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Old 06-28-2017, 08:11 PM   #1
JL8Jeff
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Join Date: Aug 2004
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Holley 600 carb jetting

I'm wondering how much I need to go up on the primary jets on the Holley 600 vac secondary carb that is on the ZZ3 motor in my jet boat. I did a quick run yesterday and had a bad stumble off idle and found it has .025 pump nozzle which seems way too small so I'll try .031 and then .035 if necessary. The carb has 66 primary jets and I'm not sure what the rear plate is until I can open it up again but it says it has the silver spring in the vacuum secondary. Here are the plugs which look pretty lean but I think they are platinum and only 1 of them had the bottom puck left on it so most of them were .050 or larger gap. I just put the recommended AC MR43LTS plugs in gapped closer to .042 like stock. The distributor is a MSD street unit with no vacuum advance connected. I can't get the engine to idle with the open headers so I can't verify the timing right now. I have some 72 jets but I'm thinking I should try 68 or 70 first to see how the plugs look.



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