SPECS: BALANCED 355CI 98VORTEC BLK, SPEEDPRO FORGED FLAT TOPS, STK 91 350 HEAD CASTINGS MILLED .030, POLISHED/ PORTED TO 1.55X1.55 EX GSKT & 1.34X2.21 INT GSKT MANLEY STAINLESS SWIRLPOLLISHED UNDERCUT 2.02INT & 1.6EX VALVES .600 LIFT COMP SPRINGS, COMP CAMS HYD ROLLER 220/230 DUR 114 LOB SEP .540/.540 LIFT W/1.6 ROLLER ROCKERS, TORQUESTEP HEADERS 1 1/2TO1 5/8 PRIMARIES TO 3"COL TO 2.5” Y-PIPE TO 3” MAGNAFLOW CAT BACK, 90 VETTE INT PORTMATCHED TO HEADS & PORT MATCHED TO LARGETUBE RUNNER GSKTS, SLP SIAMESED 2" DOWN, RUNNERS PORTMATCHED TO LARGETUBE RUNNER GSKTS & PLENUM PORTMATCHED TO LARGETUBE RUNNERS, 58MM BBK THROTTLE BODY W/PLENIMUM HOGGED OUT TO FIT ACCEL 24# INJECTORS, BBK ADJ. REG, MSD COIL CAP WIRES ROTOR & 6A BOX ACCEL MODULE, SUPERCHIP, NO A/C & NO EMISSIONS STUFF. BEEFED 700R4 W/2100 STALL, 3.23 GEARS. NOW FOR THE STINKY RESULTS. AFTER A FEW HOURS ON THE DYNO MY BEST # WERE 251.3HP/313.4TQ W/THE FUEL PRES @ 39LBS & 11DEG OF INITIAL TIMING. FIGURED MY NUMBERS WOULD BE AROUND 280HP/360TQ CAUSE B4 I HAD A STK 350 W/ZZ4 CAM, ALL THE MSD STUFF & THE SAME RUNNERS & PLENIUM & THROTTLE BODY BUT WITH A STK LOWER INTAKE & WE MADE 228.1HP/339.2TQ. WHAT THE HECK HAPPENED? HEADS TO BIG? HEADERS TOO SMALL? INJ TO BIG/SMALL? CAR PULLS TO 6100RPMS BUT POWER DIES AT 5500ISH. PLEASE HELP!!!!

 

What did the air/fuel ratio look like throughout the pull? Are you getting any knock counts/knock retard? Were you just tuning using fuel pressure and initial timing?

 

If you're still making reasonable power at 5,500 RPM with the long TPI intake runners, consider yourself fortunate. They really aren't made for higher RPM flow, after all. The larger runners may help a bit, but you've probably used all that up by the time you hit 5,500 RPM. You may have to revisit the intake flow to raise teh torque along a lower RPM range, making your peak HP at a lower RPM. The formula is still the same, so if you make and use the torque at the lower RPMs, your peak power will be as good or higher - just not at or above 5,250 RPM.

 

we started all dyno pulls around 2800-3000rpm's. air/fuel was a little rich. 13.7 at start and going south through the pull to 12.9. we didnt wanna lower the fuel pressure any more b/c 39lbs is kinda low. there were no knock counts/retards. does this mean anything?--i have a k&n cone filter on and when we took it off it made less power and also when we put an lt1 style oval to round boot we made less power with that too. we took the exhaust off and only made 5.2hp/7.4tq more....