Thread: alittle guidance appreciated on 850 holley

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your intake as no vacuum ports .what did the engine have for vacuum in gear at idle with old carb ? then that would be were you could start i cut the reading in 1/2 so lets say you had 8 inchs of vacuum in gear i used a 4. or4.5 power valve if less then 3 inchs at idle i plug them then jump up on jets size so if you plug the power valves in the new carb any were from 90 to 94 i would start on the smaller size jets.if race stuff i just plug the power valves

Thanks pat. I have never checked vacuum with old carb. But I will before I remove it. This motor is just for mud bogging and ridding trails in the woods. I am running a manual trans. I try to do as much research as possible le before asking questions and more times than not it will redirect me to a post on this forum so I figured it has to be a good spot to ask questions. Will the power valve plug out of my older 750 holley double pumper work with this new 850 ultra hp?

Originally Posted by 505onrocks

Thanks pat. I have never checked vacuum with old carb. But I will before I remove it. This motor is just for mud bogging and ridding trails in the woods. I am running a manual trans. So I would check my vacuum in neutral correct. I try to do as much research as possible le before asking questions and more times than not it will redirect me to a post on this forum so I figured it has to be a good spot to ask questions. Will the power valve plug out of my older 750 holley double pumper work with this new 850 ultra hp?

yep your power plugs will work in the new carb how big is the cam at 050 . if you had power plugs in it before then you may have low vacuum ? what ever you have at idle i have aways drop down under max vacuum at idle on power valve size by 1/2

Thanks again pat. I do not know the specs on this cam. I destoyed my first 505 that I knew all the specs on and had dynoed. I bought this engine already assembled from a friend. Im not sure if i know what you mean by how big is my cam at 050. ? If that means duration@ .050 I think i am around 262/273.

if that big @050 on dur i would go to just power valve plugs