do your engines have innercoolers and how much boost are you running?

Yes we ran the chillers. Boost is 6lbs (flirts with 7 at max rpm)

3.5 in of vacuum seems low,what are you running for cams?

Wasn't tryin to be a dik, it's just that Dan, the original poster, has been having issues with the boat since he got it in the water. I've been trying to help him get it running better. He's getting all kinds of suggestions from several different people. He's new to carbs, and is trying to learn. So i don't want to see him getting confused.

Idle vacuum has no bearing on a non boost referenced roots blown setup. And chances are with a 2.5 powervalve on HIS setup, will potentially melt pistons.

My engines don't foul plugs, don't backfire , idle all day, and have a good fuel curve on the AFR meter. I also have 420 blowers and non boost referenced carbs.

What kind of speeds you gettin out of it? What drives? Looks like a nice gun

Custom Madera Cams. Bob made them for 10lbs of boost, we didn't feel like spinning these baby blowers that hard. Had to run 22% OD to get what we have.

I understand you have to tune for a part throttle lean issue, but what keeps the plugs from fouling out if the Power Valve is wide open at idle? Not trying to be a dick either. Joe at Fast Forward tuned mine engines on the dyno.

Only ran it in flat lake water so far. It is right at 90mph. Konrad PRS III Drives

The engines aren't fouling plugs at idle. The problem was the carbs had 86 jets in the primary, 96 in secondaries WITH a powervalve in the secondary. So I was like havin 86/106 jets. It went waaaay rich as soon as the secondaries opened. I simply plugged the rear pv's and we went for a ride.

It's not opening at idle. If it was we'd see fuel dripping from the boosters at idle.

Good numbers . Wait till you get it in some chop!

Mid 90's easy