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Old 06-11-2024, 02:16 PM
nalvarez nalvarez is offline
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Join Date: Jan 2024
Posts: 40
Default Help with Jetting

Hello, I am new to the hobby and looking for some direction on how to get started tuning my carb. I have a pontiac 428 with a Holley 750 4779. The carb has had the choke horn milled off. It has Doug's headers, edelbrock aluminum heads, and this CAM

The carb was freshly rebuilt by a reputable shop, but it's still not running right. It cranks right up, but dies right away unless I hold the gas pedal until it warms up a bit. Once warmed up it will idle fine. It bogs off of idle and seems low on power. Sometimes when its fully warmed up it doesn't want to re-start. Plugs look pretty black and I have a feeling its running rich. The exhaust is pretty strong and burns my eyes.

I have adjusted the 4 corner idle to the highest vacuum, although the vacuum is pretty weak. I'm assuming it's due to the cam.

Im looking for suggestions on which jets would be a good place to start with for my setup. I havent pulled the carb yet to see what's installed on the secondary side, but I took a peek at the primary side. There are 77 jets in there now with no power-valve, just a plug. Im wondering if I should install a power valve and jet down a few sizes. The accelerator pump nozzles look to be #25, they are hard to read so not 100% positive on that.

The car will not be tracked and will be used mostly for cruising.

Thoughts?


Last edited by nalvarez; 06-11-2024 at 03:15 PM.