Ive got a iron block 408, callies rotating assembly, diamond boost pistons, Trik Flow 225 heads, LS6 intake, stock TB. F1A with 4.0 pulley, stock size crank with Aster Bracket.

Im only seeing around 10-12PSI at 6k RPM and then it drops. Ive talked to Bob, and a few other people and they all have agreed its low. Ive checked, double, and triple checked for leaks and found ONE tiny but that didn't fix the problem.

What is something I can do to try and find out the problem?

 

i just went through a bunch of issues this year when i went to a fmic and enclosed race valve .

I had two main issues , i had a hole in my fmic , then after many days and checking it turned out i also had an issue with my enclosed race valve , i didnt have a good vacuum/boost source. SO i added a t into the brake booster hose and everything was good them there.

Also what i did to make sure i had no leaks was go to home depot and made some boost testers for my 3" piping .




what size crank pulley are you using , i assume the 7.65 from procharger ??


Also if you see that much boost and then it drops that makes me think belt slip, or a coupler is torn or ripped or blew out and only opens at that boost level .

I would check from the pc outlet to the tb and see if you can find any leaks .

 

I found a leak. The connector from the pipe to throttle body. Fixed that, now I'm seeing 12psi max all the way to 6900. This is still super low, I should be closer to 17-19 from what I'm being told by ATI and several other knowledgable guys. I've had problems with this head unit and had to send it back once. Could something still be wrong with it?

7.65 crank pulley. Yes. I ordered a 3.8 pulley to see if this helps me get to my goal