Hi Guys , I’m looking for some help here please, I want to put a carbureted 383 in my Iroc that had tuned port injection. I plan on changing the fuel tank pump to one of lower pressure. I’d like to eliminate the harness with the sensors since I won’t need them , the problem is I believe I will need to retain the fuel pump relay that’s in the harness for the pump to work. What can I do to solve this problem. Thank you in advance.

 

Just run a mechanical pump.

 

Sorry roller cam , can’t run a mechanical fuel pump

 

I thought roller cams still had the eccentric lobe for the pump pushrod.

 

Yes apparently you are correct, I guess I assumed that because it was a late model cam i5 wouldn’t. However doing the research it appears it does. Thanks for your reply..

 

Thanks for those 3 replies. This is a Gm 383 cam so apparently it does have a mechanical fuel pump lobe. I’ll double check.

 

Oh, the HT383 cam. Yeah, that has to have the eccentric lobe... that engine is largely intended for carburetor applications.

 

You can run the OEM in tank pump. No need to change that. Get a return style regulator, set it to the appropriate pressure for your carb, power the fuel pump relay from the oil pressure switch. Easy button.

 

Also a valid approach.

Only, the oil pressure switch should only be used to turn the relay on and off, not supply the main power to it. I know that's what you meant, but just to be 100% clear... lol.

Main power for the relay should come off the battery.

 

Yep. That's exactly what I was saying.

 

as said above, keep the electric intank pump and take the wire off the relay that goes to the ECM and hook it to an oil pressure switch instead. Use a return style regulator to bring the pressure down to 4-6psi. You couldn't pay me enough money to downgrade to a mechanical pump

 

I'm pretty sure the original carb'd cars with an in tank pump used the relay to activate the pump during startup, then once running, the relay switched off and the oil pressure switch takes over.
That's how I wired mine using the schematic from this forum. Worked like a charm.

 

I plan to use a mechanical fuel pump on my 383 installation. I have removed the fuel pump from the gas tank. How do I go about changing this over? Do I just put in a gas tank sending unit ? Is there a kit made for this ? Thanks for your input.

 

I just found out my in tank pump was bad . So I have that out. Please tell me some suggestions for moving forward with this application. If I go with a regular TPI replacement fuel pump and regulator I feel I’ll be pushing a lot of fuel back into the tank. Is this the way to go ? Or is there a simpler way to make this work. Thanks.

 

You need a sending unit without a fuel pump...

 

The amount of fuel you'll be pushing back to tank will be similar or the same, as the same pump hooked up to TPI; ...or less, since the the 383 should make more power (use more fuel), than the 305 TPI. Either way, in tank pumps were designed to pump fuel around in a circle for decades, and typically, they do that. In your case, you're actually reducing the burden on the pump dramatically, by running it a relatively low pressure.

OTOH, if you're dropping the tank anyway, you could easily at this point, put in a pick up and sock, then slap a mechanical pump on your engine (provided the block is drilled for the fuel pump push rod).

Which way seems more appealing to you?

 

A "standard" TPI pump can be used but a non-stock regulator will be required to reduce the pressure to the carb. The TPI regulator will maintain 38-45 PSI, which is likely to overwhelm the inlet needle and seat of any carb and cause severe flooding. 2-3 PSI is really all that is necessary.

Return fuel can recirculate to the tank, just as with the original TPI. Even a stock installation returns a lot of fuel to the tank since the pump will be moving its rated flow all the time, and at idle and low load the engine will be using very little of that. One advantage to this is that the lines will remain charged and the potential for vapor lock in the system is virtually eliminated.

An alternate would be to install a low-pressure pump in the tank, or a non-EFI fuel pickup in the tank and an external pump somewhere nearby. Those will still require a regulator and can get pretty noisy.