WHAT'S INSIDE? -BLOW THROUGH CARBS
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- Опубликовано: 11 июл 2024
- CSU & QUICK FUEL-WE LOOK INSIDE BOTH! Kevin from CSU steps up to help our twin-TorqStorm 6.0L with customer carb. Trying to run two superchrgers with an E85 blow-through carb. Check out what happens when we throw the kitchen sink at it! We look inside the Quick Fuel and CSU carbs to see what makes them tick.
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I'm a mine ventilation engineer so airflow modelling is my game. I think the issue's you're having are at least partially related to the carburetor 'hat' you're using. It has a really sharp 90° bend that is no doubt causing flow separation and turbulence. The 1 thing that you want above all else through a carburetor and it's boosters is laminar flow. Another youtuber (Eric the car guy) had a very similar issue here: ruclips.net/video/Naj3LL-zIj0/видео.html @ 39 minutes discussion starts regarding this.)
I'd suggest trying a carburetor hat that has a better radius into the boosters. Even one with guide vanes or a large plenum (like the old Banks power hat's from the 80's.) Remove the turbulence to improve booster signal and response ;). Remember that the cleaner and stronger you can make the signal at the boosters (by improving the Delta.P between the main venturi and booster,) the more fuel you'll drag through the booster. If the air is all chopped up, no clean signal = no fuel draw. You could even go as far as having a 30cm straight pipe extending out the top of the carb into the hat to have air moving completely vertically into the boosters.
In addition. As airflow/airspeed increases at tight 90° bends, the turbulence increases making the problem worse. Just think water through a hose.
Good idea for a test. testing various carb hats ;).
The issue with AFR disparity throughout the motor would also point to an airflow imbalance through the carburetor (or really bad manifold design.) Where boosters favouring 1 set of cylinders are receiving more airflow (or at-least better quality airflow) than others. Once again leading back to the point's I made in the above post. You want equal laminar airflow though all 4 barrels. If you don't you have no hope of getting your tune on point. As unlike EFI you can't trim each cylinder individually to compensate of airflow imbalance.
Regards
Jordan
You can be totally right
Yup I thought about Eric’s dilemma right away. Richard, Change the air hat.
Airflow modeling is all well and good but there is that pesky fuel flow to deal with as well. And that is the problem Richard is having. I dont disagree that airflow quality has a direct effect on fuel flow through a carb, but there's much more to a holley 4150 carb than airflow alone. There are many ways to tune the fuel curve, independent of air flow.
Not a airflow engineer but a lot of experience with road race motorcycles with ram air systems and agree that the hat is where i would start. I think turbulence also and drop in float bowl air pressure the result. Try jamming some fuel hose onto the bowl vents and positioning the open ends of the hose to recieve a clean shot of airflow directly at the tubes. Would it be possible to rig a pressure guage into the dribble drains in the side of the bowls to compare hat with bowl pressure.
To anyone who can't find the answer.... it was the dyno fuel pump.
Had the exact same problem. LQ9 with D1SC ProCharger making 15psi. Through a Quick Fuel 750cfm Blow-through carb, Aeromotive Boost Ref Regulator, Aeromotive fuel pump,8AN fuel line, on a Victor Jr. No Cooler and 90* Carb hat. During first test run the AFR slowly Leaned to an unsafe level. Immediately started with carb tuning, and increasing fuel pressure thinking, more pressure more fuel. Increasing fuel pressure doesn't increase volume.
The fix- Change 8AN fuel supply line to 10AN. Separate fuel supply lines from the Regulator to Front and Rear bowls on the Carburetor.
I didn't see how yours was set up in the video, but sounded like the same problem I was having. Thought I'd share.
Most people do not comprehend how high the fuel flow requirement actually is at maksimum horsepower. A full tank of fuel last only "a couple" of minutes at 1000 hp on E85.
Extend the vent tubes into the 90 so they pick up boost pressure earlier at the bonnet. This increases the pressure in the bowl sooner and in turn assist in allows easier flow out into the engine. It creates a pressure difference. Aircrafts use airspeed tubes for this purpose
Great video Richard! These are getting more and more interesting
I run Vent tube extensions on mine. The extensions down into the carb hat more than half way. I was able to jet back down on the carb for street use. The extensions allow it to pull more fuel through less jet. I also run AN 10 line to 8AN with fuel return to tank.
