Power valve and jets
 

We just rebuilt my carbs, they are Holley 850's. What power valves should be used in these carbs. The carbs are on 454 425hp chevy crate motors. Also what jets should be in them, right now they have 96's all the way around.

What model # are the carbs ? Its on the front right side of the choke tower. Generally...you should have a 125-65 power valve. I'd say (just my opinion) that the 96 jets are a little big. What intake are you running ? I'd prolly square jet it with 86's and read the plugs. As an all around easy way to get it real close...we run ours and keep track of the mph. Keep increasing jet sizes till the mph drops off...then back up 2 jet numbers. :drink:

The carbs are 80443's.

In my Merc manual it calls for 84's all the way around for the 850 on 440/460 cyclones.

The only number on the power valves in the rebuild kit is a 6 and I can't remember what the original had on it but the original is what we left in it.

Both carbs were very dirty(the boat had been sitting for years I was told when I got it). The problem I was having before the rebuild was that the engines idled between 1000 and 1300 all the time and had to run for a long time before they would run when shifting into gear. The hydraulic steering and tie bars on the transom was also black from the exhaust blowing on it.

This is what the Holley tech site says should be in it.
80443 850 (F)88,(R)96 6.5,6.5 4150 Marine

These are the power valves you need.
http://www.summitracing.com/parts/HLY-125-165/

The transom was black from the carbs most likely being too rich. You could leave the 96's in the back if you want..but I'd lower the fronts down. That'll prolly clear up the over rich condition at idle. Also...make sure the air bleeds are clean (gently blow them out).

This info should get you close sir. :drink:

The Holley site only says power valve. It doesn't say whether it's primary, secondary or both. I'm going to go out on a limb and say it's primary because of the big difference in jet sizes. A power valve is usually equal to 6-8 jet sizes of added fuel.

The only numbers on the power valves that came in the kit is a six, there is also a k do you think they are the 6.5's?

These are both 6.5's. Yours look like this sir ?