Offshoreonly.com - Exhaust for NA 650 hp bbc 540

Offshoreonly.com (https://www.offshoreonly.com/forums/)

- General Q & A (https://www.offshoreonly.com/forums/general-q-20/)

- - Exhaust for NA 650 hp bbc 540 (https://www.offshoreonly.com/forums/general-q/365227-exhaust-na-650-hp-bbc-540-a.html)

Quote:

Originally Posted by CheckmateScarab (Post 4932772)

Does anyone have actual sheets to prove GIL and the like don't handle more than 500? I'm pushing 600+ through an NA bbc with gil offshore manifolds

Wondering if there is any merit to the claims or if it's all marketing to sell headers

Its not that an engine using them can’t make 500-600hp it’s that it will probably be losing 6-8% power vs a true header.

If you study volumetric efficiency of NA engines you’ll see that some go over 100%. Up to 105-107 is common. This is possible due to a tuned length header and cam with overlap doing of bit “supercharging” via exhaust scavenging.

It’s interesting that Smittys quoted numbers seem to show that log manifolds are giving up that exact % beyond 100. Makes sense in my mind.

Full length headers need to be in the 30-40” runner range. Longer for lower, shorter for higher. The thunder n lightning is around 33” iirc. Probably giving it a nice high rpm gain.

Quote:

Originally Posted by KAAMA (Post 4932723)

I just ran across this thread from about 5 years ago.... and as best as I know the Diamond (KE design) full length cast aluminum exhaust manifold/header system is no longer being made. I don't think it's much of a big announcement anymore though.
It's actually too bad as it's a very good exhaust cast aluminum system that possess true "header" performance quality.
It would be nice if someone with a few bucks in their pocket could buy the manufacturing rights (whatever) from Diamond and get the show back on the road again.

Id be interested in doing this if anyone knows who to contact.

I'd certainly jump at the opportunity for a new pair of thunder & lightning exhausts. Nothing beats them! I've been keeping an eye on this thread for the last few years : Thunder-N-Lightning Cast Aluminum Exhaust Headers - Offshoreonly.com
Contact is Diamond Performance Parts. Bill @ 302-521-0123 I think.

https://mattyorke.wordpress.com/wp-c..._ios.jpg?w=640