Okay I have a 87 Trans AM which came with the H motor but switched in a 350 chevy crate 4 bolt and 650 cfm edelbrock. My mechanical is a 3/8" gas inlet, and 3/8" flare outlet, but there is also a 1/4" I'm assuming overflow line that goes back to the tank? I ask because when i hammer on her she stutters a bit and I am always having a problem with fuel adjustments. Though the main question is do i need that mechanical (3/8 Inlet, 3/8 Outlet, and 1/4 Return)? or should i use a standard 3/8 Inlet & 3/8 Outlet w/ a 7-8psi?

 

The extra line is a return line, used to help with the vaporlock issues the carbed cars are know for. You may not 'need' it.

I had the edelbrock cards in the past and they were the biggest pita. I would say your issues are carb or ignition related, not so much the pump itself

 

I'm guessing you have the mechanical pump that has the return line built into it. The 1/4" return line should be good enough for that.

Edelbrock recommends 5-6 psi for delivery on their carbs. Do you have an adjustable pressure regulator between the pump and carb? The factory fuel pumps will and can very in fuel pressure from one unit to the next and the pressure can change as the motor warms up as well.

 

If your pump has a return fitting, then you must use a return line.

If you're choosing a new pump, then there's not much reason to not run one with a return line.

 

A new "Stock" style mechanical fuel pump will run like $30 at Autozone or O'Reillies. They will have the return line on them. USE THIS, if you don't it'll cause problems. Also, most of the Holly and Edelbrock mechanical pumps are race pumps with no return line and run upwards of $70 or $80.

 

There's more in play here. '87 carb'd V8 cars came from the factory with an in-tank electric pump. The in-tank electric pump NEEDS the return from the mechanical pump to allow it to maintain a steady flow of fuel to keep the pump cool. If you aren't running a return, you'll have two problems: 1) the electric pump will eventually burn out; and 2) your fuel pressure at the carb will be too high.

Hook the return back up like it's supposed to be (it's 5/16", by the way, not 1/4" - the 1/4" line goes to the vapor canister).