Hi all. I need to know a good starting point for the jet size on my carb. It's a holley 750cfm vacuum secondary dual feed fuel line, but non-double pumper. It's going on a 355 with trick flow heads, a 224, 230 @ .50 cam, and a performaer RPM air gap manifold. Has headers and exhaust as well. I'm expecting 400 or so HP out of the motor at the flywheel. Carbs are new to me and I just need somewhere to start with and tinker with from there. I eventually want to go to a non-vacuum secondary double pumper carb in the future, but I'm trying to get it going with this one for now. Any help or info I can get, I'll take.

Bolt it on and see how it runs with stock jetting. Go from there.

Most likely this is a 4160 style carb with secondary metering plate instead of secondary jets, correct?

Yep, believe thats the one. My bro bought it originally and I couldn't find any part numbers on it anywhere. It only has idle mixture screws on the front facing bowl.....elec choke...basically an off the shelf auto zone carb i think.

The part number is the "List" number stamped on the front left corner of the choke tower.

it says 80508-3 and right under that, 1216. Hope that means something.

The 80508 does. It's a 4160 model 750 CFM vacuum secondary. Metering plate on the secondaries. Came with 72 jets in the primaries and 6.5 power valve stock. That would be a good place to start if it's been modified from there. It had a .025 accelerator pump squirter, going up to a .028 might help out. The secondary spring was plain, a Quick Fuel Technologies adjustable secondary housing is a very good upgrade for a VS carb.

Wow, thats some really helpful info. Now at least I know what I have. I'm hoping to have everything together and running this weekend, so I can see how it goes and post my progress back up. Thanks!