Holley Power Valve Selection
 

Hey Guys. I'm finally getting down to the wire on getting the boat ready. I have mixture problems with my holley 4150's. The first place I'm going to start is replacing the power valves. I rebuilt the engines so I don't know if the valves in it are not sized right or blown. But I'm going to replace anyway. I put the vac gauge on them today and I get a soild 15" at about 600 RPM. At I higher idle of about 1000 I go up to 20". Where should I size the valve. Should I put in a 7.5 for the 15" or a 10.5 for the 20". Thanks for the advice. Hopefully I'll get the boat out next weekend.

Jeff

I have about the same vacume and I run a 6.5 in the front. Its really a matter of trying it out and seeing if it runs well though. Every motor is different.

You should check your vacuum readings when you are running, check your readings at your normal cruise speed. Then install a power valve with a lower opening value so your not using excess fuel while cruising. A good guess is between 5 and 7.5. But this depends on your load and prop pitch. A 10 is to high..

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