I have built a 272 CI Flathead for my F-1 with the following mod’s; Max-1 cam, (new) 8.5:1 heads, ported, Red’s tube headers with dual exhaust, Chevy distributor (By Charley) with mechanical advance only. For the first 500-ish miles I am going to be using a Holley 94/2100 (the one with 1.25” Throttle blades). I’m trying to get the tune as close as I can before the first start and about all that’s left to think about is Jets and Power Valve. I would think that the Max-1 cam would result in a lower vacuum which would affect both jets an PV. I know that it is fairly common to remove the PV and upsize the Jets. When/why is that done and if I did remove the PV then what Jets should I start with? If I keep the PV then what size Jets and PV would be the best place to start? The 2100 currently has 51 Jets and a 758 PV. I ordered a PV plug from Speedway so as to have it on hand should it prove best to eliminate it. Suggestions?
With just one carburetor, I would use a power valve. With the big lumpy cam, I would start out with a power valve that opens at 6 in of vacuum, but once the engine is up and running you can fine-tune that. You want the power valve to stay closed at idle. So you'll need to take your vacuum reading at idle and then use the power valve that is somewhat less than that.
When I put aMAX-1 in a fresh 258" flathead, I was surprised at the amount of vacuum it held. Around 20 at idle if I remember correctly. I have come to the conclusion that they are pretty mild.
You are probably aware, but make sure the PV you buy is the older style for the 94 and not the one for the newer Holley carbs. The sealing seat is different.
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