupid is this idea? Be honest.
I have 2 50HP each nitrous plates installed, could I just activate the wet side fuel delivery for a quick blip of fuel while under hard acceleration and see how it behaves?
I did not record it but I think the AF went from just shy of 15 when it was struggling under 5000 rpm's to just north of 14 when it smoothed out quite a bit over 5000, nothing is calibrated here so just relative info. at best. I asked Carl's Ford for a build rundown (2nd request) on the carbs and will figure out best way to optimize AF at full throttle.
The thing overall is a gas pig so if i can do it without running rich all the time that would be best.
Thanks.
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Not sure how many people are running Holleys on the Edelbrock dual manifold.
Is it possible that this combo. is just more thirsty or behaves somewhat different than other dual carb/intake combos or a single on an RPM air gap? Or am I just dealing with typical setup issues?
Can anyone chime in on variation they saw running a single Holley on the single Edelbrock air gap as opposed to single Holley on other similar manifolds?
I know the duals present a whole new picture but wonder if there are any correlations to what I am seeing in the single carb. world for various intakes, i.e. the need for lots more fuel on the top end for the air gap on an otherwise middle of the road 445 stroker?
Heavy car playing into this combined with a wide ratio C6 giving me some unique challenges until the thing really opens up?
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How stupid is this idea? Be honest.
I have 2 50HP each nitrous plates installed, could I just activate the wet side fuel delivery for a quick blip of fuel while under hard acceleration and see how it behaves?
It's pretty stupid ;D ;D Just kidding, but activating those plates on the fuel side would give you way, way too much extra fuel...
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Not sure how many people are running Holleys on the Edelbrock dual manifold.
The answer to this question is probably "one" - and its "you".
Those wide angled spacers are introducing a wild card variable that nobody has worked with...
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Not sure how many people are running Holleys on the Edelbrock dual manifold.
The answer to this question is probably "one" - and its "you".
Those wide angled spacers are introducing a wild card variable that nobody has worked with...
Sometimes the weird stuff doesn't work. I've built plenty of weird stuff over the years that didn't work so I'm familiar with the drill.
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These guys (below) have some good points.
I looked in the Gonkulator database at all the Edel 8v RPM intakes I have in there - nobody running Holleys, all AFB-style.
I have seen a phenomenon maybe like "Wind Shear" in intake design - I designed a home-made "Trips" intake for a straight-six a while back. It did funny stuff at high rpm (high means near 4000 here) - started to go flat, skip and miss - throttle plates of the added carbs too close to a wind shear area. I was able to make it go away but it took some redesign. Maybe something like that going on in the spacers?
A way to find out: Why not try a couple Edel/Carter AFB or AVS carbs on there, without the spacers. In my experience, twin Holleys will outrun twin AFB's by 1-2 carlengths, but so what? The twin AFB's still run good, smooth, right up to the top. It could help isolate the problem.
But first I'd block those secondaries shut and try it. Then pull em off and see what secondary "jets" (holes) are in there.
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Barry R:
The answer to this question is probably "one" - and its "you".
Those wide angled spacers are introducing a wild card variable that nobody has worked with...
AndyF::
Sometimes the weird stuff doesn't work. I've built plenty of weird stuff over the years that didn't work so I'm familiar with the drill.
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Like i stated before in post#10. Edelbrock air gap dual quad, with custom adapters for bk/bj carbs.
The adapters to make the Holleys fit that air gap intake can screw up fuel distribution as well. Making calibration even harder to understand and far from normal procedure.
On the discussion Holleys vs Carters or Quadrajets by the way, they are all carburetors working and depending on the same physical laws, cfm is still cfm. Yes they have different types of boosters and power enrichment provisions and so on, one just have to understand how to work them properly to get the best out of them. The Holleys have there "simpleness" ore at least a broader understanding among the Hot Rod and race crowd, other than that its still the cfm vs pump losses we all try to mannish best we can with out fooling ourself with a to big carb.
A little more than 25 years ago i was deeply involved in a NHRA stock legal A/SA -71 HEMI Cuda that held the European record fore 10 years with the OEM Carter Hemi carbs on it. Howe fast?? 10.71 pretty impressive at that time, with the "real " old stock rules.
Just saying, a carb is a carb one just have to figure out how it needs to be worked and if it is BIG enough.
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Thanks everyone.