I just saw this vid and thought exactly the same thing.
Seen this once before. The elbow on top of the carb is screwing up the airflow. Get one with more of a radius to turn the air into the carb. Good luck. If you guys can't figure this out, the rest of us are screwed.
Thx. For all the great info. And videos. Keep up the great work. Love your videos
Unmetered air could be introduced to the engine? I know it sounds simple but I would be searching for vacuum leaks or some other source for the unmetered air. The fact that you’re seeing two different air fuel ratio’s on different banks of the engine should give you an idea where to look.
Carb hat turbulence not letting the boosters do their job when the air really gets moving. Perhaps trying an extreme velocity type hat or one with a divider to split the air evenly.
Worth looking at the sdce carb bonnet, and the 1957 ford paxton blowthru bonnet. Both deal with hood clearance issues --since you cant have a 15 plus inch verticle tube--by chokeing, and equalizing airflow across the carb. The studebaker and early paxton gt350 carb boxes worked too, but were a crude yet reliable idea that could be pushed to production quickly.
I agree with you on most your changes, but we use e85 on top of a 177 Weiand using boost referenced bypass reg 3psi to 13psi and a 130 gph mechanical pump. (10psi boost)We are worried about lemonade (bubbles) in fuel bowl at high rpm. This is why I suggested duel needle bowl lower fuel pressure and help fuel level in bowl. Love your content thanks GM engines.
Excellent, great explanation! Keep it up Richard.... We are referring to this series that you have been doing as the Bible. Excellent excellent work thank you
I would like to see a Holley X intake manifold with the twin Torqstorms SCs.
Check intake for vacuum leak or any other vacuum leak we ran into the same exact issue on our blow through 406
I have a setup recommendation that might work better. Use a tunnel ram intake with dual carbs and run individual intercoolers for the blowers
Try to externally boost reference the carb, hook up the boostreference line to carb and regulator pre intercooler. If it's still leaning out, put a tube with a funnel pointed towards the flow in to the charge pipe ore intercooler. This worked great on a pair of dellorto's i had back in the day! The sweeds call this doping the carb😁
Thank you for the update.
I would try bowl vent extensions and point them into the path of the incoming air that should richen it up usually
#1 split flow hat (stops swirl)
$2 jet extensions
#3 dual jet bowls (big help)
#4 boost reference power valves
#5 shorten bowl tubes
$6 boost referenced fuel regulation
#7 bigger boosters
that and a couple of sizes up on the curcuits is all the magic I got
ENOUGH FUEL PRESSURE.
DYNO FUEL PUMP
I agree, it's the hat. Anytime I run more then 8 lbs of boost or so the carb hat or enclosure box has to be the proper design. I recommend the Paxton power hat. Works well at that boost range. I've also had some success using a screen in the airflow like a boat filter. Torque Storms hat is supposed to work up to 12 lbs. I would think you should have one of them to try. Thanks for the vids!
We've run the carb and hat successfully many times
@@richardholdener1727 But the fuel is different. Wouldn't that make a difference?
I tune an X Nascar Chrysler W8 with a Procharger and one of Kevin's carbs for drag racing.
It started out as gas motor carb combo with an inner cooler which worked Great.
Last year we has Kevin convert the carb for E-85 and it took me months of trial and error to get ahold of it. Same issue as you way too lean up top.
The things I did that helped most were, had Kevin send heavier power valve springs along with me drilling and tapping both front and back metering blocks to accept 4 metering jets each. That allowed better fuel control as the boost came up which made the biggest change. On the street it made driveability way better.
I like you have1 bank running leaner and my explanation for that has to do with the hat and squirters. Watch any video of a dyno run with a cam above the carb and at some point you see the squirters adding fuel to each venturi. If the hat pushed air in vertically all would be good but like others said your asking it to make a 90 deg turn and things get unhappy.
My plan this year when we get out of our houses is to put a Snow Performance meth/water system on with a shear plate under the carb. That will add fuel, cool the incoming charge and with a 2 jet plate allow me to add more fuel to the side that need it.
If that doesn't work it will get a Haltech 2500 EFI system.
20 years ago when I played with boosted cars on OBDI and you couldnt tune them we would run cold start injectors off pressure switches. Boost would hit whatever PSI and the injector would turn on. Dont know if that would work
Set a boostreference pickup further up in the chargetube, with a pitot tube facing the airflow.
