The first pull I did (blue line) was after all of the engine modifications except the side pipes. The red line is a pull I made after changing side pipes and nothing else.
I dont know what each modification made in HP except for the air filter and side pipes.
But my guess is this:
Original HP from roush 427 srtw(crankshaft) was 510 hp and 528 tq
950 cfm Carb add 20 hp +-
Vic JR intake add 10 hp +-
Side pipes add 15-20 hp +-
Bigger airfiter add 10 hp +-
Present rwhp 460 +- TQ 440 +-
Pic only shows Gains of side pipes.
