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Old 10-30-2006, 08:13 PM
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Mid-Length Headers

Anyone ever run or try any dyno tests on "mid-length" headers (particularly SBC engines)? I guess I've never really seen any before and have seen some on ebay lately and wondered if they were any good or not? Thanks.

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Old 10-31-2006, 09:33 PM
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"Mid length" doesn't mean anything to me. For a SBC street/strip machine header primary pipes should be about 33" long, equal length, within an inch or two and 1.5" to 1.625" dia. Any thing not this dimension will be a lesser performer. For a high winding strip only engine, primaries should be in the 24" range and 1 3/4" to 2" dia. All depends on the rpm range the engine is designed for. These wouldn't perform any magic on the street except impress the girls.
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Old 10-31-2006, 11:08 PM
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You use what you can, but I got one piece of advice from Smokey Yunick that I like to live by. The "proper" headers might be 30" long, but even shorties are better than the stock manifolds. I say run headers as long as possible up to optimum, but if you can't fit full-length, then run mids.

Willys36 is spot-on with those recommendations, but unless you're tuning for absolute max power, any header is better than no header.

I choose to run full-length headers for the sake of torque production on my low-rpm 454, but in actuality, I'd probably only give up a few lb-ft if I switched to mid length.
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Old 11-01-2006, 02:31 AM
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According to David Wizard's book "How to tune Chevy small block's on a budget" equal primary pipe length on headers aren't that important. Much more important is the length of the collectors.
He hasn't a very theoretical explanation on why. It is just what he actually have discovered after dyno testing a large number of engines during the years.
David Wizard is also the guy who says "I don't have an opinion, I just have a dyno..."
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Old 11-01-2006, 04:59 AM
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Heres an interesting link
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Old 11-01-2006, 08:50 AM
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I don't usaully like calulators but I'm told this one works.

www.headerdesign.com
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