Hi team, wondering what is the correct jet size for my 600 cfm Holley vacuum sec ? Motor is a 283 now 301 in my RPU. It is running a bit rich and yes I have got the floats right. Cheers, JW
What's the fuel pressure ? 5 to 6psi is a good pressure Stock jetting shouldn't be "too" rich. Maybe one or two steps. What power valve is in it ? Is the power valve in good shape (NOT leaking). One backfire will usually kill a power valve. Even the new carburetors with the check-ball "can" kill a power valve. Correct gasket for the particular power valve (there's two different designs). Mike
Its an older Carb from 83, I have had it stored away and all is good and as Holley built it. No leaks, runs real good, just a bit rich. Running a stock mechanical pump and no carb gaskets have been disturbed. JW
I'd try a pair of # 62 or # 64... Also use a vacuum gauge to dial in the idle mixure screws for the highest reading...
The jets in it are 66's and just checked the plugs, they are a nice light tan. Maybe things are all OK, was just expecting a little better in its economy being a very light car. JW
If you really want to dial it in the wideband O2 sensors have come down in price. With modern fuel the color is deceptive.
Nobody can tell you the correct jet number. It all depends on everything else in the engine, fuel, al***ude, and more. You have to tune to get the optimum number. Start with what Holley puts in there and play a few steps either side. Also tuning squirters, pump cam, idle mixture will have a lot of effect. There is not a number somebody can spout out that will be perfect for all combinations. SPark
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