Pulley Swap and STILL 8psi! WTF???

[mcmmotorsports]

Hello all, I had 8 psi of boost on my '04 GT with a V-1 S-trim. I also have an Anderson Ford Powerpipe. I just went from a 3.6 Vortech Pulley to a 3.4 RR UltraGrip and I am still only seeing 8psi. Could it be a bad Bypass Valve? Or something else.
I have also been told it could be belt slip, but this is a brand new 108" Gates belt on a Reichard Racing Ultra Grip pulley so I thought belt slip should be no existent. There is a SLIGHT amount of belt dust on the back of the blower, could this be normal?
It is just strange that BOTH pulley's net the same result.

Thanks,
Michael

[Chuck]

I would suspect the bypass valve. What valve are you using? There are different bosch bypass valves that hold more boost than others. Do a search on this site and you should find alot of useful info.

[mcmmotorsports]

I would suspect the bypass valve. What valve are you using? There are different bosch bypass valves that hold more boost than others. Do a search on this site and you should find alot of useful info.

It is the stock Bypass valve that came with the Vortech kit. I would assume it is just a standard Bosch valve. I managed to squeeze almost 9 psi out of it today. But one thing I also noticed something else today, while the boost was climbing, it wasn't really smooth. I dunno, I am going to try a new valve first. If that doesn't fix it, then I will swap out the belt. I have a 108" Goodyear here, but I have been told I need a shorter belt with the 3.4 pulley. No one can give me a definate answer on belt sizes and it kinda twisting my nutz.

[92stanglx]

I beleive that you do need to change the belt when you go with a smaller pulley.

[mcmmotorsports]

I switched to a 107.5, I have a 3.2 pulley on the way, I probably will need a 107.3 with that.

[Goliath5.0]

Do the cheap fixes first, check the belt first.

Remember that a new belt will stretch!

-Chris