I have an 89rs that came with a tbi 305 from the factory. It now has a carb 350 small block, I am running on the mechanical pump on the motor and the electrical fuel pump in the tank that was there when It had the 305.
What I would like to know is can I delete the mechanical pump and just run of off the electric pump in the fuel tank?

Thanks...

 

Yeah, that's how you should be doing it already. In-tank pump plus a Mallory bypass-style regulator (4309, I think).

Not sure if you have a bypass style regulator in your system somewhere already, but the stock in-tank pump was not meant to be run "dead headed" against a mechanical pump or carb. Dead-headed pressure is too much for a carb (~14 PSI, give or take) and the pump's life is shortened without having a bypass-style regulator.

 

I know I'm pretty sure I am not running a bypass regulator on the the fuel return line. I can check the fuel pressure maybe tomorrow if I can get in to town and pick up a Little fuel pressure gauge.

If the fuel pressure is to high, then You think I should delete the mechanical pump and run this regulator?


http://www.streetperformance.com/par...8805-4309.html

 

If the mechanical fuel pump is a stock-style 3rd gen with a return, then you're probably okay.

But, that would be the correct regulator.

 

yes.

 

Well anyhoo I did find a fuel pressure gauge, but I still need to get to town it don't have the correct attachments on it.

I'll get a pressure reading tomorrow.

here's a pic of the mechanical fuel pump if it helps at all.

 

I just have one more question, if I do need to add a regulator does it really have to be a $90 dollar Mallory. because I have seen like holly's and elderbrock even the cheap one's at auto zone for around 20-25 bucks?
Not that I am trying to be a cheap *** I just dont have $90 bucks for a regulator right now.

And anyway I could not find the fuel pressure Gage adapter I was looking for at the parts store, So I had to order one. I wont know what the fuel pressure is for about a week now.

 

correct me if im wrong as im new to the car hobby but i've been told to get rid of the electric pump by many people due to it will wear out faster being restricted by a fuel regulator and i will have to replace it more often true or false??? sorry if im stealing thread thats not my intent as im in the middle of doing the same swap myself

 

The reason the cheap ones won't work is because they are not return style regulators. If you go with one of those, it will burn out the pump in the tank, which is by no means a fun job. I felt the same way when I did my swap, but to do it right you really do need to get the Mallory.

 

From what I've read in the past few day's, the electric fuel pump with a TBI 305 is a low pressure pump that normally puts out about 15psi, so for doing a carb swap or 350 swap you would need to run about 5-8psi witch should not be to much of a pressure cut back for that type of pump.

Now a Tpi Pump would put out about 35-40psi and cutting the pressure back on that one with a regulator would kill that pump pretty fast.

God don't quote me on this, it's just what I think I've learned in the past few day's.lol

 

I won't quote you, but I will correct you.

Even cutting down 15 psi to 6, you'll burn out an in-tank electric if you don't use a reg with a return.

 

Don't all regulators work off the return fuel line? Do you mean that a reg with a return, has it's own return line that is larger to go all the way to the tank?

Sorry if I'm asking to many questions,I've only been messing with small blocks for about a year now.

 

The $25 regulators are "dead head". They just cut off inlet flow when the set pressure is reached.

Return style are more sophisticated and therefore cost more. They control outlet pressure by restricting return flow.

In-tank electric pumps require a constant flow through them to keep from overheating. A return-style regulator provides that flow.

 

I Finley got that prusher Gage attachment in the mail, I checked the feed line after the mechanical fuel pump. I got 7.5 psi.

I also checked the presser at the feed line before the mechanical Gage and got 0 psi.

is 7.5 psi too much for a 350 with a mild cam and a ederbrock performer 650 carb?

I drive my camaro all the time and it makes good power in the low end but will really fall on it's face up top.

I also check the plugs and thay are nice and tan, no sign of running rich.