For both floatbowl and pressureregulator.
I have not read the comments to see if this has been figured out yet but your issue is likely velocity through the venturi. This is only encountered on a blow through blower application. Put a anemometer in the plenum to measure airspeed and you will see it slow down and begin to stall as boost increases. This cannot be checked with a hot wire maf because of the evaporative cooling from the fuel, a vane air meter may work. As air velocity drops fuel distribution becomes an issue and vacuum signal through the carb drops. You have a combination that is completely filling the cylinder with pressurized air before the intake valve closes. You can mitigate this problem by reducing lsa to increase overlap, Closing the intake valve before air speed stalls or a combination of both. Or just use port injection......
I had this problem more than once. I fix every occasion with efi. However I believe it’s in the hat. Try putting like a 6-8” spacer between the hat and carb.
The boost in the intake manifold could be pushing back or negating fuel flow from the carburetor versus fuel injection which is sprayed in or near the combustion chamber under pressure. You may have to go bigger on the carburetor to catch up to the fuel injectors.
Richard, I was beginning to worry in the absence of a video for today. Not to be diappointed. Thanks
Can you build a bigger plenum on top of the carb? Or straighten the air out coming into the carb?
Richard , you could extend the float bowl vents into the snorkel of the hat using 5/16" tubing into steadier boost pressure in the boost tube . This will increase the pressure in the bowls at high air FLOWS . MY to cents
Yep! Your right. I had a setup that wouldn't make it out of the driveway with massive jets. Added extension and it drove good but was pig rich under load. Worth a shot anyhow.
we did run extensions as indicted in the video
That would help with the boost charge for sure
Vent tubes for sure
A cross into the carb hat intake to stop any vortex effect maybe and also timing bank to bank is the same ? That fried ecu might have other issues causing a timing difference bank to bank perhaps ??
As for the bank AFR disparity, maybe a symptom of the fueling limit, one side sees a little more vacuum or has an ever so slightly larger jet, causing that side to rob the other. I'd definitely lean towards that answer if the disparity gets worse as the HP numbers go up. I don't know if there are separate bowls for each side, or two bowls/floats that are just shared. Would be interesting to tinker with.
Some good thoughts already posted. One other thing to keep in mind is that it takes a lot of power to drive those two blowers. So while it might only be making 1000hp on your dyno, there's probably 200-300 hundred (or more?) being spent to drive those two blowers... which all takes fuel to do.
The lean bank thing is odd. Sounds like an air flow/distribution issue to me.
This guy gets it! You are asking ALOT of that carb. That motor is probably making 1300hp or more. You are asking it to flow 1300hp worth of e85. That is like 1700hp worth of gas! And trying to do it with single needle and seat? I bet if you ran that motor WOT for a second or two longer your AFRs would quickly go dead lean as the bowls continued to empty and started to uncover the jets.
@@wingnutks except for the trys without Jets. LOL nothing there to uncover.
@@MuscleCarGarage2022 single needle and seat is only going to allow so much fuel in the bowls... No matter what jet size
And keep up the great work as always
It's easy, the 90 degree inlet, bolted to the carburetor.
It's totally screwing up the airflow, into s mini tornado 🌪.
Screwing up the air bleed vents on top of the fuel bowl.
You need a straight shot of Air.
its been run many times in the past
@@richardholdener1727 But your trying to pull a different fuel now. May not behave the same way
Could be a leaky $0.15 valve seal on one side, admitting just enough oil to throw off your AFR on that bank. Do you have O2 on every cylinder, or just one per bank? Had a similar issue on our 500 HP small block with 1 AFR in each bank, traced a half-point AFR discrepancy to a valve seal Your videos are outstanding - thanks for publishing these. Loved the DZ-302 vs. Boss 302, hydraulic cammed small blocks, de-bunking the "blower cam" myths, de-bunking over-square vs. under-square vs. maximizing displacement. Please keep up the great work.
