Car bogs in the corners, road race.

[wmhjr]

Originally Posted by Rokker

I agree with you, but I would think that it would be ok in the straights if it is just fuel slush. Mine keeps bogging until I let go of the throttle for 5-10 seconds.

My theory is that I´m using up fuel on the straights, in the turns the bowls are very low, causing fuel to slush away from the jet´s and therefore the bog appears to be in the turns, But in reality it is just low on fuel.

Btw thi happened with fuel bowls real low and full over the glass. Same symptoms...

Can you post a summit link to the race style float ?
What does that float actually do compared to stock ?

And jet extentions, I don´t see the reason for running them if not dragracing? As lateral g will make the fuel go to the side of the bowl, I don´t see how moving the pickup of the jets back and forth would help ? Not saying, just asking..

I can't at all agree with your conclusions. Here's why.

If you were simply "using up all the fuel on the straights" then even in the straights, at some point you'd lose fuel and the problem would start. I believe it is statistically so improbable that you would end up running the bowls out JUST at the time that you enter a turn (even when the straights are of different lengths) that it's frankly impossible for me to consider. Add in your initial comment about it happening when you "do donuts" and that IMHO totally disproves the theory that long straights are simply consuming your fuel.

If you're using stock lines (meaning probably 3/8 at BEST with multiple restrictions) and a stock pickup, and you're running a strong 502 at 600hp, you're in bad shape. That's way insufficient for that combo.

It's still just a guess, but with such a restrictive fuel system for that combo you could be starving the bowls all the time when you're on the motor. You can't see the sight glass when you're in the car and pushing it. Could be that when you're under load, no matter what the floats are set to the small line and weak pump/location can't supply enough fuel, causing low bowls, then causing starvation at lateral loads.

At that power level, I would replace your fuel line with 1/2"/-8AN, replace your sending unit with one from RobbMC which can handle -8AN, make sure you have dual 3/8" supply at a minimum to the carbs, install an Aeromotive 13205 deadhead regulator (if you don't have a regulator) and either put a RobbMC 1043 pump or a rear mounted better electric pump. For non-FI applications, I'm personally fond of RobbMC mechanical pumps, but that's a personal preference. Once you've done that you know that short of a sumped tank, your fuel delivery to the carb is rock solid and then it's just air bleeds, jets, and float adjustments.

[wmhjr]

BTW, I should clarify something. I'm running at the 600hp level with a built 462, and have run both a custom built 4150HP based 900cfm and currently a Pro-Systems Pro-Series 1000cfm built on a 4150HP base. I'm running 1/2" fuel supply, the 13205 regulator with a bleed orifice using 1/4" vent to the tank and the Poncho version of the RobbMC mechanical pump connected to a stock unsumped tank using the RobbMC A-body sending unit/pickup with 2 -8AN ports.

I can run the car down the straights at 6000rpm regardless of distance, and throw the car into hard bends, pretty much anything I want to do. Neither my fuel pressure nor my engine cares in the least. When the pedal goes down, the rpms go up. Period.

I think it's really important to sort out obvious inadequacies in fuel delivery before trying to troubleshoot performance issues by messing with different floats and/or jets.

[ccracin]

Originally Posted by wmhjr

If you were simply "using up all the fuel on the straights" then even in the straights, at some point you'd lose fuel and the problem would start. I believe it is statistically so improbable that you would end up running the bowls out JUST at the time that you enter a turn (even when the straights are of different lengths) that it's frankly impossible for me to consider. Add in your initial comment about it happening when you "do donuts" and that IMHO totally disproves the theory that long straights are simply consuming your fuel.

If you're using stock lines (meaning probably 3/8 at BEST with multiple restrictions) and a stock pickup, and you're running a strong 502 at 600hp, you're in bad shape. That's way insufficient for that combo.

It's still just a guess, but with such a restrictive fuel system for that combo you could be starving the bowls all the time when you're on the motor. You can't see the sight glass when you're in the car and pushing it. Could be that when you're under load, no matter what the floats are set to the small line and weak pump/location can't supply enough fuel, causing low bowls, then causing starvation at lateral loads.

