question about header primary tube diameter
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Elder User
Joined: Nov 2004
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From: So. California
question about header primary tube diameter
I have been playing around with the header primary tube diameter formula and wondered how small in diameter I could go before I reached the diminishing returns in low end torque gains.
With a 359W, .040" over 351W:
.040" thick wall tubing
-1.5" O.D. primary tube, the peak torque is 3,105 rpm.
-1.625" O.D. peak torque at 3,707 rpm.
-1.25" O.D. tube the peak torque is 2,112 rpm.
-1.375" O.D. tube the peak torque is 2,594 rpm.
Can I really go down to 1-1/4" or 1-3/8" O.D. and expect to gain any low end torque over a 1-1/2" primary tube header?
This is where my engine is. I swapped my camshaft and lifters for a hydraulic roller setup. I got the Schneider 266-78RH. The cylinder heads and intake manifold have been ported.
With a 359W, .040" over 351W:
.040" thick wall tubing
-1.5" O.D. primary tube, the peak torque is 3,105 rpm.
-1.625" O.D. peak torque at 3,707 rpm.
-1.25" O.D. tube the peak torque is 2,112 rpm.
-1.375" O.D. tube the peak torque is 2,594 rpm.
Can I really go down to 1-1/4" or 1-3/8" O.D. and expect to gain any low end torque over a 1-1/2" primary tube header?
This is where my engine is. I swapped my camshaft and lifters for a hydraulic roller setup. I got the Schneider 266-78RH. The cylinder heads and intake manifold have been ported.
FTE Legend
Joined: Jun 2006
Posts: 31,930
Likes: 1,499
From: Ottawa, Ontario
Ahh OK. What are your predictions for HP and TQ peaks from the motor? The exhaust system can massage those numbers up or down in RPM a little but it won't totally change them so the exhaust system should be sized to work with it as much as possible.
Lead Driver
Joined: Aug 2003
Posts: 6,305
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From: Boulder Creek, Ca
Came across this article few years ago and can not recall if the info would apply, or be of any help?????
Header Basics - How Headers Contribute to Horsepower - Car Craft Magazine
Header Basics - How Headers Contribute to Horsepower - Car Craft Magazine
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Elder User
Joined: Nov 2004
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From: So. California
I don't have any predictions yet.I want as much torque right off idle around 500 to 1,000 rpm as I can get and secondly I want to stretch that torque curve out as far as I can get while retaining a flat torque curve.
I have the Schneider 266-78RH.
I really want to build the middle/peak torque to its max and balance the low-end and top-end torque.
I have the Schneider 266-78RH.
I really want to build the middle/peak torque to its max and balance the low-end and top-end torque.
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