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Old 11-06-2019, 06:03 PM   #106
Turbo, what?
klr142's Avatar
Join Date: May 2004
Location: OR

Yes, I am bumping this old thread.
Originally Posted by Stereophile33 View Post
I just want to post this up so hopefully it will become internet lore.

We've been doing alot of head stuff and for turbo and NA folks using camshafts under 12.5mm of lift and for that matter stock unported intake manifolds, the 531/405 head is a waste of your time as it won't make more power, especially under the curve.

A well ported/filled 530 will make more power than a 531 anyday with a cam under 12.5mm. If going to a bigger cam, you bet, make the jump for the 531/405 heads, but you should also consider one of Nathan Kahler intake manifolds at that point.

So, how about that more info/graphs, Jonathan? I know that info is well out of your hands now and lost forever, which is a damn shame.

Also, what is likely most relevant to a lot of people on here, is how these differences show up in the real world with unmodified 530 and 531 heads, instead of just looking at a well ported/filled 530 head, which is much more rare than even a 531 head.
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