Hey Richard
Carb hats mixed with well made vent extensions helped many people get a much richer top end fuel mixture. They have hats that direct the air in the front bowls better. This may help in right and left bank equalization.
we ran vent extensions
This video is OLD (like me) and there have been nearly 600 comments left, soooo......I'm not gonna read 'em all to see if you found the prob. BUT......I suspect, as others have said, that your wonky side-to-side and lean high-speed AFR's are/were being caused by turbulence in that 90° hat. I had the same issue several decades ago when turbocharging a carbed 2.3 Ford Lima (Pinto) engine with a homemade hat. I fixed mine by extending the height of the hat (in a Courier mini-truck, so plenty of room) and ~ while leaving the inlet "nipple" to blow into the hat down low ~ I pop-riveted a velocity stack to the choke horn with its' inlet way up at the top of the hat. Soooo........charge air entering the hat hit the side of the velocity stack, traveled up to the top of the hat's "chamber", then made a 180° turn into the top of the velocity stack and entered the carb in a straight shot. VOILA'........my wonky AFR's and high-speed lean condition were fixed!
dyno fuel pump
Dr. Horsepower.. good job on the videos
I believe it might be the kanute valve at the flange restrictor.
I like to keep it simple .I have a holley bowl fitted with a external sight glass / fuel level gauge that I use occasionally .( In one run all the delivery questions answered).
There maybe a harmonic in the intercooler to carb or even the manifold ?
Is the relative humidity high enough to have some icing around the booster venturis during high cfm airflow? Have you tried larger boosters to slow down the air flow through the boosters? The air may be flowing too fast though the boosters to get a stable low pressure area to draw fuel from.
The fuel pump for sure, same happened to me
AF ratio following boost curve, would be interesting to see a test of boost flowing straight down into the carb. That short side curve is disrupting airflow as velocity increases.
Plum the hat 90° to make sure that turbo hat isnt favoring only one side of the carb and creating turbulence on the other. Plus I would run the boost reference up towards the snout where the pressure in more constant maybe with a "L" shaped pickup tube inside facing incoming flow. Maybe throw a couple boost gauges in different spots for comparison and to rule out turbulence or high/low spots around the base of that hat.
Listened to this video now 3 times, fuel pressure is fine, checked before and after the regulator, and this problem is going on with 2 different E85 carbs and a gas carb, the common component is the carb hat, and running 2 superchargers is increasing the CFM dramatically, air is hitting the back of the hat, and not able to flow through the rear throttles, backing up and causing an eddie effect (turbulence) and messing with the front throttles ability to get a smooth flow of air, and likely surging causing the rich lean bouncing we see on the HP curve instead of the smoother curve we usually see. If you can cut the hat and weld a second fitting for each charger, the boosted charge air should stop being so turbulent, I suppose this could also be remedied with a splitter installed that others have suggested as well. Good luck with the diagnosis, great work as usual
we've run this power with this hat before with no problems
@@richardholdener1727 But different fuel now, right?
Venturi tubes(stacks)over the bores, or a restrictor plate, to increase the pressure differential on the float bowls. *More vacuum at that booster venturis. More pressure on the bowl. Modulator rings on a DCOE carb.
monitoring fuel pressure is one thing but is the float bowl level being maintained? Can you look jn the sight glasses on the bowls? If it drops under load at high rpm, it will lean out. The seat could be drilled out. If thats not it, then look to enlarge passages in carb body.
I would try jetting down your primary’s and leave secondary’s where they are and bring up your fuel pressure a couple pounds under boost
What is the BSFC? Once the amount of fuel the engine is consuming has been established, a fuel issue can be verified. An engine with excessive amount of fuel (90 Lb/Hr of flow though 8 injectors making just over 500 Horsepower excessive) can "Trick" the O2 sensors into reading a lean condition.
Once a fueling issue has been identified, start with the incoming air and the signaling for fuel. Several have mentioned that the carburetor hat could disturb airflow in unintended manors. Once verified that the corroborator is receiving the correct signals to deliver the correct amount of fuel, analyze the fuel entry point into the corroborator. Work back through the complete fuel system and sub-system until a point of antiquate fuel has been reached.
I hope this helps you out, or may provide guidance for another in the future.
Thank you and best of luck.
Holley hi ram twin carbs .Revised blower hats with a veined air straighteners if you will .Start tall work your way down in height until condition recurs. The bank that's lean is opposite engine rotation isn't it?