I think I will try some bigger main jets, 70's, as I feel it is a bit lean at cruise as well as WOT.
When I pull the carbs for the jets I will verify transition slot setup.
I also intend to play with secondary diaphragm springs.
Before modifying the secondary metering plates I think I would drop back to a single carb., I can mount 1 without the spacer, and see how well it behaves that way though I know then i very well might be under-carbed.
By the way, I had adjusted the slip linkage such that the 2nd carb. came in sooner, this seemed to help some of the mid throttle issues I had early on. I think I will go back to normal setup on this as well, can not be good to crack the second carb. open almost right away and then of course on the top end not fully open. Maybe the larger mains will satisfy this old issue.
Thanks.
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Had very little to no time to play with carbs all summer.
Current situation is rich idle and cruise, goes way lean after a rich squirt pulse when I get on it at any rpm or gear and still shutters, bogs off the line. Scoop or no scoop makes little difference in behavior.
No jet changes yet other than going to 32 boosters, lighter secondary springs and have messed with slip linkage timing for 2nd carb. Lighter secondary springs did nearly nothing, confused by that.
Bringing the second carb sooner makes low end more sluggish. Have not tried single carb yet.
Overall still fun to drive but just not right at most throttle positions/gears with a pedal stab and likes a slow to moderate throttle push then it picks up at a nice solid and smooth rate. Smooth as heck in the driveway.
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Of course Joe.... yet I still see people suggesting .015 clearance between the arm and adjusting screw, it's a pretty common bit of misinformation.
It's SUPPOSED to be .015 away from bottoming the diaphragm @ WOT, NOT .015 clearance on the base circle of the pump cam! BIG difference.
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Of course Joe.... yet I still see people suggesting .015 clearance between the arm and adjusting screw, it's a pretty common bit of misinformation.
It's SUPPOSED to be .015 away from bottoming the diaphragm @ WOT, NOT .015 clearance on the base circle of the pump cam! BIG difference.
Another thing I'll mention here, if you run #330 pink or sometimes even the blue cam, it will bottom the diaphragm at WOT, and you won't be able to get the specified clearance. The way around this is to take another old diaphragm and cut the center out, and place it between the diaphragm and the pump well in the float bowl. Now you can adjust it properly, and you will get all the shot these two cams have to offer.
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Finally had a chance to remove the BJ/BK clones from Carl's and take some measurements.
They both look to be the same but data is for BK only so far, primary carb with choke.
My numbers should be within a thou. of actual, used high precision QB pins to mic holes.
Not super impressed with casting quality and machining, a bit of minor flash here and there on some of the ports and channels. If you happen to read this Drew, might still take you up on sending to you for review, just playing myself for now, I like to roll my own as much as I can.
Going to beat these things into submission if it kills me and dial in every little item.
Biggest surprise for me was 60 mains, wonder what the 70's I bought will do.
Never had good idle control (RPM's yes but a little rough and always rich), starting to think the power valve was maybe open causing my very rich idle.
Going to change to a 3.5 PV
Adjustable bleeds
Remove the choke
Might hack off the air horns to aid flow in my scoop
Spacers need a little work to reduce turbulence as much as possible
Thanks and here are my numbers:
List number Set came from Carl's Ford
C3AF-9510-BK List 2804 and C3AF-9510-BJ List 2805
Type 2x4 4160's
Primary
Float non-metallic, side hung
Booster .142 Straight leg
Pump nozzle shipped 0.025, 0.032 now
Pump type and cam Don't recall as shipped, White #1 now
Idle air bleed .067
High speed bleed .034
Metering block# Nor sure on this, casting id is 34R 12683B
Main Jet 60
Power valve 6.5
PVCR .032
Emulsion 2 @ .027+ in each airwell
2 @ .027 in upper dogleg (1 in each) feeding emulsion tubes
Kill Bleed Not sure
Idle Feed restriction .027 in idle well
Needle and seat .097
Venturi size 1.20"
Throttle plate size 1.50"
Secondary
Metering plate marked as 34R 9716B #6 stamped in it
Mechanical or Vacuum? VS
Spring color Don't recall shipped, lightest now
Diaphragm length 1.95" (to rod pin hole center)
Float non-metallic, side hung
Booster .142 Straight leg
Pump Nozzle na
Pump type and cam na
Idle air bleed .027
High speed bleed .032
Metering block/plate# #6?
