Hey guys, I have a 85 trans am that was equipped with the lg4 ccm carb and factory mechanical fuel pump. My question is I am replacing the engine with a centerbolt 87 and up engine and I want to add a fuel pressure regulator and keep the mechanical fuel pump, but the factory pump has a provision for a return line. Can I use a 2 port mechanical pump and connect the factory return line to the adjustable regulator? Or do I need that 3 port mechanical fuel pump? I am using an edelbrock carb.

 

So what engine are you putting into the car that will determine what pump you need. Also you will have to make sure it is drilled for the fuel pump pushrod.

 

Engine is a 350 and yes it is drilled out for a mechanical pump. Just need to know if I can go with a 2 port pump instead of a 3port and use a pressure regulator.

 

Sure you could do that, but it would be totally pointless and unnecessary.

Your stock pump will support near 400 HP. Speaking strictly from having used one on a 400 at that level for over a decade. I would recommend using a lightweight fuel pump drive rod such as the Moroso, to extend its RPM range, which is what I did.

 

Can't see why you couldn't get a 2-port FP and use the regulators return port,... Isn't that what it's for ?

I've learned that Edelbrock carbs almost require the use of a FPR,...... if the fuel pressure is too high then fuel can/will push into the carb. This picture was taken after shutting off a car with a ( Fresh, professionally built ) Edelbrock Carb without a Fuel pressure regulator. You can clearly see the fuel is still pushing/filling into the carb even with the car not running.




This is how I ran the last carb/regulated fuel flow to an Edelbrock SCB that I built using a factory style fuel pump. ( Don't buy cheap parts store fuel pumps,.. they have a weak lever spring in them that can cause a audible "Click, Click, Click" every time the pumps lever moves up and down - matching engine RPMs. ( sounds VERY MUCH like a lifter tick or a cracked flywheel !)



* note; I used a dead temp gauge sending unit as a plug on the FPR return port. If you use this type of set-up,... use a real plug !

Once everything is installed just dial in the FPR till you get good readings and you should be G-T-G !




The only time I ever used a 2-port Fuel pump in a Thirdgen I didn't use a FPR on the system,...... to connect the return line on that set-up I used a 3 port fuel filter from some late 60's Chevy.

 

I think the Edlebrock carb with the fuel dripping after it's turned off might have a different explanation, that being, the fuel in the pump boiling, from the heat of the block.

I've had that happen to me with Holleys and Q-Jets, so I see no reason Carter would be any different.

A regulator in that case, while it might "fix" the symptoms, isn't the "solution" to the problem. Thermally insulating the pump from the block would be a better approach. https://www.cantonracingproducts.com...&category=8510 Or even, just stacking up 2 or 3 gaskets both under the plate and under the pump. The WORST trouble I ever had with that, was one time when I had to replace one under duress, and the gasket was missing from the new pump; sitting by the side of the road, I just put the pump on with silicone, and while it didn't leak oil, the carb boiling problem was SO BAD, the car was almost undriveable. If I drove for awhile then turned the car off and started it back up in 10 or 15 minutes, it would be all but impossible to start and would then blow out black smoke for a half-mile before it calmed back down again.

I've used the 3-port filter also (stock for 69 Chevelle SS396), worked great.

 

Edelbrock carbs are sensitive to fuel pressure, and the instructions state not to exceed 6.5 psi.

 

A stock (ish) pump puts out something in the 4 psi range.

 

This is What I have in mind to plumb a 2 port mechanical fuel pump to a adjustable regulator.

 

The Carter M6626 is a popular fuel pump for SBC's. Summit lists it at 5.5 to 6.5 PSI, but the Carter site states a maximum of 9 PSI. Which is correct?

I used this pump with an Edelbrock 1407 and had a fuel dripping issue. It went away with a regulator set at 6.

 

This problem has ZERO to do with under-hood heat.


I already knew what the problem was when I took the pics; it's not the first - or the only - time I dealt with it. Started working on it first thing in the morning on a cold car,... started it long enough to kick the idle down, shut it off, and took the pic to document the issue. Problem was gone after the FPR was installed; never to be seen again.

Here's another pic of a different car with a ( pro rebuilt ) Edelbrock,... Look familiar ??




The cheap parts store pump was making almost 9 pounds,... and the Edelbrocks simply can't handle it.