Car bogs in the corners, road race.

[Rokker]

I had my 65 Chevelle at the track yesterday. The road race cours is about 1 minute 10 seconds long with the best cars reaching 120mph and going around 75-80 in most of the turns.

Overall, being my first track day event, I totally enjoyed it. The sc&c suspension system held up great and I would have passed a few cars on 15" tires if it hadn't been for one Big issue.

When pushing the car in the turns it starts to bog and stutter when going in to the pedal, it keeps stuttering for a while down the straight and then looses all power. If I let go and drive slow it cures and works fine until the next turn and then it starts again. I've never noticed this when pushing it on the streets, but now that I now I notice the same thing happen there. Also when doubt donuts it will suddenly loose power.
I have my suspicions on what is wrong but would love to hear you comments! This will not happen that much in the first laps, but when starting to push the car it becomes a big problem.

Combo:
Stock fuel tank and Lines
Holley red pump in the engine bay
Prosystems double pumper, 1000 hp
ZZ502 with cam and 11,2:1 cr.

I tried:
Fuel bowls 95% full glass - same problem
Fuel bowls just under glass - same problem
Front fuel bowl at 40% and rear under the glass - same problem
Backing off the timing alot - same problem, ran like a dog.

What do you believe is happening ?
I know my fuel system is not the best, but has been working fine on the street so haven't messed with it.

[Rokker]

I forgot to add, I run a HEI with 90 degrees plug wires and 5-6 of them is touching the headers. I am wondering if I might be getting a bad spark at some of the plugs as the heat rises and the rubber get's softer and might be bringing the wires close enough to create a spark between wires and manifold ?

[wmhjr]

My guess? Non-sumped tank and losing fuel pressure when you add lateral force. What were your fuel levels when this happened? Stock pickup and sending unit?

The one constant you have every time this starts is that the car is in a relatively heavy G turn. So what changes in that situation? Fuel displaced to the outside on a flat tank with stock pickups. Pump starts getting air as the fuel moves away from the pickup. Initially there's enough in the bowls to run the motor, but under heavy throttle that will burn quick. Keep on the throttle and even after the pump stops cavitating, it can't catch up initially. Slow down in the straight, backing off the throttle allows the pump to get some fuel back in those bowls.

Somebody else could have a completely different opinion.

[Vegas69]

I agree, always race with as much fuel as possible. You dropped your floats so that shouldn't be the problem. I would reccomend a road race rear float and jet extensions, but I highly doubt that is your problem, especially the first time out.

[PSV]

I may be way off base but I think your pump needs to be in the rear of the car by the fuel tank as its designed to push fuel. You may be usng more fuel than the pump can replace with it it the engine compartment and only a short run to the carb.

[NOT A TA]

I may be way off base but I think your pump needs to be in the rear of the car by the fuel tank as its designed to push fuel. You may be usng more fuel than the pump can replace with it it the engine compartment and only a short run to the carb.

^^^ this

[Rokker]

Thanks for the ideas guys !
Fuel level was about 1/4, so I went and filled it up. Same symptons.
Yes, stock pickup and fuel lines, probably the smallest type.

Vegas69, any links to those floats and jet extensions ? Maybe not the problem now, but might be next time.. One funny thing, my cousin who is a far more experienced driver had way more problems with it than me... Who would have thought... lol

So, first thing I chould do is move the red holley pump to the rear. If that doesn´t cure it then how much pump will I need in gph to feed a 502 pushing 600 hp.

An upgrade in fuel department seems to be the way to go.
Pump, regulator, filter, fuel line, fuel sending unit etc. Will a stock 3/8 be enough from the tank, and then fuel lines of 1/2". Or where can I get 1/2" fuel sending unit ?

[Rokker]

Although the red Holley is rated at 97 ghp, it is down to 20 ghp a 7 psi :wow:

Even the blue holley would be a major upgrade pushing over 90 ghp at 7 psi.

Looking at either the black pump or the hp125..
black is 125 gph at 7 and needs a regulator.
hp125 is 110 and internally regulated, which I like, especially if I`m not going to run a return line, which I haven´t decided on yet.

