Car bogs in the corners, road race.
 

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.

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 ?

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.

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.

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

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 ?

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.

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.

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: