JETTING A 500 HOLLEY GPU

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GMAC 76
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JETTING A 500 HOLLEY GPU

Postby GMAC 76 » Mon Dec 10, 2012 2:37 pm

need some advice on jetting a 500 holley on a 220 gpu ,dual mags & high comp pistons.......current jets are #76's engine seems to be running rich (according to the spark plugs) wondering how far to go without getting to lean only jets i have on hand are 74,71 & 69's was hoping someone may have some first hand experience with this setup and could help me out.........running autolite 386 gapped at .024
Last edited by GMAC 76 on Mon Dec 10, 2012 2:58 pm, edited 1 time in total.

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PeaRiverOpossum
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Re: JETTING A 500 HOLLEY GPU

Postby PeaRiverOpossum » Mon Dec 10, 2012 2:49 pm

I was going through this same exact thing when I rebuilt mine. I searched on here and called everyone that I could think of and was told 74-76 jets. I just ordered a jet kit from summit and played around with them. I think I ended up using 76s. The kit is around $20 and would be a good investment vs. buying them individually. I am anxious to hear what others have to say. You may need to go with hotter plugs or re-gap...just guessing :dontknow: FYI....I think mine had 67s in it when I got it.

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John Fenner
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Re: JETTING A 500 HOLLEY GPU

Postby John Fenner » Mon Dec 10, 2012 3:25 pm

They typically come with 73 jets, get a power valve plug and block it off, you dont need it, I have 73s in my 220/470 convo.
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Re: JETTING A 500 HOLLEY GPU

Postby PeaRiverOpossum » Mon Dec 10, 2012 3:37 pm

John Fenner wrote:They typically come with 73 jets, get a power valve plug and block it off, you dont need it, I have 73s in my 220/470 convo.

John can you please give us a brief description on what the power valve actually does or doesn't do in this case?

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Re: JETTING A 500 HOLLEY GPU

Postby josh_2562 » Mon Dec 10, 2012 3:40 pm

What power valve are y'all running? If I remember right the auto lite are a black plug :scratch: when I tuned my gpu I used champion d16's they were easier to see the color on. It's been a few years but I think I used #76's

I got a holly 500 on a 0520 and I know it has #77 jets in it. Stock power valve

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Re: JETTING A 500 HOLLEY GPU

Postby PeaRiverOpossum » Mon Dec 10, 2012 4:07 pm

josh_2562 wrote:What power valve are y'all running? If I remember right the auto lite are a black plug :scratch: when I tuned my gpu I used champion d16's they were easier to see the color on. It's been a few years but I think I used #76's

I got a holly 500 on a 0520 and I know it has #77 jets in it. Stock power valve

it has been a while since I fooled with it but it seems like I'm running a 6.5 power valve

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JAMES
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Re: JETTING A 500 HOLLEY GPU

Postby JAMES » Mon Dec 10, 2012 7:18 pm

INCREASE JETS BY 2 SZ AT A TIME I RAN 78'S N MINE AND A 10.0 OR 10.5PV WHAT EVER IT IS AND RAN GET GET A BIG SQUIRTER 35+ GOOD LUCK DONT BLOCK THE POWER VALVE ITS THEIR FOR A REASON !!
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Re: JETTING A 500 HOLLEY GPU

Postby John Fenner » Mon Dec 10, 2012 11:20 pm

The power valve adds about 10% extra fuel under hard accelleration in a pickup truck application, towing or a hill run. Not needed in our application. You can easily bolt on a new two bbl 500 cfm carb and never have a problem running a GPU and a convo.the Cfm is comparable.
I never finish anyth,,,.


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