[mike343sharpstk]

I have the same issue with my car, and I firmly believe it to be the carb. If I corner at a certain lateral load I can make the car shut off like a light switch. However in my case it’s an old Carter.
If the fuel pump is failing it would not occur at the exact second of max side loading. If the fuel pump fails there is still a fair amount of fuel in the float bowl, and when cornering you are typically at low throttle so fuel is getting sucked out of the float bowl at a relatively low rate. The fuel is there in the carb, but not in the spot where the pickup is trying to suck it into the motor.
I’m currently finishing up my Holley carb and while it’s still off the car I’ll be adding jet extensions and a road race float to the primary side of the carb.
Time will tell how it works, it can’t be worse.

[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.. :thumbsup:

[wmhjr]

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.. :thumbsup:

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]

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! :thumbsup: 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 (http://www.summitracing.com/parts/QFT-16-15/)
http://static.summitracing.com/global/images/prod/large/qft-16-15_w.jpg

[Rokker]

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

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]

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"..... :soapbox:

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.

[Rokker]

We where going from 0 to 100mph in a closed piece of road a long way from any public. Not a biggie to me... Sounded worse I guess.

What features does the sending unit offer ?

The tank needs to go down anyway for the mini sump anyway, adding a venting Hole in the filler neck would be the easy part..

I run a autometer fuel level float to the autometer fuel gauge not the stock one in the dash.

[wmhjr]

We where going from 0 to 100mph in a closed piece of road a long way from any public. Not a biggie to me... Sounded worse I guess.

What features does the sending unit offer ?

The tank needs to go down anyway for the mini sump anyway, adding a venting Hole in the filler neck would be the easy part..

I run a autometer fuel level float to the autometer fuel gauge not the stock one in the dash.

Like I said, I'm trying to stay away from the street racing thing. There is no such thing as a "closed piece of road" that you can control access to preventing accidental animals, hikers, bicyclists, etc from getting there - and unless you personally own it, you're taking chances with other peoples property and lives. I'll stop there though there is a LOT more that could be said with no possible excuse. Maybe I'm a little sensitive about it because I live in a rural area, and there are all kinds of nitwits who think that because it's the "country" they can drive however they want with a total disregard for other people. Nothing like being on a tractor along a quiet road and having some dbag out of control come flying up, fishtailing trying to slow down and honking their horn because they think YOU are creating the unsafe situation. And it's those dbags that make it more difficult for the rest of us. Thank them for more and more laws making our hobby more difficult than it already is. Nuff said about that.

Anyway, the sending unit has better pickups, is high quality machined billet, can have -AN fittings, provide your volumes and vents, etc. If you're not running FI, sumping is simply not necessary assuming the remainder of your fuel system is properly setup. I have seen where people making their own sump ended up causing them problems because they didn't anticipate where the fuel would actually be in different scenarios. It's tougher for a car in the twisties than a drag car.

[Rokker]

Here´s a video from that day. After we had autocrossed all day we took the cones away. Lined up two and two cars. I raced a turbocharged 944 and lost as my car was giving up in second gear. The stalling might actually be from this very issue, but I have since changed the carb and given it more initial timing so I think actually this was more because of flooding from the secondaries. Not at all sure though, seems like I´m on the motor for long enough time to empty the bowls even here...

Not bragging about the driving or anything, but showing the scenary so you can cut me some slack, it´s not exactly like we trying to provoke any tractoring farmers.

http://www.youtube.com/watch?v=t-CSdcsFKTw

What is better pickups ? It´s just a pipe going in there that has a 1/2" wide hole in it, maybe without the sock I understand the stock system has ?

I´ll consider it though, it´s more a budget situation rather than what I like. A nut with 1/2" or wider to an 8an or 10an in the bottom rear and middle of the tank would seem to be an ok plave to put it to me. That´s about where the "stock sending" unit is picking up anyway right. If it doesn´t work I´ll plug it and get the $$ sending unit.

