What sized powervalves should I be running? Currently I am running two Holley 750's HP's with 6.5 valves. The motor is a 468, 10.5-1, Weiand Tunnel, Rec. Port Heads. The reason I am asking is because I was told to drop down to 2.5 P.valves due to the vacuum with a tunnelram causing it to dump fuel at an idle. My concern is the possibility of the motor running too lean. Thanks for the help!
I have heard that the size of your powervalve can be calculated through this formula.Hook up a vacuum guage on your engine and measure it at idle then divide this number by 2 and that's your number.13 inches=6.5 power valve and so on.Maybe someone could correct me if I'm wrong and maybe it's different with dual 4's.If so I'd like to know.....
If this is a jet boat, put a vacuum gauge on it and record your vacuum at wot, then back it down 500 rpm and record the vac and put a valve in that matches that rpm/vac reading this will bring the power valve in on the top end as jet boats need more fuel at top end due to the increase in load. You will not add fuel at idle unless the diapham is broken as the pv only enrichens the main circuit.
The standard way to select the proper power valve can be found right here.
Holley
Racing Ray:
The standard way to select the proper power valve can be found right here.
Holley Now all we need is 058 in here, dont forget bout the low pressure area too.
What do you drag race Ray?
elimination:
What sized powervalves should I be running? Currently I am running two Holley 750's HP's with 6.5 valves. The motor is a 468, 10.5-1, Weiand Tunnel, Rec. Port Heads. The reason I am asking is because I was told to drop down to 2.5 P.valves due to the vacuum with a tunnelram causing it to dump fuel at an idle. My concern is the possibility of the motor running too lean. Thanks for the help! You're right. Most set-ups like yours only need 2.5 or none at all. Consider just blocking them off and jetting up 3-4 sizes to compensate for the lean condition.
~Ty
Blown 472
Now all we need is 058 in here, dont forget bout the low pressure area too.
What do you drag race Ray?
66 Chevelle S/C S/G
That low pressure area is pretty wicked. eek!
Ty
Help me understand why a Jet application is so much different. I am trying to learn here too.
[ July 09, 2003, 07:23 AM: Message edited by: Racing Ray ]
WHat are you running in that car?? Super gas??
I was talking about the jet aplication, due to the load increasing on the motor from the rpm increase I was told it is best to add fuel to the motor rather than lean in out on top end like a prop boat, and the powervalves can be used as a switch to do this. It is easy to map the rpm to vac chart and then pick where you want to add fuel.
The car is capable of and I am licensed to compete in Super Comp and Super Gas but running a door car in S/C is tough so I pretty much stay in Gas. I understood your post and what you were saying about trying to enrich at a certain RPM band. I was asking Ty why you would size a power valve so small or remove it and go up only jet 4 sizes which to me appears would cause a severe lean condition on the top end.
Racing Ray:
The car is capable of and I am licensed to compete in Super Comp and Super Gas but running a door car in S/C is tough so I pretty much stay in Gas. I understood your post and what you were saying about trying to enrich at a certain RPM band. I was asking Ty why you would size a power valve so small or remove it and go up only jet 4 sizes which to me appears would cause a severe lean condition on the top end. Gotcha, tube chassis car?? what engine you running?? I used to work at Ken Thurm race cars and we ran a s/c camero.
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