I have an 87 Z28 with an electric pump in the tank and mechanical pump on the block. The electric one feeds the mechanical. Anyone know what PSI the electric one puts out?
The mechanical pump has a wierd setup with one inlet line from the electric pump, one output to the carb, and one overflow back to the tank. I want to upgrade my mechanical fuel pump to an aftermarket high flow one but dont know if I should get a pressure regulator or not.

And does anyone know what would happen if I just ran the electric pump right into an aftermarket mechanical pump? Will the electric one burn up or anything? Cause aftermarket ones dont have an overflow port.

If it was me I would not use the mechanical pump at all. I would just buy a Mallory three port regulator and use the in-tank pump.

Put on the mechanical you want. if the pressure is too high, then get a $20 reg. It shouldn't be tho, most mech pumps are self regulated to a safe range.

I just put on a 120gph carter mechanical on my 87 formula with both pumps. All you have to do is T the return and supply line together before they enter the mechanical pump. The electric pump supplies fuel on a 3/8s line, excess fuel is then returned by the 1/4" return. The difference in the line sizes causes a slight positive pressure at the mechanical pumps intake.

So far this systems working great! No problems at all. Car runs much better too.

Edit: found a pic:

fuel pump pic

Thanks guys,
I'll go ahead and try the tee idea before the intake.

My question is which setup is better.

1. Using the mallory 3-port reg and return line with factory pump

or

2. Adding a mechanical pump with the factory in-tank pump, a regulator and running the lines to the other side of the car.

Which would be the best system and also taking in consideration of cost?

I don't know which way is actually better, because I have never used a mechanical pump. I went with the Mallory because the in-tank pump worked and I didn't have a mechanical pump on hand so I was going to have to buy one or the other. I have heard that using the Mallory regulator with and electric pump can sometimes cause a pressure spike, but I haven't had any problems.

I am getting ready to change from TPI to carb and planning to use the mallory AFPR. I just figure if the in-tank pump worked, why not use it. Alot less work involved. Then if the in-tank pump goes, I could just put in a pickup and a external electric pump then.

Nothing weird about that. That was the standard setup prior to the use of the in-tank electric.

I'm using a standard replacement AC pump on mine with absolutely no fuel delivery issues (no in-tank pump). Granted, I'm 50 cubes short of yours, but I seriously doubt you would have any trouble with a standard pump when it has the electric pushing fuel up to it. No regulator required, either.