Monkey Spanker

Looking for an "EXACT" answer to this. "NOT" an opinion, please only reply if you know this for sure. At what level does Mercury start putting Inconnel exaust valves in their motors? Do all motors have them in, or just high horsepower models? Once again, only if you know for sure. Thanks.

800XCR

iTrader: (2)

The answer is it depends.....but the most recent stuff started with the carb HP 500 and up.

PatriYacht

The Cyclone 454-400hp used them and the 454-420hp. Any engine above them in hp used them.

Monkey Spanker

Man, this thing got buried quick. I figured there would be more replys being everyone seems to think Inconnel valves are the "ONLY" valves you should put in a marine head. Apparently they aren't as much a necessity as people would have you to believe?? CP performance only lists them for a BBC, why not sbc sizes, or others?

jpclear

I'm probably get in trouble here, but: Inconel( Manley owns that particular name. It's their EXTREME DUTY exhaust valve) or Ferria's " Super Alloy",or REV's equivalent to the "inconel" valve will stay connected with the high heat, long duration WOT runs and elevated spring pressures that many of our engines are subjected to. Believe it or not, the marine application is actually MORE demanding than that of the hi-reving drag, street, or short-track racer. SO,- Hi-Perf marine application?? Inconel or the equivalent for the exhaust valves !! Nothing less!! I have personally paid the price to learn this lesson and it wasn't cheap! --- Jer

PatriYacht

I agree with JP. Who builds a 454 and plans on less than 400 hp?

deboatmon

No one mentioned the INCONEL's increased ability to withstand moisture at high temps. In wet exhausts some amount of moisture inevitably may get to the glowing red hot exhaust valve. That is certainly more possible with higher performance cams. I belive that is where the INCONEL separates it's self from all others.

Monkey Spanker

Talked to Manley today about inconnel valves. Strangley enough, they only offer them for chevy motors. The severe duty valves are rated for 1380 degrees, the inconnel are rated for 1500 degrees. Are they stronger? yes, but only marginally so. If you have a high horsepower motor "that you are going to run WIDE OPEN for a long time" they would reccomend them. Are they necessary for the guy who run's WFO for less than 5 miles?? No. its the same as rods and crankshafts, do you always need billet cranks and rods?? No, but are they the best available? Yes. He said I'll have no problems at all with the severe duty's. Most valve problems are from running too lean, which raises the temp and kills them.

Monkey Spanker

Maybe John Force has a few old ones laying around I can dig out of the trash..................If Manley doesn't make them for Oldsmobile, Ford, and Chrysler's, why don't all of those motors suck valves??? Yes, a 540 with a 8-71 turning 6000 rpm making 750 hp is going to be hard on parts, especially exaust valves. I ran a 350 chevy in my last boat for three years with STOCK 1.5 car exaust valves, I ran it VERY hard, lots of WFO time, two owners later(and two blown outdrives) it's still running like a raped ape. No valve problems at all.

Hang Time 27

Common sense answer:

They don't make them for the other engines because there is NO DEMAND for them. No one is putting those engines in boats. Unlike cars, boat engines are ALWAYS under load even at a "easy" cruise - a car would have to be constantly towing something up a mountain to equal the same use/abuse that a boat creates - End result is higher exhaust temps that have a longer time to saturate the valve and seat area. If drag races were 5 miles long, and up a mountain, with chance of water in the exhaust, then maybe we'd see them for the other engines................