L-82kid

I have a 144 blower on a 350 and it has 7.5psi pullies. I noticed the other day when I downshifted 4th-3rd and hit WOT that the boost gauge needle was bouncing and didnt go up smooth, if was jumping 3psi in both directions. The needle was jumping until i let off throttle. I checked it again from a 1st and 2nd gear pull and it stayed steady and seemed normal. I did notice that it doesnt always show 7.5psi sometimes it only makes 5psi of boost at WOT. I run hard line to gauge and dont see any leaks at connections?

Could this be caused by supercharger belt slipping? Would a low fuel pressure problem cause this as well? I make 8-9psi of fuel pressue at idle and cruise but noticed sometimes it drops to 4psi at WOT! it seems to happen when I go WOT from 3rd and 4th gear rolls when on highway. Car runs good in lower gears though. Maybe I need to upgrade sender, fuel lines, and pump size.

OzzyTom

If you can not find a simple fault which is causing the fluctuations (leak, slippage etc) here is a potential area to investigate ...

I have a turbo-charged application in another car.
I had issues during the development phase at pressures over 10 psi .
Could not maintain constant boost due to insufficient valve spring pressure. Replaced all the inlet valve springs and solved fluctuating boost issue.
I now run up to 16 psi.

L-82kid

I'll called the Holley/weiand tech line today and the guy seems to think that its belt slip that is causing the problem. I ordered a new 10rib from fleet pride and will try it tomorrow. Still need to upgrade my fuel set up.

yellow 72

If you have time to look at the boost guage, you need a bigger blower..
I joke Good luck with it...roots blowers are loads o' fun