Hey guys,
I know I'm obviously going to have a gain when I go to headers, but I was wondering about how much? I have a 330hp 406 running through LG4 manifolds and stock exhaust right now. I'm going with a heddman shorties and y pipe and a 3" hooker cat-back. Any suggestions??

Thanks

 

You've got a certified 330 horses through the LG4 manifolds? Impressive!

Don't do the Hedmans. Little big mistake. As in, the primaries are too little, you'll be making a big mistake.

Belly up and get 1-3/4" primary SLP's. They are your only reasonable choice with that size of engine. With the Hedmans you can only expect to get about half of the gain you'd get with the SLP's, which I would predict would get you over 400. The 3" cat and cat-back should be okay for a relatively mild 406. Dual 2-1/2" cats and 3-1/2" cat-back would be better, though.

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82 Berlinetta, orig V-6 car, now w/86 LG4/TH700R4, 2300 stall TC. Ported World 305 heads, Crane PowerMax 2050 cam. ZZ3/4 intake, oil pump, pan & baffle. Accel HEI SuperCoil & module. Hooker 2055 headers, 3" Catco cat & 3" catback w/dual-opposite Flowmaster 80. 2.93 limited slip. Spohn SFCs waiting to be installed. AMSOIL syn lubes bumper-to-bumper. Daily year-round driver. Best ET, speed TBD...
57 Bel Air, my 1st car. '66 396, 9.7:1 forged TRWs, Weiand Action+, Holley 750VS w/4150 conversion, GK 270 cam, Magnum rockers, Jacobs Omnipack, 1-3/4" Hedders & 3" Warlocks, TH400 w/TCI Sat Night Special conv & Trans-Scat shift kit, MegaShifter, 3.08 8.2" 10-bolt w/Powertrax, AMSOIL syn lubes bumper-to-bumper. Idles smooth @ 700 RPM in D. Best 15.02/95.06 @ 5800' Bandimere (corrected 13.93/102.4 @ sea level).