Holley double pumper jetting help
 

Hey guys, im putting together an old Banana 24 on a budget. I'm running a bone stock Chevy 454 with a Davis (D.U.I) ignition and Stainless Marine manifolds. The only carb i have is an 850cfm Holly marine double pumper. Its a little big i know but its all i have at the moment. Stock jetting that comes with this carb is 88 primaries and 96 secondaries. Anyone want to guess where i need to be for jetting? Can i jet down an 850 enough to run well? I havent hit the water yet but i'd like to be close when i go out on saturday!

Thanks!

I would try it the way it is first. Google how to read spark plugs with unleaded fuel to know exactly what to look for. Basically, get it to operating temp. Put a new plug in. Take it up to 2500 rpm's ( on the water and under load ) to get it off the idle circuit or more but don't open the secondary's. Take a 2-5 mile run and shut it off immediately. Pull that plug and look at the ring. That will tell your the mixture. As long as the plug / ring isn't black, put another new plug in and floor it for as long as you are conformable. Shut it down without idling again and pull the plug. Read again. now you have secondary info. Simple hey?

"Jetting down" may not be required. The smaller a carb is, the less "help" the fuel needs to be pulled into atomization.

The stronger the signal across the carb is, the smaller the jets need to be for a given engine.
What that means, is that since your carb is pretty much oversized for your engine (weakening the signal across the carb) you should stay fat on the jets until you test and tune.

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if i was RIVERRAT id say +100