Shakey Boost gauge?
Thread Starter
Burning Brakes
Joined: Jun 2003
Posts: 1,022
Likes: 6
From: CT
Shakey Boost gauge?
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.
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.
Burning Brakes
Joined: Dec 2003
Posts: 1,004
Likes: 7
From: Adelaide South Australia
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.
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.
Thread Starter
Burning Brakes
Joined: Jun 2003
Posts: 1,022
Likes: 6
From: CT
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.
Good luck with it...roots blowers are loads o' fun 
