WHAT'S INSIDE? -BLOW THROUGH CARBS

[@manitoublack]

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: kzbin.info/www/bejne/hJLNZH-CYt98oJI @ 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 ;).

[@manitoublack]

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

[@carlitosgy6]

You can be totally right

[@Davefromwisconsin]

Yup I thought about Eric’s dilemma right away. Richard, Change the air hat.

[@fattsthebavarian6104]

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.

[@watsisbuttndo829]

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.

[@superkillr]

To anyone who can't find the answer.... it was the dyno fuel pump.

[@smblock400006]

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.

[@finnroen2334]

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.

[@Rdawg33]

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

[@henrysmith8012]

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.

[@pistoninthewind]

I just saw this vid and thought exactly the same thing.

[@HeadFlowInc]

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.

[@minibuggies926]

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!

[@richardholdener1727]

We've run the carb and hat successfully many times

[@Turbo_Todd]

@@richardholdener1727 But the fuel is different. Wouldn't that make a difference?

[@kathleenhastie6967]

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.

[@goodmanboattransport3441]

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

[@richardholdener1727]

we've run this power with this hat before with no problems

[@Turbo_Todd]

@@richardholdener1727 But different fuel now, right?

[@koalafiedengineering1200]

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......

[@tylermurray4583]

Check intake for vacuum leak or any other vacuum leak we ran into the same exact issue on our blow through 406

[@addmoreboostOG]

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.

[@Craigy82]

Can you build a bigger plenum on top of the carb? Or straighten the air out coming into the carb?

[@josmith213]

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

[@ssoffshore5111]

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.

[@wingnutks]

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.

[@MuscleCarGarage2022]

@@wingnutks except for the trys without Jets. LOL nothing there to uncover.

[@wingnutks]

@@MuscleCarGarage2022 single needle and seat is only going to allow so much fuel in the bowls... No matter what jet size

[@stevenlegere4193]

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.

[@kathysarmcandy1992]

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.

[@kylemilligan752]

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.

[@dennykatz157]

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!

[@MRMOPARMAN0426]

Have you checked the fuel pressure post reg? Can you put a pressure guage in the bowl and make sure it matches boost pressure coming into the carb?

[@stevenhill719]

That would be cool data to review. Hat boost vs bowl boost. A deviation there is directly relative to effective fuel pressure. Good comment.

[@standbackperformance]

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.

[@JeffreyGatrell-jp3mf]

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.

[@richardholdener1727]

we did have those

[@scottallpress3818]

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 ??

[@timothywilkinson7749]

because u have one lean side and one good u could have a leek at the intake to head side blowing vacuum/ boost out will give u a lean conduction would also explain y it gets worse with rpm/boost

[@timothywilkinson7749]

i would definitely b looking toward the one side lean could b a value float or seal problem or even a not so sealed head. a cylinder to cylinder afr would b able to spot the problem area more exact. could b to much spark on one cylinder causing erratic combustion cause a lean. to much plug gape or to much dwell time. witch could b bad ignition control or rarely a bad coil. but most likely is a vacuum leak on the intake crake or a bad gasket.

[@dhatchett6030]

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

[@jessemagruder]

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.

[@richardholdener1727]

we did run extensions as indicted in the video

[@nhraracer973]

That would help with the boost charge for sure

[@nhraracer973]

Vent tubes for sure

[@snaproll94e]

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.

[@Sleeperdude]

I would try bowl vent extensions and point them into the path of the incoming air that should richen it up usually

[@randalltufts3321]

#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.

[@richardholdener1727]

DYNO FUEL PUMP

[@garygroves5893]

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.

[@richardholdener1727]

we ran vent extensions

[@pablojanski.2559]

One thing I have seen happen with e85 is fuel foaming.. e85 seems to be more susceptible to fuel foaming.. as fuel pressure rises with boost and the float level is dropping due to fuel consumption it foams worse and worse.. like a garden hose in a bucket, Low pressure high volume, no foam.. high pressure , less volume but more foaming.. Also, are the plugs actually verifying the elan condition? some time e85 can show a false lean due to too much fuel and the 02 is picking up the un burned oxygen.

[@omarbengochea7271]

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.

