up stainless marine 4'', I have a pair of dry set up good for big cams 1200. art 617 833 3327, going to a bigger set 5'' for new 572 Dean Gellner blower motor.

SO TRUE, my buddy has a 2nd leak 2 yrs in a row on his etops, but there about 5yrs old:rolleyes:, if its bad hes got a line on hardin marine headers with the black top like a gil top header bottom.:evilb: ugly. you need to drain and rinse your cmi headers which he was not good at.

I had a similar project on my previous boat and I went the the IMCO, PowerFlow system. The exhaust was reasonably priced for high performance exhaust, had great performance gains and sounded incredible . Good luck with you choice.

Ray,
I actually wanted to use the KE's on my 496HO and was told that the KE's would only fit the 502 type heads. I went with the Dana Torque Flow manifolds instead.

So the KE's cast header manifolds will actually bolt on to and properly align with the exhaust ports of a 496HO heads? Is there a special gasket required to seal the KE's to a 496HO head?

I noticed in this thread some consistent pros and cons of headers vs. performance manifolds, ie headers make more HP and manifolds are more durable. I was under the impression that a good performance exhaust manifold will make better TQ numbers than a performance header. Is this true? I have Stainless Marine manifolds on a 454MAG w/ a Crockett cam upgrade and I have to say the boat sounds and runs strong for a 454.

Most standard performance marine engines that are normally aspirated will always make more torque with longer exhaust runners or tubes and they will extract better and generally make more power if the individual runners are in the 20" to 30" equal as possible lengths.
Most of the aftermarket performance exhaust manifold systems are short runners 6"-10" runner length and even though they are much better than the old log type manifolds (pre 1996 approximatly) Merc and others used to put on older big block and small block marine engines they will not make as much power or torque as the longer runner or tube length headers or header manifolds, where the runners are longer and merge into an actual collector either just before or in the risers, such as Dana, KE, Imco and the tubular header systems like CMI, Hardin, Stellings, Lightning and others. Its also important to remember that different exhaust manifolds and headers have different reliability, life and structural differences that must enter into the comparisons and selection process to pick your best product for your application.
As for the KE header manifolds, yes they will fit the 496 head, but there are no provisions for a kit where the oil filter bracketry and other ECM bracketry and such is provided , so you would have to customrework or make special brackets and remote oil filter accessories and such to use these on a stock Mercruiser 496 or Volvo, etc.
Also some aftermarket header manifolds such as the KE or Imco Power PLus header manifolds may in some cases present height problems for overall heights with respect to hatch and engine lid covers for some boats.
I keep saying to clarify! Headers and Header manifolds are HEADERS & performance exhaust manifolds are MANIFOLDS!, there is a difference! Please inform your self with the differences and make your decisions carefully based on your budget and needs & performance results wishes! And also rember that generally its "Different Strokes for Different Folks!"

Best Regards,
Ray @ Raylar

Ray, Many consider you the marine professional that knows more about the Merc 496 (8.1) motor then anyone. Tell us this, have you tested a set of KE cast headers on a Merc 496 motor? If yes, what was the result.

This again.........
 

Ray and Larry build a great engine, and their kits are superb. Their advice is worth paying for so getting it for free is a privilege.

If you can stretch for the headers then do it,
CMI, lightning and Stellings all make a great product.

If you cant I'd look at the imcos or the danas,
I and many others have had great long term luck with the imcos.

Stainless Marine has a good rep as well.

EMI?

Do a little poking around to see what various builders say - most particularly Eddie Young about the EMI's reliability.



UD