losing manifold pressure at altitude

[GearUp]

Tracking down a very similar problem myself. One of the guys at Main Turbo suggested it's best to remove the spark plug from one cylinder, rotate the crank to open the valve on that cylinder, then use a compression tester to pressurize the cylinder and the intake or exhaust (whichever valve you opened). You'd also need to plug up the exhaust pipe at the end, or the intake at the air filter or inlet of the turbo. If you're looking at the intake side, you can also watch the MAP gauge.

I haven't done it yet, but love the high density foam plug suggestion. Thanks Joes.

[Dan schultz]

I had the same problem with the ball joints on my new exhaust from Acorn, had to send both back for re-work. I eliminated the springs and I am using titanium bolts and 12 point nuts was the only way that I could get them to seal to my satisfaction.
It does hold 75% power to 18k.

Dan
67S P337-0168