del91_305

I recently got done with my head/cam/intake and TBI to carb swap, and im having a heck of a time getting it running right. The problem im having is, i can let it sit and idle for a while and like today i took it out for a drive and all the sudden it just stalls like it is out of gas. Then i can try to start it and it take a few times but finally it will start again. When i turn it over i can hear it sucking air through the carb like there is no fuel. The pump was replaced 2 winters ago and it sounds like its working fine, im as using an inline regulator running 3 PSI. What could it be?

Lo-tec

You need more than 3 PSI of fuel pressure. Is this a return style regulator with the factory electric pump in the tank?

del91_305

Yea it is a return style with electric pump, but for some reason i cant get it to run anymore than 3 psi but ill try again

screaminformula

it sounds to me that your float level is too low and the engine is sucking the bowl dry. reset your float level to a slightly higher level and i think the problem will vanish. the sucking air you are hearing is the carb sucking air, go figure, trying to refill the float bowl that just got sucked dry...

Josh

edit* didn't notice the whole 3 psi thing...GET SOME FUEL PRESSURE TO THAT BEAST!!! also, check floats

Air_Adam

Floats are set too low, and 3psi is not enough fuel pressure... you want around 5 or 6 psi.

five7kid

iTrader: (14)

I'll put my oar in and say there's nothing wrong with the floats.

3 psi probaby isn't enough. Exactly what type of regulator are you using? There's been so much talk about "3 port regulator" around here that people think the $25 Holley reg with an inlet port and two outlet ports is a "3 port". It isn't.

del91_305

Well it has a line that says in and then 2 that say out. I am using on out for a return and one for the carb. Also i just got done messing with it some more, i have an inline pressure guage also and when i turn the key on i could hear the pump and i saw the gauge move up a little, but then when i get it started and watch the gauge, it doesnt move, sometimes if i hit the throttle it will move a little and thats all.

Lo-tec

If you do not have a major restriction in the "out" port that is for the return (i.e. a solid fitting with a .020-.030" hole in it), all you are doing is pumping all of the gas back to the tank. GM sold a fitting for the return on the regulator of it's 5.7L H.O. conversion engine. It has a .042" hole in it. Part # 10185093, retails for $53.94. It is just a brass fitting with a small hole. I would get a true return style regulator and do it the right way. You can probably do a search for the right part #, I think it is a mallory unit other members were using for this swap.

del91_305

Ok well do i have to run a return line? So on my regulator, it has two outs, is that to feed 2 different carbs? Oh and by the way the regulator i am using is by pro comp i think, it is a cheapy

Lo-tec

It's a mallory 4309 that you need. $75 from summit racing. Use the return line or you'll burn up the pump pretty quickly.

five7kid

iTrader: (14)

You need to run a return, because the in-tank pump relys on flow to keep it cool. Dead-head it, and you'll burn it out.

The two outlets on your current reg is for running a line from to reg to each bowl of a dual feed carb like Holley.

Another option is to put a needle valve on one of the outlets and run that as a return. Turn the needle down so that you always maintain 6 psi. But, that's hard to get right, so the best bet is to get a return-style regulator.

del91_305

So basically i can get a fitting that has a very small hole it in for the return line so that it puts some restriction on the return side and lets all the pressure go to the carb? I wonder if i could find one at a performance shop

del91_305

Where can i find a needle valve?

vrtc350

iTrader: (1)

Well I've been considering using that type of regulator and my question has finally been answered. I've been contemplating on just going with a mechanical since I already have the pump.

92MaroRS

Me and a buddy converted his 91 TBI truck to carb and am just running a normal regulator with no return line and the stock pump is still working, original pump, truck has over 130k miles, and has been almost a year since we converted it, no pump problem.