B.Buster

iTrader: (1)

I had 7#s boost originaly.Changed from A4 to m6.With A4 and converter I had higher RPMs (4500-6000 shift).With M6 my boost dropped to about 5#s I figure because RPMs building slower.Then I upgraded my valve springs and went to 1.8 ratio rockers. Now my boost dropped to 4#. I checked my belt and tightened it a bit. I have the 6 rib 4in pulley that came with D1SC. What pulley should I go ? Thanks.

EPP

iTrader: (22)

I don't see why the change in transmissions would of changed the boost. 6000 rpm is 6000 rpm, no matter if you get to it later or not, the blower is still going to basically see the same boost level once it is there. Back in the day I had a D-1SC 6 rib with the same 4.0 pulley on my '02 Z28 with a six speed, with headers an no cats and a Hooker cat back. It made 7 psi of boost at 6000 rpm.
Make sure you truly do not have just a slipping blower belt. Clean the blower housing off and keep tabs on it to see if you see any black powder on it. Once a belt has slipped, it is more prone to slipping as it gets glazed over. A new belt will stretch and will need to be retightened after the first half an hour to an hour of use.
The bypass valve can be removed from the system for several runs as well, just to make sure it is not the problem.
If the above items don't help I'd be looking for a boost leak. You can take your intercooler hose off at the blower, and cap the end of it. Do the same up at the throttle body but have a schrader valve installed in it so you can add pressurized air. Doing this will let you know if you have a boost leak in the system. Keep in mind you can also have a leak in the intake manifold. The LS1/LS6 intakes really aren't known for this but it can happen. Bob

B.Buster

iTrader: (1)

Thanks Bob, I did look for black dust and had very small amount. I will change belt anyway (have spare on hand) and check after retighten. Won't be able to test run as rain and snow are moving into the area. My car has never seen either. BTW what size pulleys are available (6 rib) less then 4 in.

Packy

iTrader: (11)

+1 for the tranny comment. I went from a M6 to an A3 and never had any boost issues. My boost builds about the same as far as I know. I know it peaks at the same level.

B.Buster

iTrader: (1)

thanks Packy

EPP

iTrader: (22)

Increments on down to something like (no coffee yet...) a 3.20 or 3.25. Bob

B.Buster

iTrader: (1)

Thanks Bob, I took a good look at belt while up on my lift. Only had a 2K miles on that belt. I will be changing belt today but will not be able to test for days because of snow. Even if this works I'm going to upgrade to an 8 rib setup with better tensioner and 8.5#s boost. Any ideas ?

EPP

iTrader: (22)

After you swap over to the eight rib assembly with the larger 7.65 crank pulley, a 4.25 blower pulley will probably be the one for your combination. Bob