Headers and exhast size?
Melting Slicks
Joined: Jan 2000
Posts: 2,386
Likes: 3
From: far, far away
Has everything to do with power output and air (exhaust) flow needed. My little 355 with a mild cam is rated at 330 hp @ 5000 rpm, and 1-5/8" headers into 3" collectors, reducing down to 2-1/2" pipes, will probably be about as good as I can get. Bigger primaries on the headers would probably hurt the torque, and I don't think bigger pipes would do anything but cost more money.
If that motor were set up to pull more rpm, it would need bigger header primaries and maybe bigger pipes. If it were a bigger motor (454 or 502 instead of 355) it would need 1-3/4" headers, and if that big block were set up to turn 6K or 7K rpm, then maybe 1-7/8" headers and 3" pipes would work best.
If that motor were set up to pull more rpm, it would need bigger header primaries and maybe bigger pipes. If it were a bigger motor (454 or 502 instead of 355) it would need 1-3/4" headers, and if that big block were set up to turn 6K or 7K rpm, then maybe 1-7/8" headers and 3" pipes would work best.
Thread Starter
Safety Car
Joined: Oct 2000
Posts: 4,282
Likes: 172
From: Lake Wylie, South Carolina
Bottom end is a +.030 454, polished 3/8 rods, SCAT crank and SP 10.5:1 pistons. Cam is a CCXtreme 292 solid, Intake is a performer RPM with a Demon 800 mech sec. Brodix Race Rite 110 cc CNC'ed heads with 2.25 intake valves. M20 4speed and 3:70 gears. Target rpm is 2-6500k
Instructor
Joined: Jan 2005
Posts: 218
Likes: 0
From: Sheridan IL
at least a 2" primary I would go alittle bigger and for the collector I would go with a 3 1/2". Exhaust at least 2 1/2 but you could go with 3. Check into a set of step headers you will gain alot of power but they will set you back a few $$$. 
Race Director
Joined: Dec 1999
Posts: 11,096
Likes: 990
From: Sierra Foothills CA
I'm running Hedmans w/ 2" primary tubes. I'm pretty sure it's the only size they make for our Vettes. I've seen it said that 1 7/8" primaries like Hooker makes is better for torque but I have an abundance of that w/ the 2" as it is & want all the top end I can get. You have more cubes than I do with the heads & cam to really pull RPMs so I'd go with 2" if I were you. You'd probably pick up some ponies in upper RPMs w/ 3" pipes but it's pretty expensive for what you'd gain. I may try it if I can find a quality shop to do it that won't bend me over in the process. 