[orangevert]

I had a 950 Prosystems and if I braked really hard with it. it would want to bog out as well.

[Rokker]

Going road racing tomorrow so the new fuel pump got temporarily installed.
Engine compartment is done. Thank you guys for all the help !

I´m planning to open my fuel tank in the winter, make a room with baffles to keep the fuel available, on acc, deac, and lateral movement. Four baffles. And will use a 1/2" tube in the stock pickup. The idea of a 90 degree bend in the bottom of the tank would look like crap. I found that out after I got the parts. Big heavy lump, that will stick down to much and easily will get hit by a rock or hitting something while backing up. For now this will have to do. The fuel pump will be moved to the back too.

Felt like it picked up 100hp on top of second gear.

Plumbing part one :-)

http://i37.photobucket.com/albums/e97/Rockern/IMG_1273.jpg


Here´s the red pump versus the Holley HP150.
The red one is like a baby, compared to the sturdy piece of engineering the heavy HP150 feels like.

http://i37.photobucket.com/albums/e97/Rockern/IMG_1267.jpg


I also found that when adding pressure from the new pump, the primary needle and seat wouldn´t hold the fuel back. Fuel bowl was full of dirt, rust etc. probably could have saved me the fuel pump install, but it sure feels good to have a much better fuel system up and running.

[Rokker]

Mounted the pump in the back where it should be. And AN8 fuel line from tank. Will modify the pickup in the winter and make a baffled room for the pickup inside the tank.

http://i37.photobucket.com/albums/e97/Rockern/76d45ea3.jpg

Car still bogs in the corners even in low speeds, not running out of fuel. It´s noticable even in roundabouts now. Seems even worse after the fuel system upgrade, maybe the fuel bowls are filled faster now ?
Any other suggestions are welcomed. Hopefully some that doesn´t cost me as much as the fuel system.

What do you guys say ? Road racing floats ?
I don´t believe rear extension is the cause of my problem, as this happens even while only using the primaries.

[wmhjr]

Wow. That sucks. You might try one thing. Reset your system so the bowls are 25% and no higher and see if anything changes. Just a thought - don't know if it will have an effect or not.

[Rokker]

After my last post i noticed the car would have bad idle qualities and stopped a few times. Left the pump on but engine off. Was dripping from the secondary boosters. I`m running 7psi, took the needle and seat out, cleaned. Did not see any debris on it, but has been fine since.

I would love to mount a camera inside the fuel bowl to actually see what is happening when I`m turning. As the problems where worse with higher secondary fuel level when the needle and seat wouldn`t shut off, I think this is a good indication that what is happening is "fuel is going places where it shouldn`t be right" ? I don`t see how a rear jet extention would cure this, as we are talking about lateral movement not acceleration mainly.

What carb mods should I try ?

Btw, when at the track I ran the bowls real low, and real high. Both the same and one high one low etc. So I kinda feel it`s something a fuel bowl level won`t cure. It behaved exactly the same on the track no matter what.
Btw, let`s not rule out timing, mechanical stuff etc. I`m all ears. Man I need to talk to Patrick.. Thanks, for the help guys !

[Rokker]

Wow. That sucks. You might try one thing. Reset your system so the bowls are 25% and no higher and see if anything changes. Just a thought - don't know if it will have an effect or not.

As for now, I think this is my best bet, so I`ll try it out one more time. Worst case scenario, it didn`t help right ? :thumbsup:

[Vegas69]

Your carb is either set up incorrectly or it's missing a part. Specifically, a bowl vent baffle or extension. A bone stock carb isn't going to give you these problems.

[Rokker]

Your carb is either set up incorrectly or it's missing a part. Specifically, a bowl vent baffle or extension. A bone stock carb isn't going to give you these problems.

This is a custom made prosystems carb, untouched. So what parts should I look at to see what is missing ?

[Vegas69]

This is a custom made prosystems carb, untouched. So what parts should I look at to see what is missing ?

Send it back to Patrick, no way should it be acting up like it is currently. Their is normally a plastic baffle that runs from the metering block. Does it have vent tubes sticking out of the horn?