shadow315

iTrader: (3)

Ok, so I am working on my 92 build again. I was about to place an order on Summit when I bumped into some concerns here on the forums.

I have a 350 w/ carb going into this 92 which used to be TBI & has in in tank pump. I already have a mallory 4309 sitting here in the box ready to use and I was just about to order some braided fuel line & -6 AN adapters for the fuel feed & return lines. Many of you are running this set up and there are decent pictures of installs on this thread.

Anyways, I just discovered several people have had issues with "jumping" fuel pressure. Thoughts on this are the return line is too small or that they had a cheap and useless gauge.

My question is, have we put this issue to rest?

I don't know if I should go ahead and order the remaining parts or pull the tank and change to a different pump (or both). I suppose I could just order the parts and see what happens... but I read multiple threads and there was a lot of good input, including Mallory's advice of a 3/8 return line but a lot of people are saying it works with no problems..

Thoughts?

travis401

iTrader: (1)

if the return line is clogged, itll cause pressure to raise. if the return line is freeflowing, you wont have an issue. i run a reg on mine with a higher pressure pump than the tbi, and it works fine. i keep a steady 5.5psi. i had that setup feeding a 350 stroker that was droping about 400hp before i pulled the engine back out.

Ozz1967

iTrader: (4)

I have to run a second regulator because my 4309 won't bring the pressure down far enough (Sits about 9psi). I replaced the mechanical block pump with a 255lph in tank pump. I ordered some braided line and adapters to hopefully free up the return line a bit and hopefully that will fix my issue. I'll post more when I get it done.

Damon

I've used them in serveral vehicles with stock TBI pumps, stock TPI pumps and a Walbro 255 in my 454SSS truck, all feeding carb setups. I have had NO problems at all with fuel pressure- high, low or fluctuating. I can dial it down to about 3 PSI (lowest it will go with the low pressure spring and the screw backed out as far as I dare) but usually run about 6 PSI. I've checked it at idle, driving around town and at WOT and haven't seen more than 1 PSI fluctuation in pressure between any of those readings.

This is with stock 3/8" feed and 5/16" return lines and filtered through a stock fuel filter back on the frame. I didn't even remove the stock flex lines- I just cut them and tapped into them with barbed fuel line unions and high pressure EFI hose to the regulator ports.

I can imagine a bad regulator is produced from time to time, as well as some vehicles having parially obstructed/kinked return lines. I also wonder if anybody might be capping the boost-reference port on the regulator (don't do that- leave it open) or running it to a vacuum source for some reason (don't do that either).