[@billythebake]

Bigger jets, drilled PVCR passages, jets, removed jets, big needle/seats, plugged bleeds, swapped carbs... sounds like you've picked most of the low-hanging fruit, Richard. Got enough fuel pressure to overcome the boost? Checked the pressure AT the carb inlet? Tried those clear sight plugs @ the bowls to see if the bowls are full @ load? Since TWO carbs have the same results, it makes me wonder if 2 carbs had the same problem, or if the problem is systemic Maybe put the carb on backwards and see if the problem switches banks... Edit: exhaust restricted on one side? Maybe worth spending a few minutes looking there looking?

[@goofymama8637]

I think it’s the fact that they’re trying to flow that much fuel through a single needle and seat. There is a reason why after about 900 hp most people step up to dual needle and seats for e85

[@jerrychaney7100]

I have a setup recommendation that might work better. Use a tunnel ram intake with dual carbs and run individual intercoolers for the blowers

[@L_S73]

Thx. For all the great info. And videos. Keep up the great work. Love your videos

[@BULLDOGHOTSHOT1]

I'm not sure if you mentioned the size of the carb... Maybe the cfm was too large... With ethanol or meth you usually need a smaller cfm carb to allow a higher boost pressure on top vs the bottom so the float bowls with have a higher pressure to force fuel through the carb into the air stream... Usually 5 lbs less on bottom vs top is usually good enough restriction.

[@blakeperritt9016]

Great video Richard! These are getting more and more interesting

[@terrencehall7264]

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.

[@raycasner]

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!

[@richardholdener1727]

dyno fuel pump

[@1fast72nova]

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?

[@MastersOfMask]

I would like to see a Holley X intake manifold with the twin Torqstorms SCs.

[@raymondleathers5921]

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.

[@joshuamelton8908]

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.

[@peterlyons4389]

Did you try turning the top hat on the carb to change where the leen cylinders might change to.

[@richardholdener1727]

IT WAS THE DYNO FUEL PUMP

[@ThePunisher-sg1jg]

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?

[@spencersandell1498]

Something going on with the boosters or venturis? Could It be losing "signal" some how the area of low pressure not pulling hard enough.

[@timothybayliss6680]

It's one carb that's flowing a ton of fuel. There is a chance that it has a gas carb body and the booster transfer circuit is not sized big enough. If you take out the jets and plug the air bleeds it should be so rich it misfires. There is something everyone isn't seeing here.

[@dustinfrey3067]

The intake seems to have a vacuum leak. The is more than likely why your AFRs are off on one side. Even though is boosted just like exhaust will scavenge when You have high flow volume and it will suck air, again even under boost pressure.

[@ts302]

Hey Dustin, the one thing I've learned from Richard's channel is to treat a boosted engine like it's NA. Check for any vacuum (boost?) leaks between carb to manifold and intake to heads. I would even do a cylinder compression check. Again eliminate the small issues before the deep dive into the problem.

[@dustinfrey3067]

@@ts302 Well there is this idea that a boosted engine won't have a vacuum leak and therefore run lean. People think since there is boost pressure in the manifold that you will have a boost leak instead of a vacuum leak. But that just isn't accurate when you start using large volumes of air at a high velocity. The velocity of the air across the leak will actually scavenge and pull air in like a vacuum leak. So at idle you may not have a small boost leak since you have both blowers turning, or it may neutralize the effects of a vacuum leak. You may not even be able to use the brake clean/carb cleaner trick to find it. We have to remember, there are only so many things that can cause a lean issue. Not enough fuel from carb or efi system, or unmetered/ additional air entering the system that the fuel system cannot account for. A vacuum leak would explain the side to side afrs and the issue to get worse higher into the rpm range, higher air volume at a higher velocity will scavenge more air.

[@ts302]

@@dustinfrey3067 the clues that jump out for me is the side to side AF ratios and the fact that removing the carb spacer helped a little (If I heard correctly Richard stated a couple of points). With all due respect to Richard, his 'this hat/carb worked before/ been there done that' attitude would not fly in our maintenance shop! As an electrician, when all else fails, start over from the beginning and check the basics, leave no stone unturned. It's a lean condition, either too much air or not enough fuel-why? As keyboard technicians we can only suggest (he asked,LOL) and wait-it's Richard and crew that will ultimately find the fix.

[@TurboJohnRacing]

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!

