Ok I installed a ported plenum and SLP runners, I ported and matched all the gaskets to the intake to runners and runners to plenum. I did a tuneup with all this changining out of stock upper intake with new coil, cap, rotor, plugs, and wires. Also tps, IaC, and maf sensor. With the stock upper intake before the change over the lowerend torque was unreal and the car would rip. Now at the line it is a nice launch when punched but not as aggressive. The car though has unbelievable top end itself and not asthmatic as it was. Is this because the slp runners are shoeter in length to the stock or because of the siamesing on the runner ports itself? Another question I am going to change out to a hiflow cat system soon because of this deteriorating exhaust also would this have a major effect because of more airflow?

 

Both. They are slightly shorter than stock and the siamese also cuts down on the length. You have traded some low end torque for higher end horsepower.

Regarding the exhaust system anything you do to upgrade it will help. The biggest seat of the pants improvement I made was the change to my SLP headers.

Back to the lowend power loss. I have been trying to kill off some low end torque and trade it for higher end horsepower. My SLP runners have been modified to such an extent that there is virtually no runner left. Only siamesed. All I have is the length of the Edelbrock manifold and what is in the head. However it still shreads the street tires and lights them up real well. Allen

 

This sounds like what should happen. You basically moved the powerband a little. A cam and properly stalled converter would be a good idea... after you get a full exhaust system ( Headers instead of manifolds, and full 3 inch mandrel bent catback, with a high flow cat)

 

Did you check your ignition timing? If the timing is retarded for some reason, you will see a power drop off at low rpm. Try running 8-10 degrees base.

www.geocities.com/dzperf

 

Yeah did you mess with the timing or distriutor?