Thread: Top swap not making power! Help

I did a gen 3 top swap on my 2000 grand Prix with an xp cam and all the little things to go with it. Lifters. Valve springs. Ported heads. 42.5 lb injectors. Also on a 3.4" pulley. Its on the dyno and everything is reading good except for the power. Its only making 190 something horse to the wheels and a peak of 4.something boost. Timing is at 15 degrees with 0 knock. The boost reading was choppy going up and down during the pulls instead of a straight line like it should. He bypassed the boost solenoid to see if it would make a difference and it didn't. I suggested that the belt could be too big and slipping causing the boost levels being low and the boost levels going up and down. He checked and thought the belt was too big so they ordered a smaller one. Could the belt size cause that much of a power loss? What else could it be??

I'm not sure on the numbers. Injectors were 50 some percent. He said all the air numbers and sensors looked good

Yes I have headers. Air to fuel ratio??

On 15 degrees of timing...AFR 11.8-11.6. INJECTOR DUTY CYCLE AT 6000 rpm was 60%. MAF at 6000rpm was 220 grams per second. Boost max was 5.1 lbs. Average was around 4 lbs. By choppy I meant boost was going from 3-5lbs throughout the run. Going up and down

Send me your number in a pm I'll send you the pic that way.

needs more boost.

Around how much boost should I be running?

What else could be causing stock power coming out of this???

First question is it misfiring?

If no, then is the belt slipping?

If no, Is the BBV actuator closing during WOT?

Figure that stuff out first.

And the solenoid can fail separately from the actuator.

Originally Posted by matt5112

First question is it misfiring?

If no, then is the belt slipping?

If no, Is the BBV actuator closing during WOT?

Figure that stuff out first.

And the solenoid can fail separately from the actuator.

No misfiring. I'm thinking the belt is slipping because of the boost levels going up and down like a roller coaster throughout the each run. Not sure about the BBV. how can I tell if its closing?

Remove the hose on the top and cap it off on the vacuum tree side. then go wot.

If you see more boost, then it wasn't closing and you need a new one.

Originally Posted by matt5112

Remove the hose on the top and cap it off on the vacuum tree side. then go wot.If you see more boost, then it wasn't closing and you need a new one.

Which hose is that? There's 3 hoses coming out of it right? The guy doing the dyno bypassed it by connecting 2 of those hoses. Not sure which of the 3 though.

One of the first runs on the dyno the torque maxed out at 350 but the horse was like 170 with 10 degrees of timing and very low boost. The he hooked up the wires differently under the hood then both numbers were around 170

take a picture of what your guy did.

That sounds super sketchy.