Last edited by outriggers; 01-06-2010 at 11:04 AM.
Anyone know if the new E-Tops for the 496 has had any related problems as of yet?
I don't know if there is anything to this thought or not , but could it be that since Ed sold CMI to the new corporate owner, the weld problems and leak problems on CMI's have possibly increased disproportionatly. I wonder if the processes after welding such as heat treating or such or the material of the weld or tube material has changed somehow to exagerrate the problems that seem to be appearing in some Sporttubes sets both 496 and HP525?? Or was this a CMI condition from day one?? Just throwing a thought out there as I wonder if this is really a big problem or just a normal thing with a lot of over exposure here on OSO? I know among a lot of 496 owners and engines with CMI's we have seen a moderate percentage of leaking CMI header sets, both new and lightly used applications.
At this point we have stopped recommending CMI header upgrades to our customers until we feel comfortable with the overall possibility of a no-leak CMI header.
Has anyone seen this same condtion in the Stellings or Hardin stainless tubular headers or is this pretty much more isolated to CMI??
Ray @ Raylar
I think the problem is isolated to salt water boats. Has anyone had a failure in a freshwater only boat?
Water type does not seem to be the issue in the leaks and problems we have been exposed to and seen first hand.
The only headers we are now recommending are the Dana and Kieth Eikert cast type header manifolds that have been hard anodized for salt water use if so used and carefully mated to captains call-silent choice if so equipped.
We do not have enough personal expierence with other header manufacturers such as Stellings, Hardin, and Lightning to make a factual statement about how they are performing from a leak or cracking standpoint.
We are also careful to inform customers that routing exhaust outlets down and around thru right angle S-pipes and such may be a problem on bigger horsepower engines were larger cam durations and greater exhaust flow with water in the system ahead of the S-pipe or large direction changes can sometimes back water up into the header and ultimatly into the engine.
We do all our break in and dyno testing with the engines fully accessorized with raw water pumps, wet exhaust just as they will be in a boat and we have actually have expierenced water intrusion back into the engines exhaust side on the dyno with S-tubes installed right behind the riser outlets and some problems with switchable exhaust diverters like captains call- silent choice type even at idle rpms due to what we call exhaust water bounce back syndrome. This has happened with engines with fairly mild cam durations that do not revert with the exhaust properly routed and exhaust water plumbed at a better entry point.
Bottom line, on my boat I would not run a high performance engine 500HP plus normally aspirated with headers routed thru captains call-silent choice type switchable system or thru S-tube diverters to clear and integrated transom without dumping the exhaust water behind the switchable valves and after the drop in an S-tube system where the water outlet is faced toward the actual transom outlet.
This is remember Raylars opinion and is not the last word in what exhaust is right for everybody else and we are certainly not the last word in performance marine exhaust headers!
Ray @ Raylar
Anyone know when Merc bought CMI? Like what year?
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