[@richardholdener1727]

not rich

[@dbr5740]

My brother and I have experienced this same thing in our dragster we went to the dyno 3 times think weve found something and trying it again whwn we eventually got ro the point we tore the engine all the way down we found multiple broken valve springs. When we were at the dyno we did compressions tests and new plugs new distributor caps, rotors. But it ended up being valve springs.

[@richardholdener1727]

we checked springs

[@jacobstair7487]

if you took the main jets out and it still leaned out at the top end, then the boosters may be to small or the port to the booster,

[@timothybayliss6680]

They removed the jets and plugged the air bleeds. I was thinking it was booster transfer circuit as well. There is a restriction somewhere.

[@kelevra558]

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??

[@dougbawden4321]

Extend the vent tubes into the pipe supplying the hat with boost. I made my own blow through and it worked well

[@richardholdener1727]

did that

[@ds4284]

I agree with manitoublack. I'm an airline rated pilot and an aircraft mechanic. The airflow in the hat is the likely issue. Have you tried "aiming" the hat from different directions? I'm assuming that's a practical solution. Quite a bit of time and headscratching has been done on one of my projects with this issue and I've not even had it running yet! It's a GM LN2 2.2 liter 4 cyl OHV that I've raised the intake ports about 3/4". Expected power will hopefully be 225 hp.

[@richardholdener1727]

we've run this hat and carb together my times

[@nono-fn3zc]

Are you screwing up the Venturi effect with the boost? Maybe vent tube extensions? Jet extensions? Something to get that fuel sucked up better from the bowl.

[@codynelson3493]

Hey Richard what was the issue? I'm also doing a blow through A3000 deal with methanol.

[@richardholdener1727]

feed pump

[@jessehasch8493]

If its impossible to get enough gas with one carburetor, just switch to a tunnel ram, and run TWO blow through carbs. Convert it to twin intercoolers, and have each supercharger feed one carb. Give it 2 carbs worth of gas, and youll only need one fuel pump. By the way if a carbs power valve was removed, its for a reason lol. Usually theyre deleted in the rear for drag racers because they favor drivability and not all out power.

[@triggerwarning2439]

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.

[@davidjohnson468]

I believe it might be the kanute valve at the flange restrictor.

[@joegrosso6687]

A lot of attention to the intake side. You pulled the Jets and still not enough fuel at upper rpm. Have you played with exhaust?? The other side of the equation. If the exhaust is to efficient at the higher rpm it could be scavenging fuel out of the cylinders. A restriction of some type could give you a direction or additional info. Just my thoughts, look forward to follow in this project.

[@glareofspace]

is the boost air flow maybe being forced down the "lean" side of the engine/intake more than the other side?

[@dirtrider2833]

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

[@jlaudio11]

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.

[@pro1342]

Have you pulled the plugs for a reading? It's possible one cylinder is not firing correctly, leading to a false reading on the O2. It could be a bad spark plug or coil giving out. I think Matt Happle had a similar problem on 8F8 where a bad coil was leading to a lot of carnage. Could also be valve train related. Possibly a lifter collapsing at higher rpm, or that it's pumping up and hanging a valve open? Swapping everything side to side could narrow it down quickly.

[@roberttomich1279]

- 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)

[@WesternReloader]

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

[@bendunbar5933]

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?

[@Patricks_Projects]

Set a boostreference pickup further up in the chargetube, with a pitot tube facing the airflow. For both floatbowl and pressureregulator.

[@JoakimRoeed]

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😁

[@supercoupe28]

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.

[@wyattwunderlin4445]

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.

[@brianlewis5663]

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?

[@rickyrocks5946]

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.

[@bryanworthington5228]

Ricky Rocks I think he needs to run bigger bowels. He’s just running out of fuel.

[@richardholdener1727]

we measured pressure before and after reg

[@ts302]

@@richardholdener1727 verify for fuel in the bowls, please.

[@munro3274]

Sounds like boost pressure down the vent tubes. Try extending the vent tubes into hat by 6 to 8” I’ve seen that work before. Best of luck

[@CrOmeBlueM1]

Yeah, I was going to say 12" tubes through the hat in a situation like this 6" is probably too short for the weak signal.

[@young11984]

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....

[@westernperf]

I couldn't tell, is the regulator a return style, after the fuel log so you're getting all the fuel volume to the carb and only returning what isn't used, like an efi system? This is what we do on the larger alky carb systems to maintain fuel volume.Also you have twice the parasitic loss from 2 superchargers. I don't know how much drag they represent, but let's say one is 200hp. Two would be 400hp. So if you're trying to make 1000hp you need enough fuel to supply 1400hp.