Try mounting the carbs backwards ( front primary fuel bowl to the rear of the engine)in the intake manifold & run the engine. If the side of the engine that is NOW lean is the other bank, then definitely the a/f lean problem is the carburetor or carbs if you test both carbs backward. But if the a/f ratio lean is still on the original bank of the engine, well the problem is instrumentation( as industrial instrumentation ( PLC, inputs, outputs, set points, close-loop, telemetries, etc) system, and I mean the system( wiring harnesses, connectors, modules, boards, chips, processor,etc.), not just the wide band EGO sensors.
I think there are a few people on here that are on the right track. Try straightening up the air flow in to the top of the carb, run the vent extension to the mouth of the carb hat with slightly larger inlets, and I couldn't tell if the carbs that were ran had down leg booster. But it might help to move the vacuum signal closer to the area where there is maximum air velocity through the venture's of the card. I couldn't tell but it looked like the booster were straight.
Have you tried vent tube extensions that bend into the air stream inside the hat? It acts as a pito tube and will give you more fuel flow at higher boost by increasing the pressure in the bowls. It work really well. Playing with the length and where they are in the hat makes a big differance.
we did have those
Maybe it’s the dynamics of flow through carb hat to carb into manifold where the mixture is localized to the side that’s not lean
Shorter bowl vents, bonnet extension and an Extreme Velocity bonnet should sort out the lean top end fuel distribution providing its not an intake manifold issue, can also try boosting the voltage on the fuel pump to see if that will help....
Sorry I'm no help, I stopped doing the carburetor thing many years now, and back then it was all naturally aspirated stuff, anyway I feel your frustration and you got me on the edge of the seat!😳
If there are no vacuum leaks in the system, are the fuel bowls holding enough fuel when making the high rpm pull? Bowl extensions, high flow needle and seats, larger fuel lines from the regulator(s)? Try a belt or cam driven fuel pump with bypass back to the tank. Mechanical fuel pumps are flow tested at 100psi which is approximately 8000 rpm!
Great vids. With an Ls, what spring pressure is it necessary to do a rocker trunnion upgrade?
I'd say it's a combination of dirty air from running twin blowers. The flow is clashing in the pipe and causing a massive spiraling effect. Try splitting the intake all the way to the carb hat, one entry on each half. I'm sure you'd see what was going on if there was a see thru plate over the top.
Have you done a video on injection timing and how its effects on efficiency and power for a gen 3/4 ls with a cam that has a lot of overlap?
What are the spark plug showing? Is it so rich that it is reading lean? Been there, done that! Pull the plugs, I would bet they are fueled to the max. For sure if it's too rich, there is unburned oxygen in the exhaust pipes showing lean. That's what I would try first. Next up would be looking at possibly adding vent tube extensions to see what that does. If that does not do it, I would maybe think the bowls are being not filled by the pump, or it may need the dual needle and seat bowls. But with two blowers, if it is making 1000 at the crank, can you imagine what both of the blowers are pulling for power. I bet the bsfc is very high! My 2 cents anyway!
not rich
I'd look into your carb hat and vent tubes. That looks like a very gnarly, short radius bend plus you want your vent tubes pointed into the air steam. Often guys build tube extentions that extend a short ways pass the carb hat.
Have you flow tested the pump and checked the filter? So pressure is staying at 8 through the whole run? If so, that doesn't make sense. What do the plugs say? Any super lean cylinders on that one side?
I'd say maybe the 15PSI air in the bowl causes the float to lift, but I imagine you guys have run that with 15 PSI of boost or more. Maybe it's lifting just enough to make a difference when you're trying make such large numbers. Denser air might require a slightly weighted float, or at least an adjusted float level.
He already mentioned it was a fuel pump supply problem
This may have been suggested but I'll put it out there in case this issue hasnt been resolved. Could this be a pressure differential issue from above and below the carb?
Have you ever played with the oldschool turbo sbc where the carb was before the impeller?
Is the header leaking on the side that is lean? Could have a gasket just starting to leak and sucking air in... had this happen on a brand new car, everything looked fine changed lots of parts before finding it.
Will a blown intake gasket effect the fuel distribution with a blow through carb? Just a thought. The issue probably bowl vent extensions not right. However I'm sure you guy's know about them and have already payed around with vent extensions. Just failed to mention it.
Are the plugs on the reported lean side reading lean?? Just an idea sometimes it can be instrumentation. Also i forgot if you said it or not, are you running boost reference power valves??
I’d suggest starting the engine and using a fine mist of carb cleaner around the intake to make sure there are no vacuum leaks.
