I installed the same 355 motor from my '89 IROC in the vette. The previous dyno testing in the IROC showed a drop off in power above 5000rpm. I attributed the drop in the power curve to cam which was installed 6.5deg advanced as well as the 1 5/8" shorty headers and single 2.75" cat.
The previous config in the IROC made the following power:
Results as installed in IROC
Peak HP = 310 (corrected rwhp) - est 360 crank hp
Peak Torque = 376 (corrected rwlb-ft) - est 430 lb-ft crank
RPM: 3900 @ peak torque and 4800 @ peak hp
With a mind to open up the breathing and better match the rest of the airflow potential of this engine combo, the following changes were made:
- Cam installed at 1.5deg retarded
- 1 3/4" full length headers w/ full 3" dual exhaust system
- additional porting of the SuperRam intake by Morgan Motorsports
The changes did the trick and the power band extended a solid 1000rpm!!
Results as installed in the vette:
Peak HP = 348 (corrected rwhp) - est 400 crank hp
Peak Torque = 381 (corrected rwlb-ft) - est 440lb-ft crank
RPM: 4200 @ peak torque and 5500 @ peak hp