[@prestonedmonds4128]

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?

[@spiroskatsikas]

Richard there something I want to ask the manifold is restrictive and maybe the flow is not good enough to meter the fuel flow across the venture maybe

[@TractorWrangler01]

Is the fuel volume restricted somewhere? Pressure up volumn down? Is the air coming in backing up the fuel? Is the hat making a vortex of air in an inapproprite place as boost moves up? I'm just guessing of course. How about a big spacer to see of it behaves differently? A geometry change in the airflow pattern? Put the fuel inlet in a low pressure area created by the the flow of air?

[@Screamn03]

Like others have stated the Carb hat seems suspect. Also, I didn’t hear it mentioned but worth saying, just because you’ve made 1000+ before doesn’t mean it’s the same here. You’re driving two blowers so BSFC is going to be higher. Then you throw e85 on top of that fuel volume is huge. Is it possible to flow enough fuel through the carb that it can become turbulent and airate?

[@richardholdener1727]

we ran the test on gas also-same results

[@michaelrogers9779]

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.

[@damianellis3554]

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

[@Marc_Wolfe]

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.

[@delberttaylor1479]

He already mentioned it was a fuel pump supply problem

[@jwillettgn]

Carb icing up at the higher rpm/flow? Fooling around with a 460 Ford and gasohol 40 years ago the engine would cut off at high rpm’s, we would roll to a stop. After about 30 seconds it would start right up again and off we would go. Found it by jumping out and looking down the carb really fast and finally saw it iced up but melting really fast. Went back to straight gas and no problems. It’s a shot in the dark but who knows. Try it with the intercooler water off to see what happens.

[@richardholdener1727]

we tried fuel too

[@nellyfarnsworth7381]

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.

[@richardholdener1727]

its been run many times in the past

[@Turbo_Todd]

@@richardholdener1727 But your trying to pull a different fuel now. May not behave the same way

[@Rubberweasel]

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?

[@fattsthebavarian6104]

Maybe look at high speed air bleeds and emulsion hole number, size, and location

[@richardholdener1727]

we did

[@spiroskatsikas]

Ok so the one bank is leaner the flow into the manifold, is that 4 barrel carburetor open only two ventures open at a time so are u opening the thottle 100% or are u using ONLY one side of cab in a duel plane crank ,sorry im not into v8 engine ,i have only experience on fours boosted and n/a like lotus twin cams sr20 and alike

[@Marc_Wolfe]

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.

[@db8886]

Sounds like the fuel side might not be the problem. It almost sounds like an integrity issue. No matter what you try fuel wise you get the same basic outcome,... you mentioned that one bank was ok and one bank was acting wierd/lean. You said you ran a compression check, but did you run a leak down test? (A leak down tester uses a set of gauges and shop air to check for different engine issues or to see how well an engines condition is. Or to keep tabs on internal wear for race use. Did you leak down test the good bank of cylinders for a control then leak down test the lean bank of cylinders to see if there is an oddity between the banks? You can test each cylinder at top dead center ( both valves closed) by turning the engine over by hand which will put the cam in play incase there are issues stemming from the valve train you might have missed, or you could undo all the rockers to seat all the valves and then you could just cut to the chase and hit all the cylinders one after the other without all the turning over of the engine. Wouldn't hurt to also undo the rockers so all valves are seated, make a top block off plate for the intake where the carb sits, put a tapped hole in that plate to accept the leak down tester fitting and leak down test the whole intake and heads up to the back of the intake valves. All this would show you if there is a crack that just showed up somewhere, a bad intake seal or head seal, if the valves are leaking at the seats (check by pressurising a cylinder and check valves dry then with light oil like marvel oil dripped on the closed seat surface in the intake runner, look for bubbles) (ive seen leaking valve to seat issues cause mid to top end tune problems).....

