Big E, or anyone... Still having horrible carb problems!

[DUB]

High banked 1/2 mile, had a hell of a time! Stumbling off corner badly, have tried almost everything.. He told me it happened a few times going into the corner under full throttle. I just ordered a VDL carb!

New question on fuel pressure:
I run the Carter Mechanical and it says 4.5-6.5 operating fuel pressure, I hooked a gauge up to it and it runs 6 at idle and pulls down to 5 psi at 3,500 rpm. Is this normal? I am being told by fellow racers to run an electric Holley blue and run 6-7 psi. Thoughts?

[CnDRacing]

We run the Holley blue pump and regulator set at 6psi (6an fuel line, no return) with no issues. 1/4 mile track at about 8000 rpm.

[Headhunter]

VDL will tell you what pressure you should set it at. I always ran 4 psi.. and had a issue with a carter electric not able to pump enough volume. Would emty the bowl sputter and when I got back on the gas would be flat then the bowl would fill and motor would go again. I spent 4 weeks chasing carb issues before I figured out that it was the CARTER fuel pump. Have been told they had the same issue with both the electric and the mechanical carter pumps.

[Headhunter]

Could also be pull over from the accelerator pump system.

[DUB]

I really don't think that this is pull over...

It is fuel delivery some how or another float, float level, pump or something.. Do you mean the Carter mechanical pump that you had problems with?

[Headhunter]

I had problems with the electric but another had the mechanical and had the same problem of not enough volume to keep the bowl full. I guess I should ask , are you sure the fuel system in clean and has good flow from the cell to the pump and the vent is not clogged and making it tough to get fuel to the pump? Kinked or damaged lines both in the cell and to the pump?

[DUB]

I have 3/8 braded steel line all the way from the cell to the pump and up to the carb with a large inline filter in the rear of the car. Everything is clean and flows well. The carb is a box stock brand new KD4412 500, everything has been replaced in the carb with the same results.

[CnDRacing]

Have you checked the pickup in the fuel cell? Had an issue once and the hose was bad at the bulkhead fitting in the cell.

[DUB]

That's a good idea... I think I will tear the cell apart and check it all out!

[Headhunter]

It may flow good when there is positive pressure but even SB line can colapse under vacuume...

[84Dave]

And the carb itself? We found that the 500 Holley performed best with a float level that allowed the fuel level in the bowl to be about 1/16" BELOW the thread bottom on the bowl sight plug...... engine warm. The other thing was the size of the accelerator pump 'squirter'. We had to go from the stock #28? all the way down to a #18-#20 squirter. The stock large squirter caused the 231HP engine to 'stumble' out of a corner. And if the float level was too high, hard entry, out of the throttle, into a corner caused raw fuel to be dumped/pumped into the intake manifold, which caused a 'stumble' mid-turn with throttle application. Float? We initially ran the brass float. Removing & 'shaking' the float revealed fuel inside the float. Inserted the float in a pan of hot water & air bubbles revealed themselves from the poorly soldered float seam. Re-soldered the float, set the fuel level with the engine running, smaller squirter, and the thing ran like a scalded dog on the race track! Oh...... and we replaced the rubber o-ring on the needle/seat assembly every year/season. We experienced the problem of the o-ring leaking with good fuel-pump pressure. That caused an excessive fuel level in the bowl once the engine came up to temp. All the parts in the carb must work together! -Dave-

[return to dirt]

And the carb itself? We found that the 500 Holley performed best with a float level that allowed the fuel level in the bowl to be about 1/16" BELOW the thread bottom on the bowl sight plug...... engine warm. The other thing was the size of the accelerator pump 'squirter'. We had to go from the stock #28? all the way down to a #18-#20 squirter. The stock large squirter caused the 231HP engine to 'stumble' out of a corner. And if the float level was too high, hard entry, out of the throttle, into a corner caused raw fuel to be dumped/pumped into the intake manifold, which caused a 'stumble' mid-turn with throttle application. Float? We initially ran the brass float. Removing & 'shaking' the float revealed fuel inside the float. Inserted the float in a pan of hot water & air bubbles revealed themselves from the poorly soldered float seam. Re-soldered the float, set the fuel level with the engine running, smaller squirter, and the thing ran like a scalded dog on the race track! Oh...... and we replaced the rubber o-ring on the needle/seat assembly every year/season. We experienced the problem of the o-ring leaking with good fuel-pump pressure. That caused an excessive fuel level in the bowl once the engine came up to temp. All the parts in the carb must work together! -Dave-

all good but on the float, if you are running alcohol then do not run a brass float. if you have a backfire it will crush and distort the float. have seen it happen. gas, brass ok. alky, brass bad.

olin

[84Dave]

Points well taken, Olin. And for those teams running street/pump gas, which now in the large majority of cases contain 10% Ethanol, that o-ring on the needle/seat assembly may be degraded quickly, unless the o-ring is of material that will tolerate the Ethy? -Dave-

[Headhunter]

And it will degrade the foam in the fuel cell also.

[Big E tech]

That's a good idea... I think I will tear the cell apart and check it all out!

What did you find out inside the cell?