408 1 3/4 0r 1 7/8
08-03-2007, 10:44 PM
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408 1 3/4 0r 1 7/8 Iam in the process of building a 408 with l76 heads and manifold with a 250s plus cam, Ive noticed all the talk about 1 7/8 headers are the go. I already own a set of long tube 1 3/4 with a merge collectors on them.. should i sell them and go 1 7/8, will they really make 20 to 30 hp difference...
08-05-2007, 10:27 AM
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I doubt you will see any gains at the track with the 1 7/8 headers. Unless its a track only car and you never see below 4000 rpm then go 1 7/8. If you drive it on the street stick with the 1 3/4. You dont want to loose the low end grunt.
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08-05-2007, 12:03 PM
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Originally Posted by Order 66
I doubt you will see any gains at the track with the 1 7/8 headers. Unless its a track only car and you never see below 4000 rpm then go 1 7/8. If you drive it on the street stick with the 1 3/4. You dont want to loose the low end grunt.
do you know anything about LS1's?
They dont need backpressure! this is not a Mod Motor ford or a damn 302/305 motor.
I ran my car with open cutouts in place of the cats. car picked up mad power when they where open vs closed. It is a fact that with a 408 or equivalent size engine you dont need the backpressure created by 1 3/4 size headers. On the L92's if you open up the exhaust... which you need since they flow like *** on the exhaust. Put some putty on the flanges of the 1 7/8 headers.... then match the heads to the primaries.
08-05-2007, 12:11 PM
#10
Originally Posted by Order 66
I doubt you will see any gains at the track with the 1 7/8 headers. Unless its a track only car and you never see below 4000 rpm then go 1 7/8. If you drive it on the street stick with the 1 3/4. You dont want to loose the low end grunt.
The old header primary tube myth again. Theres been research, and some write ups on how a 1 7/8 primary will not reduce low end torque. And in one test, they even picked up some on the lower end, over 1 3/4s.Seen similar results in house too.
Not to mention the fact that with a 4 inch crank, and 408 inches, you're not gonna miss a couple ft lbs.
