Fuel Pressure
Burning Brakes
Joined: May 2008
Posts: 1,116
Likes: 5
From: Middleburg Florida
Burning Brakes
Joined: Jul 2009
Posts: 1,238
Likes: 288
From: ESCONDIDO CA
2025 C2 of the Year ('63 and '67) Finalist - Unmodified
C2 of Year Finalist (appearance mods) 2019
"Carb guys", like me, just like to farque around-its what we do.
Just let us be. And my "flow" is fine-its linoleum.
Just let us be. And my "flow" is fine-its linoleum.
Race Director
Joined: Jul 2001
Posts: 15,892
Likes: 42
Burning Brakes
Joined: Jun 2003
Posts: 1,022
Likes: 6
From: CT
I run a pro-systems 750cfm (custom built holley hp) and the carb builder said to make sure fuel pressure stays around 7-7.5psi throughout whole rpm range.
last year I had a 750cfm mighty demon carb with a 80gph mech pump and it made 7.5psi of fuel pressue at idle/cruise but would drop to 3-4psi at WOT. It made 327rwhp 380rwtq on chasis dyno. I swapped to a 110gph mech pump at the dyno shop and power went up to 365rwhp 410rwtq and fuel curve looked alot better. I still get a drop from 7.5psi down to 5psi... The dyno guy and carb guy told me i would make more power with bigger pump and holding 7.5psi. I'm swapping to an aeromotive electric pump and bigger feed lines soon and will be going back to dyno. I have a reg set for 7.5psi...i plan on adding 125hp shot of nitrous to my set up so I have upgrade fuel system anyway.
last year I had a 750cfm mighty demon carb with a 80gph mech pump and it made 7.5psi of fuel pressue at idle/cruise but would drop to 3-4psi at WOT. It made 327rwhp 380rwtq on chasis dyno. I swapped to a 110gph mech pump at the dyno shop and power went up to 365rwhp 410rwtq and fuel curve looked alot better. I still get a drop from 7.5psi down to 5psi... The dyno guy and carb guy told me i would make more power with bigger pump and holding 7.5psi. I'm swapping to an aeromotive electric pump and bigger feed lines soon and will be going back to dyno. I have a reg set for 7.5psi...i plan on adding 125hp shot of nitrous to my set up so I have upgrade fuel system anyway.
Last edited by L-82kid; Jun 21, 2011 at 12:59 AM.
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Pro
Joined: Aug 2010
Posts: 698
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From: Stockholm Sweden
What carb do you run?
For my Holley the recomendation is between 5 and 7 psi.
At ALL times (from idle to WOT).
If you have a higher pressure there is a risk of the fuelpressure pushing down the needlevalves/floats and the carb is flooding.
//Ricky.
For my Holley the recomendation is between 5 and 7 psi.
At ALL times (from idle to WOT).
If you have a higher pressure there is a risk of the fuelpressure pushing down the needlevalves/floats and the carb is flooding.
//Ricky.
Race Director
Joined: Jul 2001
Posts: 15,892
Likes: 42
last year I had a 750cfm mighty demon carb with a 80gph mech pump and it made 7.5psi of fuel pressue at idle/cruise but would drop to 3-4psi at WOT. It made 327rwhp 380rwtq on chasis dyno. I swapped to a 110gph mech pump at the dyno shop and power went up to 365rwhp 410rwtq and fuel curve looked alot better. I still get a drop from 7.5psi down to 5psi... The dyno guy and carb guy told me i would make more power with bigger pump and holding 7.5psi.
Burning Brakes
Joined: Jun 2003
Posts: 1,022
Likes: 6
From: CT
Race Director
Joined: Jul 2001
Posts: 15,892
Likes: 42
high pressure ' pumps are not.If two pumps have the same flow capacity but the 'performance ' version simply does it at higher pressure, nothing is gained.
