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Ron I didn't belive it either until I read t he Car Craft artical that somebody posted here. As a matter of fact I think it was 39. I don't have the link but I'm sure it can be googled w/o much effort.

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39 on one particular motor; sure. The reality is that you could gain anywhere between nothing and 100hp: it depends on the build.

It really isn't rocket science; the amount of power gained by switching to tube headers from manifolds depends on a number of things;

- the manifolds in question. Our HP manifolds are decent - better than GM BB manifolds and worse than Hemi or MW manifolds.

- where the other bottlenecks are; there isn't as much point in increasing exhaust flow on a motor that has a crappy flowing intake, heads, etc.

The best example of a motor that needs headers that I can think of is a 427 L88 BBC which due to it's restrictive factory manifolds, good flowing heads and a radical solid lifter cam can gain somewhere around 80 - 100hp with the swap. My guess is a stock street hemi or Max Wedge falls on the other side of the spectrum; the stock manifolds flow much better than their GM counterparts. An RB with HP manifolds falls somewhere in between......depending on how it's built. I would guess that a bone stock 375hp 440 Magnum would see a slight increase along the lines of 10-20hp......is that worth it? that depends on how you weigh the pros and cons; there is no right or wrong answer.


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Dave