steveiguess

I have had this car for years, it now has a 508hp 383 in it with a built th350. I let it warm up and drive it and if i get on it it will fall on its face sometimes. I just put on a new holley electric blue pump out back with another adjustable fuel pressure regulator. I can pop the hood while its hot and the filter will have little or no fuel in it but air, and the fuel psi will still be the same and the car will stumble..

any ideas? i dont think its vapor lock because the pump is back by the tank, the pump is brand new. i also just re built the carb...

the car came with a 305 with a mech pump, so there was no pump in the tank, i took the hard line from the tank and put rubber line in route to the pump, then rubber line to the hard line to the motor, i will include pics.
I cant figure out why its acting up...

also i have a vented cap on the gas tank...

Thanks

Damon

Is that one of those glass filters with the removable screen element? If so, that's possibly the problem. They look trick but don't flow worth a damn. Get a cheap Fram G3 filter (it has 3/8" hose nipples on either end just like your existing filter). The difference in flow between the two is dramatic. When I pushed over 400HP I found the limits of that glass filter- fuel pressure would drop off in the upper RPMs at WOT causing a stumble at the top of 1st gear or the bottom of 2nd most times. Put on the Fram G3 and it was rock steady all the way up, stumble completely gone. If you can run 2 filters- one for the carb, a separate one for the nitrous system- that would be even better.

No filter will ever fill up solid with fuel. There's always air in them. Don't know why, but mine always have air trapped in them and it's never hurt anything.

Also, that T fitting in the fuel line between the carb and nitrous system is going to be restrictive. Get a Y-fitting or run separate lines off your regulator's body if there are multiple attachment points. If you don't want to do any of that then at least make the connection to the carb the "straight through" path and have the line to the nitrous system be the 90* bend (the carb will have greater fuel demand than a 150HP plate shot). DON'T make both of them do 90* turns.

steveiguess

ill try that tomorrow thanks, ill get back to you on it.

jfyi i have never sprayed this motor, and i didnt plan on using the T fitting, etc, i was gonna get a cell with seperate pump for the n20, cant believe i sprayed my old motor with a 150 shot with it like that!

steveiguess

that didnt fix the problem, took it to the track because i thought i had the problem fixed. took off out of 1st, shifted into second and at 4 grand the car didnt go anywhere, no pedal, nothing, it didnt shut off just stayed at 4 grand and then i let off and it sputtered and it recovered itself and got going again and i limped it down the track...

hoseman007

My guess is that youre starving the engine for fuel when youre doing a hard launch i would suggest getting a holley black pump your blue pump flows 110 gph and the black flows 140 gph with you having so many ponies you need lots of fuel when you accelerate hard.

steveiguess

i ran it like this for a good 6 months with no problems... (the blue pump that is)

Gumby

Ya got a hole in the fuel line somewhere. That bit of metal line on the sending unit likes to rust through. Gotta drop the tank if ya can't find any obvoius ones.
[ I ended up cutting mine back a good 3 inches to lose the pin holes in mine.

You can also rig up and electric pump with a gas can to reverse the flow, that will help track it down. That trick work on an Olds wagon I had once. Made the leak very obvious.

But the latest one I swear I could put my pinky in the hole in the rubber fuel line but the car still ran.

Kinda like a pin hole in a straw, It works until you suck to hard.
Then ya just get air.

steveiguess

any other possibilities?

rgarcia63

You might try remounting the pump at a lower elevation.