Packard Forum Index » V-8 (1955-56)

Nope, zero boost even up 4000 rpm. That's why I'm thinking that I need a smaller pulley.

Yup something isn't right. Where is the boost/vac gauge plumbed in? On the Avanti it's on the rear of the intake, I hear that if you tap in before the carb the numbers are generally higher.

I would look into changing the pulleys, maybe even going to the old style mac set up with two speeds. Just watch that you don't overspeed it!

I've tried the boost gauge directly off the supercharger, where the small port that I assume runs to the fuel pump (that's where it does on mine, anyway), then finally on the rear of the carb, where there's a large port for additional vacuum supply. It's on the opposite end where the vacuum line for the brake booster is. Keep in mind I'm using a 600 CFM Edelbrock, which isn't exactly the same as the AFB you have on your Avanti. The gauge seems to work, as it move from 20 inches of vacuum at idle to 0 under load and almost full throttle.

Yes, sounds like an issue with the pulley size. I'll be working on the Avanti later this week and try to get a better measurement on the crank pulley. Are you running the Stude style double belt pulley on the Paxton? I know it's not recommended to run them long with the hose disconnected, but does the blower seem to put out a good amount of air when you take the hose off and rev it a bit?

PS have you tried blowing into the hose to the gauge to make sure it does show boost?

Yeah, I'm using the double pulley on the Paxton, and yes, I pulled the hose off the air hat, and it does blow what to me seems like a lot. And yes, I blew on the boost gauge, it does work, but I can't attest to the accuracy of it. It reads vacuum rather well, though!