[@richardholdener1727]

we know what leak down tester is-motor makes correct power na

[@remybrouwer8700]

Richard, I do NA Engines never had done a boosted engine, but have you tried the carburetor that worked before like you said as well with double source of boost before or just a single source ? You mention it goes lean, but at what rpm is that happening and at what boost level ? That was not clear to me, did you try a double carburetor setup ? And each carburetor been feed with its single supercharger ? The other thing is that carburetors cool down the mix so if you install two carburetors you may not need the intercooler I will prefer in a carburetor setup actually to cool the fuel with coolers that use ice water to increase that effect, other thing is that you are using a open plenum manifold I will suggest that you put back the 4 hole spacer 1" + plus higher to make the other bank of cylinders come a little to life.

[@michaelcastorino5184]

Is it possible that under high boost the air pressure in the body of the carburetor is higher than the fuel pressure trying to make its way in. It could be a physics issue more than anything mechanical. Almost like boost pressure trying to get into the coolant system.

[@spiroskatsikas]

Well if u leaning out ,the fuel doesn't mean the fuel bowl is empty, it can only be one of two things ,one fuel correction jet is to small or two the fuel pressure is dropping below the boost pressure and the blow throw hat must be facing forward and not to the sides where exhaust come out ,it should face flywheel or front pulleys to flow even mixtures through out .

[@spiroskatsikas]

So do we have a answer because I will bet I'm right, arrogant little me

[@spiroskatsikas]

The only other thing i can think to do is fill the bowls with fuel pressure same and run it n/a then if all good add boost but just 2psi then stop, and open the fuel bowl it should be full if it isn't well u know, and remove the port in the hat to the inlet manifold runner number one ,the hat is 3inch wide and the port is a little better because of crosssectional area is smaller and same psi because of 50mm/60mm port is less pound's per square inch, Richard talk to me

[@jamiemorgan4943]

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?

[@Sonos45]

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.

[@st8jkt69]

Annular boosters all good? Maybe it's drawing more on 1 side

[@finnroen2334]

We usually start by checking fuel flow out of the FPR when pressurizing it to the same level as maksimum boost pressure. 1000 hp is at least 100 lb/min airflow, right? Running E85 at lambda 0.8 true AFR is 7.84:1 and 100 lb/min airflow / 7.84 = 12.8 lb/min fuelflow. We mulitply by 60 to get lb/hr and get to 765 lb/hr as required fuelflow, right? To avoid ANY fuel pressure loss, out test have shown us that one NEEDS 40% higher fuelflowcapasity then the carburetor (or fuel injectors can move) so this results in 1072 lb/hr out for the return of the FPR. We mulitply by 10.5 to get ccm = 11250ccm/min which is 11,25 L pr. min. or 2.97 gallons pr. min. When tested with the fuelpump running and having air pressure equal to boost pressure into the FPR, you should fill a gallon jug with the fuelflow from the return hose from the FPR in just 20 sec! Using more time than 20 sec. pr. gallon tells us fuelflow is inadequate for 1000 hp on E85 and you will get fuel pressure loss, fuel level loss and therefor problems with higher AFR. With this kind of fuelflow I would plumb the carburetor like a fuel injector, feeding the carburetor fuel directly from the hose / pipe coming from the fuelpump and going to the FPR.

[@BULLDOGHOTSHOT1]

Uhhhhh belt slip on one of the blowers and it's making a circulation of air from one blower to the other?

[@billythebake]

Both blowers push into the intercooler... *guessing* that they wouldn't be able to cause the leanout

[@Smokermouse]

Are you sure the lean side head gasket is not on upside down.

[@diesel-technology5507]

Well 1200 on gas and 1200 on e85 need much different afr as far as I recall....so surely 1200 gas would equate to 1000 e85 based on their differing stoichiometric values. So I think you are right in the fuel requirements not being met, but I think it's simply the carburettor being at its maximum capacity than anything else

[@thegrumpyoldmillennial328]

Could it be a turbulence issue in the manifold? Possibly ornery single plane tendencies?

[@orionsmith7669]

1000+hp on E85 usually means dual needle and seat bowls. What’s good for 1200 on gas doesn’t equal nearly the same fuel flow on E85. Let’s say for example that single needle and seat was maxed at 1200hp on gasoline. That means on E85 you could expect it to be out of flow around 850ish HP. Assuming the standard 30% more fuel flow requirements.

[@richardholdener1727]

THNX-IT WAS A FUEL PUMP SUPPLY PROBLEM

[@ronaldlockhart8657]

Try extending the bole vents up into the hat further and putting them towards the air coming into the hat

[@richardholdener1727]

we did