How to determine Power Valve
 

How do you determine the size of powervalve(s) to use? Im running a Holley 4010 with vac. secondaries. It has powervalves on the front and rear. It has no metering plates. I know that you need to know the vaccumn reading(s) to determine the size but which reading(s)? And isn't their a formula that you use with your reading(s) to get the correct size? Thoughts anyone:confused:

BH

You get your vacume reading at idle. The whole reason for the power valve is to give the engine more gas when it is under a load. You want the power valve to have a lower # than your reading so that it stays closed untill the throttle opens far enough or the engine comes under enough load to drop the vacume below the setting on the power valve. If you go too low than the engine will not have the fuel under load and if it opens too early you will have a real hard time getting the engine since it will always be too rich.

be sure your PVs are sized smaller than your lowest slow-idle in-gear loping idle vacuum reading.

Easiest way is to back boat in water and check it idling in gear on the trailer. Get a PV 1/2 - 1 point below your lowest reading..

Scott B

Ole smoggy transom :)

Scott: Shouldnt' I have it in the water:confused: I mean on the trailer in gear isn't near the load as in the water...Also how do you determine the secondary power valve???

Thanks
BH

In the water, idling on the trailer it is going nowhere, more resistance.. I was'nt clear on that I guess, sorry..

My secondary is the same as the primary on my SBC, tho I have been told to go one step higher by a friend recently.. It runs well, no smoggy transom, think I will leave it alone. Now my 454, thats a different animal. One day I will figure out that carb...

Scott B

Packing carb parts in a box, shipping them to the boat :eek:

Thanks Scott....I will get to the water probally Sunday (Sucks BIG TIME having to work Saturdays) :hothead: :hothead: So it probally won't be till next week to try out the changes (if any)

Randy
"Bad-Habit"