holley 650 jetting
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Joined: Apr 2007
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holley 650 jetting
so i bought a new 650dp for my truck and i'm having a tough time jetting it. the factory jets were 67 and 73 well that combo was way to lean, the plugs came out really white so i went up a few and it was still really lean well i'm at 74 front and 80 in the back and its still lean not real lean but still not leaving a nice brown color on the plugs so my question is should i keep going up or is it something else? it idles nice and runs pretty good, heres my combo its a 351m .030 over with a edelbrock performer 400 intake with a comp cams 268h cam and a set of 1 3/4" long tube headers to an x pipe with duel 2 1/4 flowmasters timing is 16* and 34* total with no vacuum advance, i have checked for manifold leaks at least 3 time and nothing so i'm kinda stumped any input would be awesome!! thanks!
Post Fiend
Joined: Oct 2003
Posts: 9,176
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From: Western Central NV
How long are you running the engine between plug checks? What is your fuel pressure @ the carb? I run a 4160 600CFM on a 460 with an Edelbrock Performer & the Cam advanced 4 degrees past TDC. with 2.5"duals into a set of Summit Turbos.
I run #.062 on the primaries. secondaries are the plate that came with the carb. The carb came with .064.
I think .074 are too much. I think you need to look at fuel volume & pressure, & or vacuum leaks. If you step up to much bigger jets you will be able to run alcohol.
Craig
I run #.062 on the primaries. secondaries are the plate that came with the carb. The carb came with .064.
I think .074 are too much. I think you need to look at fuel volume & pressure, & or vacuum leaks. If you step up to much bigger jets you will be able to run alcohol.
Craig
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Joined: Nov 2003
Posts: 778
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From: southeast Idaho
What is the list # on the carb? Lets check and see what it's supposed to have as far as jets and power valves and such. I quit buying carbs from local parts houses as it seemed someone had usually had their fingers in them prior to being sold to me anyway.
Elder User
Joined: Nov 2003
Posts: 778
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From: southeast Idaho
Looks like there is 5 different ones, 4777 then 4777-1thru 4 Yours had 67 and 73 would be right for a 3 or 4.. w/65 power valve Have you checked the power valve? might be a bad one or somethings not letting it open for you. Definately be lean if that doesn't open. Might just be a wrong power valve also. If you can check your vacuum Holley says divide that by 2 and use that number power valve, if you run 15 inches at idle in gear, use a 7.5
the more I think on it you need to check the power valve and make sure the right ones in there... or somethings plugged that shouln't be, might not happen often but it does happen on new stuff
The others had a 71-76 jet setup, and the #1 and 2 had 67-76 jets in them they all had 65 power valves in them too 6.5
the more I think on it you need to check the power valve and make sure the right ones in there... or somethings plugged that shouln't be, might not happen often but it does happen on new stuff
The others had a 71-76 jet setup, and the #1 and 2 had 67-76 jets in them they all had 65 power valves in them too 6.5
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