Idle Feed Restriction .030
Jet size or Main restriction .065
Needle and seat .097
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Finally had time to finish up a few mods left over from winter, a quick update on things and though I know you all ar probably tired of the questions, I kindly ask for some dual quad tuning feedback again, let me know what you think.
Went to 12" converter, about 2600 stall, love it compared to the 10" 3100 stall.
Installed proper pushrods for rocker geometry.
Got rid of my intake oil leak and installed a pcv.
As you may recall I had custom offset spacers to accomodate holleys on an Edelbrock dual quad, these consisted of a 1 inch offset spacer and a 1 inch 4 hole spacer(2" tall), never had the low end or smooth running motor I expected. Photos attached show new spacers that have a center divider to preserve the dual plane all the way to the carbs.
Quick fuel 600's vacuum seconday, no mods so far other than turning screws
Best performance has come from no slip linkage, carbs tied 1:1.
Secondaries cracked a tad on both to set idle, primaries closed off .
Idle screws out about 1/2 turn out each.
Here's how it behaves, what next?
First, with 2nd carb set to come in at 1/3 1st carb throttle it was very rich all the time, I felt like it needed more air so here is what came next, I'm close to a nice runner at all RPM's albeit not a conventional setup I suspect but not there yet under medium hard throttle.
Idle is smooth but a little rich, AF 12/13, if I turn in idle screws I go more lean but tip in stumble is evident. Launches fairly hard, nice low end torque now.
Cruise between 1500 and say 3000 rpms is AF of 13.5 to 15, nice and smooth.
If I get on it a bit at a cruise speed there is a very brief lean out then it will go quite rich to say 11/12, will recover to ~14 after RPM's come up a bit to match the throttle position.
Quik Fuels have adjustable secondaries, does not matter much if I have them set to fast or slow I still see the rich behavior on moderate acceleration and hard acceleration until my RPM's get to say 4500 then it starts to pull very well. Timing is ~20, ~ 34 all in by 2500.
It is never a dog but definitely rough sounding at least on hard acceleration until RPMs get up there, I suspect due to rich fuel. I like the idle and cruise, very top end seems strong as heck as well but that middle ground like a downshift and put my foot in it goes rich and I can tell it is just not a clean acceleration.
What do you all think should be next move(s)?
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The first thing I would say is that your idle a/f is likely reading incorrectly due to overlap from a healthy cam. I would start by adjusting Idle for all barrels to be equal and best vacuum, ignore the numbers because the O2 sensor is seeing raw fuel
If it’s still fussy, I might consider a slightly smaller IAB if you think it’s not pulling on the t slots, if you thing it’s a slow booster, then I would likely get into the metering block
Of course, the battle axe bandaid could be a blue Holley pump cam, it hides a lot when it drops the hammer, but that’s sort of a Viking solution to a precision weapon problem. I have seen it do wonders though
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>Idle is smooth but a little rich,
By gauge or by nose? If it "smells gassy" as you described way back, that's lean - not fat. Also agree that with some overlap, your A/F or Lambda is going to bounce around. Dash gauges are dampened, using a meter right off an older heated O2 sensor shows you can't tell whats going on LOL. When I had a tunnel ram on the 302, idle/low speed performance was in the 12.5 or a bit less range. But those carbs were Eds and not a lot of overlap. Eds typically do a better job at idle/low speed operation than most Holley units because of the primary booster arrangement.
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Thanks for the feedback guys, plan to tune to vacuum this afternoon, 85 out though.
I also remember I forget to check pump setup after the last round of playing.
Puffing a little dark smoke when I idle and AF is under 11 that is why I was thinking AF might not be that far off.
What are some thoughts on the medium acceleration rich situation? Drop the mains on both from say 66 to 62?
As long as I'm in there open up the power valve port a bit?
Wanted to get a little closer before messing with bleeds.
Thanks.
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A savy eye will note the throttle plate and venturi size disparity between the original BK/BJ and the reproduction.
One is a 600cfm carburetor and one would be closer to 500.
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Drew:
I should have compared the bk/bj clones I have to the slayers before installing, did not do that, not that smart.
The slayers behave much better with minimal tweaking so far but of course with the new spacers who knows what was what.
The setup is quite different, so far finding that 1:1 linkage works best but I think I am a little over carburated now in the mid range when configured this way.
Trying to figure out why someone has not come up with an adjustable main, power, and bleed systems, does not seem that hard, too impatient to be going in all the time or drilling blanks all day.
