Holley Ultra HP fuel pump

[enkeivette]

So, I ordered the electric fans for my awkwardly placed intercooler, and now the only remaining problem with the vette is the fuel pump.

So, deciding that I didn't want to upgrade my electrical, there were really only two mech choices that will support my setup, the robbmc pump and the Holley ultra HP. Problem was, the Holley was a $500 pump :o

But I got lucky and I found a Holley alcohol pump on eBay for $200 bucks, and after finding that the gas pump and the alcohol pump share every part except for the diaphragm and spring, I bought the pump along with a gas spring/ diaphragm that I'm goin to swap out :D

So basically, got a $500 pump for about $250, and now my vette will stop melting pistons. Yay.

[94cobra69ss396]

Nice! Do you use a boost referenced regulator?

[joedls]

:bigthumbsup::bigthumbsup::bigthumbsup:

[enkeivette]

I probably won't have to, the pump is supposed to put out 8 to 9 psi at idle with the gas spring, whic would be perfect, so I'll only have to boost reference the pump itself :D

[94cobra69ss396]

How do you do that? A N/A carb'd engine needs 5-7 psi (I run the Chevelle at 6-6.5). With a boosted engine you have to increase the pressure equivalent to the amount of boost. At 10 psi of boost you'll need 15-17 psi of fuel pressue. I'm asking because for my next engine build I want to run a centrifugal on the Chevelle.

[joedls]

How do you do that? A N/A carb'd engine needs 5-7 psi (I run the Chevelle at 6-6.5). With a boosted engine you have to increase the pressure equivalent to the amount of boost. At 10 psi of boost you'll need 15-17 psi of fuel pressue. I'm asking because for my next engine build I want to run a centrifugal on the Chevelle.

Just to clarify, I don't believe this is required for a roots blower that is carbureted. I had my regulator set to 6.5 psi.

[94cobra69ss396]

That's because the roots is a draw through. The centrifugal is a blow through so if the fuel pressure is not increased with the boost then there won't be fuel flow.

[joedls]

That's because the roots is a draw through. The centrifugal is a blow through so if the fuel pressure is not increased with the boost then there won't be fuel flow.

Makes sense.

[enkeivette]

Not surprised someone asked, it more simple than you could imagine. The area behind the fuel pump diaphragm is ventilated to the atmosphere, to prevent pressure build up from changing the static pressure. So, when you run a vacuum-less boost line to it, it increases the pressure at the diaphragm.

It increases almost 1 to 1, someone did the math on it and it's actually like .97 to 1 or something, but it's pretty damn close. It only works to about ten psi, after that the fuel pump can't keep up. But with the intercooler now I should be maxing out at about 10 to 11 psi.

Also, demons like about 8 to 8.5 at idle, so it'll be right. And I'll be up at around 18 to 19 psi max boost.

[enkeivette]

You can actually blow into the line and watch the fuel pressure increase. It's pretty cool. My problem wasn't pressure before, it was volume.