articfriends

I am contemplating changing exhaust on my single engine blown 540,I currently have lightning headers w/silent choice and i'm either going to modify them(eliminate the silent choice and add water further back) or replace them because of reversion concerns. Every place i have talked to has something different to say. I am looking at EMI thunders,EMI claims they outperform cmi elbow tops and that cmi elbow tops outperform lightning headers. Some people say aside from stellings(too pricey for me) that CMI's are the best built and performing.I also looked at the cyclones by hardin but i haven't been impresed by hardin marine products (my 14 qt oil pan fits like crap). Anither option would be the stainless marine high torques. I am already 3000$ over budget on motor so keeping the price of the new exhaust at 2000$ is pretty appealing. I don't run in salt water so the added benefits from the cmi's high quality stainless aren't important. My lightnings still look brand new so i can recoup something from selling them. I'm just looking for the most bang for the buck,anyones experience or opinions would be appreciated,thanks,Smitty

Vinny P

I am going through a very similar problem. While out testing my new 540 a couple of weeks ago, I ran into what I thought to be cracked Gil WetOffshore manifolds. I had water in the manifolds upto the exhaust ports on the heads. Some water must have gotten into the engine, but not enough to show up in the oil or wash out the plugs. I pressure checked the manifolds and risers. I found no leaks even after heating the inside of the manifolds with a turbo torch. The only possible explanation is reversion. I found that hard to believe being that my risers dump the water just in front of my tips. I don't have what I consider to be a radical cam. At 0 lift I have 61* of overlap. It is a 114* lobe seperation, 238 * and 248* duration @ .050"

After making several calls, it seems that the exhaust of choice was CMI elbow tops. While talking to Fred @ Trick Marine and Teague, they seem to have had good luck with the CMI's. In fact, Teague only sells CMI's. They told me that they have seen many reversion problems with aluminum manifolds. I wish I knew the final outcome of this to tell you, but due to CMI sticking it up my @$$ for the last 2 weeks, I don't have the tail pipes. The headers are mounted on the motor waiting for the tails. I was told today that the tails went out next day air and I should have them tomorrow.

articfriends

When you were researching did you consider the stainless marine hi torques or emi thunders,they seem to have high risers and supposedly outperform the CMI's? I test ran motor on a stand and i was getting water in the header at cyl head exhaust port. I was surprised because the cam is barely bigger than my old one-old 228/236-new 233/240,Smitty

Vinny P

No I didn't look into those. I had CMI's in mind. When I called Teague for information, they had a one track mind towards CMI's as well. I figured Mercury had them on countless HP500 EFI motors without any issues that I rememeber hearing about, so they should be good enough for me.
I am not thinking that they will produce a significant horsepower gain over a good set of aftermarket aluminum manifolds. I am hoping that they solve my reversion problem.

Brad Zastrow

One other thing to consider. Headers look so much better than manifolds!!!!!

Sean H

cmi's....

PatriYacht

Smitty, I think the new heads have something to do with the reversion. I had no reversion before switching to the AFR heads. After switching the reversion was so bad it would stall the engine at a 800 rpm idle. This was with the same cam. I think the heads flow so much, they act like the cam is larger. I had to change my tailpipes to dry and dump the water thru the transom.

articfriends

Ian,I tend to agree with you. I had motor runing in driveway with headers bolted on and you could watch the water going backwards up the header!How big of cams are you running?

PatriYacht

I was running 244/256. Too big. This year I'm running 236/240. Donna told me you called but it was too late to call back. Should I call tonight?

Stormrider

I've got the Stainless Marine HiTorques.
come w/ a 5yr warranty, and didn't want any cracking headers.
Not as loud as headers either.
And don't have to sit and polish the header either... only the riser.
But the hi torque 2s are only good to 600hp... i think.