Well i finaly ordered my new valve springs to replace my 987's with 918's.I think i was floating valves starting at 4k so Im hopeing this fixes my no topend problem. Next its on to the exhaust wich was to be only temporary to begin with. its 15/8th headers to a stock v6 size pipe staight to a flowmaster. Im replacing it with a 3'' pipe from the y all the way back to a high flow cat and a magnaflow exhaust. How much power could this old crappy setup be robbing me?I know it was costing me but could this be a big part of my no topend problem?

 

It's hurting you A LOT having a stock V6 exhaust on an LT1. If you leave the heaers and get a 2.5 or 3 in Y-Pipe, Cat and then Cat back system you will gain a ton of power. I think the main reason for your top end problem was the exhaust not letting your engine breath in the upper RPM's. What is your HP numbers now? Most stock headed 306 LT1 motors w/ bolton's tend to be around 330 to 350 at the wheels.

 

i doubt it has 250 seriosly it dies up top. puts you in the seat good till 4k. no valvetrain noise or anything pointing me anywere other than valve springs or exhaust.. my 918s are on the way now its just a matter of the 3'' pipe.

 

I had a car with restrictive (for the car) borla/ 3 inch y pipe only do 430rwhp. We unbolted the exhaust and used 18inch collector extensions and the car did 520rwhp.

Note: That car had 260@ .050 duration so results are not typical.