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Josh Kurtz
09-09-2004, 08:53 PM
Ever since my "performance" rebuild, my 87 GN will not build boost on the line. Previously, when the car was stock I ran 12.7's at 105 launching w/ 10lbs of boost, 16lbs full boost. Now, I hold the brake before I leave the line and can't build 2lbs of boost if I'm lucky! Now I ran 13.6 at 108 with 2.6 60' :( Still runnning stock headers and cross over pipe, stock injectors, intercooler and turbo (now ported), Red Armstrong 93 chip, and adj. fuel press. reg. The rebuild consisted of .020" over forged pistons, ported heads and intake, Crane or Comp cam (I wish I knew and had the specs), 3" Houston downpipe, "orange stripe" torque converter. I checked and made sure the enlarged wastegate hole is sealing. I can disconnect the wastegate actuator and wire the wastegate closed and still can't build boost while holding the brake and pressing the throttle- even floored! Could a small exhaust leak do this? Sorry for writing a book! Please help! :banghead: Thanks, Josh

Keller
09-10-2004, 02:28 AM
Could a small exhaust leak do this?

YES! And a large leak will do it worse. :D

You are making more power...as evidenced by your MPH increase. But you can't spool. And that indicates a leak possibility to me. Intake or exhaust air are both possible. Could be at the headers, crossover, intercooler hoses, or (more likely) downpipe/puck mating surfaces. At speed, the flow is so huge that a small leak isn't as noticeable. But at the line, everything makes a big difference.

Since you are having such trouble spooling, but its OK down-track, my guess is the puck alignment. Might have to take the turbo exhaust housing and downpipe off and massage the two's fittment slightly to get them to play well together.

Josh Kurtz
09-21-2004, 08:33 PM
Well, looks like an exhaust leak was the problem; and not a small one either! The black carbon deposits on the outside of the spark plug boots was a give-away that the problem was at the header on the passenger side. After removing the header, I found the obvious culprit- no header gasket or header to turbo gasket :nono: Each exhaust port was leaking the whole way around, and the header to turbo flange was leaking between each bolt. New gaskets and a couple hours later, the 'ol GN was back to how it should be! The turbo spools up much quicker, and builds boost quick when I two-foot it. I thought of calling the guy who built my engine and giving him an earful, but I don't think I ever want to see him or talk to him again (unless he wants to give me some $ back) Wonder if there's even forged pistons in there?... Thanks for the help. It's much appreciated!

Turbo2nr
09-22-2004, 07:00 AM
sounds like a pain in the butt, but you could take off your turbine housing and DP and reattach them together off of the car. Look thru the turbing housing while shining a light in the other end of DP. See any light? Or use a marking powder to get a mark of where puck hits the waste gate hole. Adding a gasket between the DP and turbo will move the puck a little. I think that is your problem, or an exaust leak.

Keller
09-22-2004, 10:43 AM
...no header gasket or header to turbo gasket. Each exhaust port was leaking the whole way around, and the header to turbo flange was leaking between each bolt...

With the stock headers, there are no factory gaskets from the heads to the headers. Using them may be fine, but just a small but of high temp O2 safe sealant usually is all that is needed. Copper gaskets (like ATR makes, for instance)should work great, but you may want to periodically check their torque to insure sealing. I wouldn't use gaskets meant for a normally aspirated car.

The afternarket gasket to the turbo (again, I'm aware of one from ATR) is a nice piece and I use one.