Hi TimThe motor I used many years ago, came from Gillot with the Venturi the same size as the crank bore, I would at least start there.Les
Pressure tap can be 4-40 fox or K&B unit. Don't over tighten it or it will snap off. Use loctite and barely snug it. I've actually gone to a 6-32 nipple but with a restrictor in the line that has a #69 drill hole and is also a check valve. Side note the old KK check valves for 1/2a aren't big enough. Venturi? what venturi. Is it for upright cowled in or profile? Beyond a certain size there is no gain but you can go .440" if you have good height and shape to prevent the prop blast from blowing the fuel out. You're also dealing with centrifugal force slinging the fuel out on a profile. On my proto I have a .400" that's 3/8" above the crankcase. The choke is down by the spraybar and it has about 10-12 degree taper. I use 7075-T6 because the sections get pretty thin. Enough secrets for now lol. Motorman
Time just looking at some old notes and see where one of the fastest 21 SS had a 390 venture in it