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Drew is in possession of my BJ/BK carbs from Carl's Ford Parts. Perhaps he can unravel the mystery of crappy carbs for us all.
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In honor of Alex Trebek, Final Answer on the carb setup for the Tbird (almost).
Good A/F and response for all scenarios, a bit rich at 80 mph cruise (14), pulling like a freight train at end of an 1/8.
Just thought I would post more or less final configuration for Quick Fuel 2x4 setup using custom spacers on RPM Air Gap. Maybe it will be good reference for someone some day, I know everyones help from here got me to where this is a fun toy, thank you.
445 stroker, 10:1, good internals, wide ratio C6, 12" 2600 stall converter, limited slip 3.5 rear end.
Timing is 20 initial 37 all in.
Cam = Dur (050) 233 int., 241exh., Lift .563 int., .574 exh..
Carbs = Quick Fuel Black Diamond 600cfm, vacuum secondary. 1:1 throttle linkage, idle set with secondaries, both carbs set up identical.
Custom 2" offset spacers using standard spacer plates on either side, dual plenum is preserved up to the spray bars in top plate. Bottom end torque is strong, suspension work this winter to reduce tire spin on idle launch.
Primary
Float non-metallic, side hung
Booster Stock
Pump nozzle 0.031
Pump type and cam White #1, (added slight delay, likes a split second (A/F) before the squirt when you stomp it)
Idle air bleed .058 (stock 74)(got me to more smooth idle nice transition and 7/8 turn screw)
High speed bleed .033 (stock 31)
Metering block# Stock
Main Jet 0.062 (stock 66, good cruise A/F 16/15 for 30 to 70 mph, goes to 14 at 80/85)
Power valve 6.5
PVCR .042 (stock 51)(will likely bump this up a couple with nitrous use. 51 was rich when you hit it)
Emulsion stock
Kill Bleed Not sure
Idle Feed restriction .027 (stock 30, helped lean out transition, cruise up to 40 is in transition)
Needle and seat Stock
Venturi size Stock
Throttle plate size Stock
Secondary
Metering plate Stock
Mechanical or Vacuum? VS (adjustable)
Spring color N/A
Diaphragm length N/A
Float non-metallic, side hung
Booster Stock
Pump Nozzle 0.031
Pump type and cam White, #1 (stock pink)
Idle air bleed .042 (stock 33)
High speed bleed .033 (stock 46)
Metering block/plate# Stock
Idle Feed Restriction .027 (stock 31)
Jet size or Main restriction 0.070 (stock 74 but measured 77)
Needle and seat Stock
Thanks and happy winter!
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Good deal!
Love you calibration template btw, genius
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I wondered how you did the carb adapters, those look really tall and are they just an open area in the middle or 2 or 4 angled bores?
I looked at putting Holleys on my Air Gap but to clear a distributor the front carb can't be moved forward and that leaves the back carb barrels completely beyond the flange area.
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Total height is 3" including 2 each 1/2 inch spacer plates. Bottom plate is open, top plate is spray bar equipped.
Riser portion of spacers are 3/8" plate stock, 2" tall, 1.125" offset each.
Bottom plate and riser have internal partition extending the dual plenum, this is 1/8" sheet stock, so 2 rectangular angled bore plenum extenders if you will. All internal edges have radii and are blended to the purchased spacer plates, spacer plates are matched to manifold plenum.
Carbs stay cooler for sure and combined with the air gap the whole thing takes a good 10 minutes of cruising to get warmed up.
For the build I wanted the height did not matter.
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Like the engineering. What is the WOT A/F? Or are you still breaking in? The 14 @80mph, is much of a load taking place or is that no load cruise due to your combo?
Thanks for update.
JB
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WOT A/F is 13, power valve and secondaries are verified engaged, all secondaires open full on a hard pull to 5500 but maybe that is just a loose setup. 80mph cruise no load is 14, rpm's are about 3300, not in to pedal much though - twin carbs 1:1 linkage. A/F seems to slowly drop after 70mph to ~14 at 80, rarely run there so not worried.
If I was a pro like some of these guys I bet this setup could make some good power, it is decent down low and just loves winding out to 6k pulling hard the whole way, starts to break up around 6200. I did a fair amount of head int./exh. porting and matching, gut tells me it breathes real well. Yeah I know, gut means nothing.