At that power level, I would replace your fuel line with 1/2"/-8AN, replace your sending unit with one from RobbMC which can handle -8AN, make sure you have dual 3/8" supply at a minimum to the carbs, install an Aeromotive 13205 deadhead regulator (if you don't have a regulator) and either put a RobbMC 1043 pump or a rear mounted better electric pump. For non-FI applications, I'm personally fond of RobbMC mechanical pumps, but that's a personal preference. Once you've done that you know that short of a sumped tank, your fuel delivery to the carb is rock solid and then it's just air bleeds, jets, and float adjustments.

BTW, I should clarify something. I'm running at the 600hp level with a built 462, and have run both a custom built 4150HP based 900cfm and currently a Pro-Systems Pro-Series 1000cfm built on a 4150HP base. I'm running 1/2" fuel supply, the 13205 regulator with a bleed orifice using 1/4" vent to the tank and the Poncho version of the RobbMC mechanical pump connected to a stock unsumped tank using the RobbMC A-body sending unit/pickup with 2 -8AN ports.

I can run the car down the straights at 6000rpm regardless of distance, and throw the car into hard bends, pretty much anything I want to do. Neither my fuel pressure nor my engine cares in the least. When the pedal goes down, the rpms go up. Period.

I think it's really important to sort out obvious inadequacies in fuel delivery before trying to troubleshoot performance issues by messing with different floats and/or jets.

Pay attention to what was written here. Addressing these issues will make your life much simpler. I promise! Good luck!

[mike343sharpstk]

At 600 HP and a 3/8 line… That’s likely the problem. I just re-read original post more closely (Sory!), “Stock fuel tank and Lines”, so yeah, that’s the likely culprit.
For me, the car runs perfectly all the time, except when cornering hard. I’m making maybe 250 HP on a good day, so I am certain the issue is the carb, and it’s an old carter. It’s likely that just screwing the Holley to the car and getting it set up properly may fix my issue, However, the float is a $34 dollar part and the carb is apart on the bench, so why not.
FYI, There was an article last year some time in PHR on building a carb for road-racing use and I remember them using modified floats and jet extensions, among other tricks. So I just ordered ‘em. I suspect (assuming the primary side of the carb faces forward) that you could get fuel starvation under hard braking without jet extensions placing the fuel pickup in the center of the bowl, resulting in the typical hard-braking engine stall. I saw this a bunch when the Street car shoot out was at Road America last year.
At any rate, here is the float I purchased, notice the tapered ends.

FLOAT

[Rokker]

To me wmhjr you seem to agree with my conclusions....

I said :
"My theory is that I´m using up fuel on the straights, in the turns the bowls are very low, causing fuel to slush away from the jet´s and therefore the bog appears to be in the turns, But in reality it is just low on fuel."

I should have clearified more. When on the motor I am using up fuel in the bowls. Not so much to do with the straights, only I´m on the motor more. This was happening in the straights too, it would run out of oooomph but first in turns the bogs started happening.
My fuel system w stock pickups, and that red pump that flows 20gph @ 7 psi is not supplying enough fuel. At 600hp I´m using 60gph (Very approx). It is clear to me the pump is not strong enough.

I´ve decided to run a black billett holley 12-125, the "new" billet one that is internally regulated, and run 8an lines to carb and debating on 3/8 (cheap) or 8an all the way to carb. It flows 140gph @ 7 psi.

As for pickup in the tank I probably have the smallest line, a 1/2" pickup would be best for sure. Might make a small sump in the rear with 8an instead of the $150 fuel sending unit.

If I´m reading you right we do agree on this ? The culprit beeing my fuel system is to small for what the engine needs.

Now the big question, how many gph is a holley 12-125 able to suck out of the tank with a 3/8 or 5/16 fuel line ? Not enough Is my guess...

Low on cash right know, so will probably do the pump and fuel lines first, and then if problem doesn´t go away, l´ll have to do the homemade sump.

[wmhjr]

To be clear, I don't think you're using up fuel in the straights. I think you're using up fuel anytime you're on the motor - period. Including in the turns. I think you're sort of on the right track for a solution but it's a different one than I'd pick. I'm just not a fan of electric pumps on non-FI motors if there isn't a good reason, and if you have a stock type tank and a carb I MUCH prefer the reliability, performance and simplicity of a good mechanical pump. That's just me.

