The V8 Owners Forum -

Hi guys, just wondering what fuel pressure I should run my holley at? basicaly I'm going to be running an injection pump which is the setup I was running with my old engine, andthen fitting a pressure reg to drop the pressure down for use with a carb, but how low do I need to drop it?

Cheers
Jono

Hi
normally 5 to 7 PSI for a carb, though it should work fine with the injection pump, I would be concerned about long term reliability of the pump when it is running so far from it's designed operating pressure. Short term fine long term a bit of a bodge and it would be better to get a pump designed to operate in this pressure range.
Best regards
Mike

I'd say the injection pump will be ok provided it runs all the time and returns spare fuel to the tank as normal, and the reg taps fuel off this line, rather than attempt to reduce the pressure of that entire circuit.

cool.... yea the reg will have a high pressure side from the pump, a return to the tank for un needed fuel, and a low pressure outlet for the carb.

Cheers
Jono

What flow would a carbed RV8 need at 7-8psi?
Can the injection pump flow that much?
What injection pump do you have?
I would do a search and find the flow/pressure graph for your pump and check that the flow for your pump looks in the ball park for your carb requirements?

A quick google and it looks like most carb pumps flow 80 - 100+ gph, comparing that to the bosch 044 which is quite a monster of an inj fuel pump would flow about 5LPM at 1 bar which is 66GPH. More mundane bosch pumps are more like 4LPM flow which is 53GPH! so from that I don't think it will work!

Certainly do some calcs before starting!

Tom.

done a quick look, and the facet red top pump flows 151 lph
compaired to the FD3s pump I'm running flowing 163,
but to be honest I'm looking for the cheepest way around the problem.... if I can get a solid state pump to do the job cheeper than the regulator, then I'll be going down that route

Jono