On my sn2000 I just put new races, impeller shaft and balls in it. Now it hits 5psi and drops to vacuum on the gauge. Do I need to reshim it when going to new races? Before I was seeing 7-8 psi at the manifold...
On my sn2000 I just put new races, impeller shaft and balls in it. Now it hits 5psi and drops to vacuum on the gauge. Do I need to reshim it when going to new races? Before I was seeing 7-8 psi at the manifold...
5psi is normal for an SN unit. Do you have the upgraded or the stock impeller?
Michael
www.superchargerhelp.com
Originally Posted by Michael
Upgraded. Even if it stayed at 5psi I wouldn't mind but it literally falls back to no boost afterwards. Even when it was whining before I took it apart it was making more boost than that on the gauge and didn't just drop off(I am not even going to 5k rpms when this happens). Is this indicative of not enough pressure on the balls?
OK so with an upgraded impeller, then you should see more than 5psi.
But the falling off is more than likely due to the balls slipping at high boost. I think you're diagnosis is correct - you may need to reshim.
Michael
www.superchargerhelp.com
How much ballpressure do you have ?So how much force to turn the pulley ?
Do you have beltslip ? check for black pouder around the sc pulley.
All rubber hoses tight ?
Greets, Marco
'91 Chevy 496SS, Edelbrock Pro-flo 2 injection, alu. GMPP heads, blowercam, coolmist water injection, turbo in the works.
*VIDEO* http://www.youtube.com/watch?v=6ZOdXg0TOdw
I have checked both the belt and the hoses. Everything looks fine.
The pulley feels like it is a little light to turn. I am thinking I don't have enough ball pressure. I am going to call craig and get some shims sent to me.
Don't think, but measure.
Use a torque wrench, it should take between 28 lbs/f and 35 lbs/f to turn the pulley.
I and others have found out that tightning the frontcase cover bolts also tightens the ball pressure.
Greets, Marco
'91 Chevy 496SS, Edelbrock Pro-flo 2 injection, alu. GMPP heads, blowercam, coolmist water injection, turbo in the works.
It does sound like your lite on the ball pressure.
Talked to craig and he agreed. Got some shims on the way.:)
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