I also do NOT like internally regulated pumps. I strongly prefer a separate, distinct regulator after the pump. Also a personal preference, but I cannot imagine ever using an internally regulated pump myself. Far too inflexible and frankly more of a maintenance challenge. No upside for me.

-8AN to the regulator (meaning from tank, through supply and pump to regulator) will serve you well. Anything more than 3/8 to the carb from the regulator will be overkill, but -8 won't hurt. It does make plumbing a little more bulky and packaging a little tougher.

In any case, directionally you're definitely heading in the right direction.

[Rokker]

I would like to run mechanical but the early ZZ502's does not have a provision for mechanical fuel pump...
The 12-150 is 25 dollars more and includes a regulator. Better to use that one then.

Turns, straights... I'm running out of fuel.

[clill]

Has it always been doing this or did it gradually start happening ? Sounds like you are on the right track if it has always been happening. Is the gas tank vented enough ?

[Rokker]

Clill, it´s hard to say. I´ve had some small signs of it happening but never as much as this, never just dying on me. Except for one time I was street racing with a friend, I had a a/f gauge at the time and it was def leaning out.
Filled up the tank, and it was good.

My tank ventilation consists of a 2mm drilled hole in the cap. For some reason the old one was blocked so I just cut it off. I´ve been thinking I should drill and tap a hole for a barb hose connection in the filler tube.
What would be sufficient ? wil -10an be enough ?

I know I seem like an idiot posting this, but it´s better to be honest and get help than faking how fantastic my car is. I´m not really this stupid
but the car has so many issues to take care of, and is an ongoing project with taking one step at the time. The fuel system have for the street worked ok. I don´t like fixing stuff that isn´t broken. Now it is "broken" and it´s time to fix this for good, and never look back.

I appreciate the help guys, and steer me right if I´m being stubborn on stuff:-) I like to think I´m Frank Sinatra sometimes and do it my way.

[wmhjr]

Originally Posted by Rokker

Clill, it´s hard to say. I´ve had some small signs of it happening but never as much as this, never just dying on me. Except for one time I was street racing with a friend, I had a a/f gauge at the time and it was def leaning out.
Filled up the tank, and it was good.

My tank ventilation consists of a 2mm drilled hole in the cap. For some reason the old one was blocked so I just cut it off. I´ve been thinking I should drill and tap a hole for a barb hose connection in the filler tube.
What would be sufficient ? wil -10an be enough ?

I know I seem like an idiot posting this, but it´s better to be honest and get help than faking how fantastic my car is. I´m not really this stupid
but the car has so many issues to take care of, and is an ongoing project with taking one step at the time. The fuel system have for the street worked ok. I don´t like fixing stuff that isn´t broken. Now it is "broken" and it´s time to fix this for good, and never look back.

I appreciate the help guys, and steer me right if I´m being stubborn on stuff:-) I like to think I´m Frank Sinatra sometimes and do it my way.

First, I'll try not to comment on the "street racing".....

I wouldn't be too crazy about just a 2mm hole drilled in your cap for vent. Remember that from the factory, the OEM type barb was much larger than that and it was for cars with very small diameter fuel supply and relatively small demands as compared to what you need. So, it sounds marginal even with a much less demanding motor. With what you have, a 2mm hole is probably not even close to being enough. If you're going to end up sumping your tank (which again, I would probably not do if I were you - the replacement sending unit provides some additional advantages) then I would also at a minimum put a decent sized connection on your tank for vent. To me, the better option if you're going to keep that tank would be to just get the darned replacement sender/pickup, which will have both feed and return/vent connections on it. That being said, you don't need anywhere near -10AN for vent. -4 or -6 would be perfectly fine.

That being said, I'm not sure if you can really attribute the issue to lack of sufficient vent, only because if that were the case the problem ought to be a bit worse with the tank pretty well full rather than pretty well empty. The lower the fuel level in the tank, the more vapor volume as opposed to fuel volume and the less impact I would think vent would have just as a guess. I could be completely wrong though. And no matter what, the vent issue should be corrected anyway.