I'm pretty new to all of this stuff but, could there be a chance that the 2 chargers are creating so much pressure in the intake as to push back ( backpressure) so much on the carb to as to hinder it's flow? I mean it actually is forcing air back into the carb. I haven't read or maybe have missed it but did you change to a completely different intake?
Eric the car guy had an issue like this. It was the carb air inlet pipe (idk if that's its name). It was literally pulling the fuel out of the carb, I stead of pushing it into the engine. Not sure if this is the same thing but it may be something to look at.
is the boost air flow maybe being forced down the "lean" side of the engine/intake more than the other side?
Volume of the fuel pump with should suffice for all the other tests I've seen you run on the dyno but that's one thing I would check volume from the fuel pump espresso will be fine but volume won't be there secondly atomization of the fuel even though the air pressure going through the fuel carburetors on atomized fuel as well so you could get puddling in the manifold there for not allowing enough atomization of the fuel to reach the cylinder try placing more spacers in between the carburetor and the top side of the manifold and see if the air fuel ratio changes enough that it comes back into you're 12 to 10 ratio on on Gad
Run one supercharger, and see if you can get a handle on the A/F. If you can control one. Hook both back up and measure the pressure in the bonnet. You may be to a point of top pressure to need a duel needle and seat.
I run a .152" seat in my E85 Qjets, no way its going to keep up with boost on E85. Not happening. Dual needle seats are the way most of us are going with high boost and E85 on Holley style carbs, a single can't hang. Then you have boosters that need to be larger, usually around .140"-.145" for NA. The Quick Fuel carbs are ok, but not perfect and not optimized, they can take some more work. If you want to run E85 Holleys blow through or not, the guy to talk to is Mark Sullens. I'll share this video with him for you.
Was this engine leaning out due to it being a single carburetor like you mentioned before? I’m randomly scouring the internet trying to think of a ram-charging setup. Thinking about going to the junkyard for an explorer 5.0 and doing a brawler carb like you suggested
Have you checked the plugs? One o2 per bank is going to read the average of those cylinders. Nothing fell down into an intake runner and blocking it, is it? Sounds crazy but I’ve seen it. Otherwise possible vacuum leak on that side.
I use to have a fuel problem also until I switch to a bigger boost activated power that had a higher flow capability and bigger ventures holes drilled
Have someone or a camera in the dyno room when doing a pull and set the float bowl level at center of the sight plug make sure the float blow levels stay at center during the pull that will rule out a fuel delivery issue. Lean on one side sound like a intake gasket leak under boost that may not show under vacuum. It's always nice to vent the fuel bowls outside of the intake bonnet because even with a boost regulator you can never exceed the pumps free flow pressure rate with the combined regulated pressure and boost pressure.(example if you pump flows 20 psi free flow and flows say 30 psi before a regulator set at say 7psi you would think you could do 23psi boost 7+23=30 you can't. The combined boost and regulated psi can not exceed free flow. So if free flow was 20psi and you set the regulator to 7psi you can only run 13psi max) I understand were people are going with the 90 degree bonnet but we have a procharged dragster making 1400+ with the same bonnet.
Ricky Rocks I think he needs to run bigger bowels. He’s just running out of fuel.
we measured pressure before and after reg
@@richardholdener1727 verify for fuel in the bowls, please.
Do you think it has something to with air flow like the tube on the carb or the intake maybe a different intake manifold I know nothing about those carbs but are they rated for that boost it seems like if it's all under boost it might not flow that extra fuel but surely they would have something for that since that's what they are for
Have u thought about running a dual carb set up to double you fuel flow?
Did you change for exhaust leaks at the exhaust manifolds flanges it cracks in the tubes bringing fresh air into the exhaust?
Have you checked flow from the pump at different reference pressures to see what the actual G/LPH are? Is there a size difference between the venturi horns or a dimension difference not dealing well with the increase in air flow. Last is it possible you're blowing air past the seals?
I agree with a bunch of comments-if the carbs worked on other setups they’re probably not the problem. Look at fuel pressure at the carb inlet, is it making it all the way there? As mentioned, look for vacuum leaks for the side-side problem. I also don’t like the looks of that carb hat, but if it’s worked before... Can you measure fuel flow between regulator and carb float bowls? Verify the gross fuel flow relative to lbs/min of air? How about a restriction in the fuel hoses after the regulator (damage)? Very weird problem.
