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I know the principal and function of the power valve. And I can see their purpose in a street driven engine. But in drag racing it's usually idle or WOT. So is there any reason to run or not run one?

Tim
 

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I know the principal and function of the power valve. And I can see their purpose in a street driven engine. But in drag racing it's usually idle or WOT. So is there any reason to run or not run one?

Tim
some feel that it's preferable to remove/plug the pv and square the carbs to get equal flow through all 8 barrels at wot. theoretically, midrange economy drops when the carbs are squared and no pv, but hard to say; you'd have to know what the a/f ratio is.
 

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some feel that it's preferable to remove/plug the pv and square the carbs to get equal flow through all 8 barrels at wot. theoretically, midrange economy drops when the carbs are squared and no pv, but hard to say; you'd have to know what the a/f ratio is.
I was told that if you do any cruising to go with a PV, for somthing that just idles and mash, no PV.

My 660's didnt have a PV, i just got a set of 750's with PV's from bigs performance. We'll see this year if i notice better gas milage and this year i have a bigger mill :)devil
 

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I was told that if you do any cruising to go with a PV, for somthing that just idles and mash, no PV.

My 660's didnt have a PV, i just got a set of 750's with PV's from bigs performance. We'll see this year if i notice better gas milage and this year i have a bigger mill :)devil
the thing is, with the carbs squared, they will theoretically be "fatter" at midrange without the p/v, in order to have a real good bsfc or a/f ratio at wot. for example, the standard specs on my 850s are 6.5 p/v, 82's primary, 88's secondary. with the p/v plugged, on the dyno we found that optimum wot performance (a/f, bsfc) was with 91s all the way around. i don't have any lean conditions between 3000-4000, and it runs just fine cruising it although i don't do that very much. the engine is relatively fuel efficient, considering what it is and what it's used for. i had carbs on it before that had p/v's, and there was a certain point around 32-3300 where it would lean and you could hear the detonation - went away at 3000 or 3400. plugs always looked just fine. if i had cared to address that, i probably would have gone with a lighter p/v, but never messed with 'em that much, just drove around it... so... with either combo, a lean condition at the carb transition is possible, so it's important to be listening/watching for it.
 
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