Get the new Holley ECU! Good luck and keep em comin!
how is the boost reference rising? might need a different (higher) ratio?
Younger person hear, don't get me wrong rebuilt my fair share of carbs, your problem is your running carb instead of efi.love your stuff. Been reading for many many years
Make sure the boosters are drilled. I didn't hear you address that. Have you tried plugging the high speed bleeds? How about the fuel log, is it big or do you have 2 lines to the carb from the regulator? Are the floats travelling freely? Did you drill the PVCRs?
I just went through a heck of a dyno session with a 351c and a torqstorm. It was two days long and watched this video trying to get help. What we found was my car was built correctly by me. There were two issues that killed it. First it was lean... We found that putting some nylon tubing on the vent tubes and pointing them into the charge tube fixed the lean condition. Then it went pig rich. Many pulls and the smallest jets we could find didn't fix it. 10:1 are. The intake side of the supercharger was sucking the rubber hose shut. Hope this helps someone. 667 hp and 590tq. Runs awesome... What was your resolution?
I'm only part-way thru this but did you boost reference the power valve? It entails plugging one passage and opening up another. Oops! I'm further along and see that you did. Must be the shop cloth that accidentally got into on side on the intake! LOL....just kidding!
Your testing has narrowed it to two possibilities. Fuel supply or ignition. The known good CSU carb on gas is going lean up top, so problem is elsewhere. Fire up the parts cannon. I would guess the Holley Ecu is borked even just firing the coils.
I'm not any expert, as I say I'm always a novice that's always learning, but if one bank is good, the other cylinder bank is leaner would it be a warped intake or cylinder head on that bank being able to suck in more air around the leaking gasket causing it to lean out that one side?
i agree that the hat is causing a turbulence issue with the air flow. a quick fix could be to make a divider plate to stick inside the hat so it separates the air to each bank before it hits the turbulent section and possibly one down under the carb. if the one under the carb makes the most difference then the intake design is the issue and won't work well with this combo. a performer rpm air gap might work better if they make something like that for the LS. another thought was what would happen with a dual 4 setup i don't think it will solve the side to side issue but it is something you didn't try. might change the air fuel delivery in a good way?
Being boost sensitive, the regulator might not be getting sufficient signal.
Measure boost pressures close to carb (like you have it) and check also near the blower(s), I think you might see a higher pressure reading, at the carburetor you are going to higher velocity because of the moving air but less boost, all the backed up air (boost) is going to be at the blower.
Just a suggestion from an observation.
- Make sure you dont have a exaust leek that would affect your o2 readingd
- try getting a boost reference from a different location. You could be getting a fals reading if the location you are getting you refference from is a low pressure zone like the inside radious of a tight curve.
- Make sure your boost pressure reference at the regulator is equal to the true boost pressure,
- make sure you dont have a bad regulator
- make sure you regulator can supply the fuel demands ( try a different brand of regulator)
Something is going on inside the intake. One bank consistently leaner, maybe the air being forced into the carb (twin chargers, lots of flow) is loading up in the hat and causing swirl/tumble/flow issues as it’s forced through the carb. Try clicking the hat to see if the distribution changes. Point the hat at the back of the engine (more plumbing😂😂) and see if the left bank consistently goes lean.
I found on my combo that the quick fuel I had 1030 hp was the limit before a/f went uncomfortably lean at the top my CSU twin seat cured the problem immediately, when talking to Kevin he said he revised his thinking and said 1200 hp was the limit of single needle and seat down from 1400 on his website. It would be interesting if someone had one to try otherwise maybe the fuel pump is not providing the fuel anymore for some unknown reason like are there vanes in it petering out or maybe voltage drop of pump that creeped in , have you checked the filter ?
I don’t know much about carbs, but various a/f reading between banks usually isn’t going to be the carb I wouldn’t think, possible missfire causing the a/f to read lean, unburned oxygen. Turbo John has a couple good videos on blow through setups since he did it forever before going to fuel injection. One thing I did learn from watching his videos is the vent tubes and how it’s positioning is in the hat.
Did you block off the vacuum port when using the boost reference power valves
Extend the vent tubes into the pipe supplying the hat with boost. I made my own blow through and it worked well
did that