Griff

I've read this whole thread and it all boils down to spending an extra $150 for a set of inconnel valves.

It's like buying insurance. Weigh the risks and go from there. Merc did and they chose inconnel.

Steve Snider

The Inconel exhaust valves are more necessary in a marine engine due to the motor being under a constant load and high exhaust valve temps. The formulation for todays gasoline makes for hotter exhaust valves. The majority of marine big block Chevys fail due to valve train components. I believe in doing the heads/lifters every 200 hours in naturally aspirated motors and no more than 100 hours in blown motors. In my opinion the weak link on a big block marine Chev is always the valve train.

mcollinstn

Inconel Thermal Conductivity: 6.6 (BTUinft2h*F)
300 series Stainless: 9.4 (BTUinft2h*F)

Two benefits: Maintains a more even valve face temperature, essentially "buffering" the heat cycling that occurs when a hot valve smacks against the valve seat. A less cyclic temperature curve minimizes thermal fatigue.

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Inconel Thermal Expansion: 7.2 (microinch/inch*F)
300 Series Thermal Expansion: 9.6 (microinch/inch*F)

Less dimensional fluctuation in an extreme heat cycling environment. More consistent valve sealing contact area, more consistent valve running length.

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Inconel valve face operating range: up to 1500*F
Stainless face operating range: up to 1275*F

No explanation needed.

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Density/Mass: virtually identical.

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Inconel (or equiv) valve availability: Ferrea catlogs them in
Chevy BBC 3/8
Chevy BBC 11/32
Chevy SBC 7mm
Chevy SBC 5/16
Chevy SBC 23* & 18* Nascar heads
Chevy SBC LS1
Mopar Hemi 11/32
Mopar Hemi Dart, BAE, AJR heads
Ford SB Windsor
Ford 4.6 SOHC
Acura DOHC
Ford Escort/Focus DOHC
Honda DOHC
Honda SOHC
Mazda SOHC
Mazda DOHC
MiniCooper DOHC
Mitsubishi V6 DOHC
Mitsubishi I4 DOHC
Nissan I6 SOHC
Nissan DOHC all
Saturn DOHC
Subaru DOHC
Toyota DOHC all
VW DOHC all
MOTORCYCLES: All Jap, Most EURO, ALL Harley

Additionally, the unmentioned Domestic V8's that can be used in a marine app, can usually use a standard Chevy or Ford valve if the seat size is changed to accomodate it. For applications that require something oddball in stem length, Ferrea accomodates them at a MINIMAL upcharge and has a catalogging process that basically makes them a catalog special order piece for easy replacement.

There is really no application that cannot be easily accomodated here. And Ferrea is just one of many that will accomodate it. Del West will make a valve for ANYTHING you can think up.

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Now that THAT is out of the way,

I heard mention of ONLY running WOT for 5 miles in a boat. Did I hear that correctly? ONLY 5 miles? How long do you think it takes to reach stable valve face temps at WOT? You think it takes more than 3 minutes? How bout 25 seconds. The remainder of your 3 minutes will be at the stable saturation temp, barring detonation creeping in. If detonation creeps in (which is expected if your cooling system and/or oiling system is borderline on its heat management) then all bets are out the window. Heat curves spike and all bets are off.

You mentioned maybe adding a "small" slower. Be advised that .001% of every boater who runs a blower is able to go forever without playing in the detonation zone. Hot summer temps, loaded boats, extended top end races with your buddy - these all end up tickling the detonation button even when you don't HEAR it. When this occurs, valve face temps will go nuts.

NO SUPERCHARGED MOTOR HAS ANY BUSINESS being torn down and reassembled with anything but inconel exhausts. Plenty of guys roll the dice and bolt on a blower with standard valves, and in the interest of time and pocket change, I'm not beyond doing it as well. But I'm DANG sure not gonna have the heads laying on my bench and bolt em back on with standard valves in them. That's like getting sloppy seconds at a Frat Party without giving her a wipe with a sock first. Just makes no sense, takes very little time, and you'll simply enjoy the ride better.

So are we debating on whether it is okay to run Stainless (Severe Duty) valves on a healthy NA (unblown) motor?

Is it okay? Sure, it's okay. A pumpgas BBC 5200rpm 600 horse motor will run very well with Stainless Valves.

Water vapor reversion at idle after a hard run is asking a lot of a hot valve. Inconel is less apt to suffer microfractures i tha environment.

Let's look at welding... You gotta join metals by recasting with focused heat in an oxygen free zone. Okey Dokey. I'm with you. On cooldown you can use water to alter the direction of the cooldown shrink cycle. I'm still with you. This fact, alone, clearly shows that you get dimensional variation on cooldown when you introduce a cooling agent (water) to a point contact on a metal in the stainless/inconel classification. Dimensional variation on cooldown EQUALS mechanically introduced internal stress risers. If it cooled in a metallurgically homogeneous fashion (slowly in a vacuum chamber) then there would be an EVEN dimensional retraction. But putting a little water on one side causes it to retract unequally. This is why you can intentionally alter the "pull" direction on your welds as they cool. But in a boat, you get a little water here and there on your hot valves. THIS CAUSES INTERNAL STRESS RISERS TO DEVELOP. They are the source of future failures.

If you don't believe it, I am SURE somebody here can send you a bunch of pictures of stainless valves with the heads popped off of em.

Point is (see thermal expansion and conductivity index comparisons of Inconel/Stainless above) the Inconel doesn't react as aggressively to the water hitting it due to holding point heat better, and then it doesn't distort as dramatically when it does suffer a small zone heat discrepancy due to the lesser thermal expansion.

Since you are still looking for advice on a Normally Aspirated application, and seem to be firmly convinced that the couple hundred greenbacks that Super Alloys will cost, here is your outline for your list to consider:

* Does my motor have wide enough exhaust valve seat sealing surface to pull enough heat out of the valve to keep it stable?

* Am I sure I will keep my fuel and spark set safely below the detonation threshold for my motor, regardless of boat load, fuel octane, age, or purity, intake air temp, and intake air density?

* Am I sure that my oiling system and cooling system have adequate reserve capacity to keep my motor at a stable WOT running temp at my predicted longest WOT run? And am I sure i have adequate alarms/flashing lights/presence of mind to recognize when there is a temperature problem BEFORE I risk detonation?

* Am I running an exhaust system that introduces water into the tailpipes FAR ENOUGH downstream that I am confident that I will not get water vapor at the exhaust valve EVEN WHEN BACKING UP in rough water?

* Am I running a cam that encourages reversion enough that, in the event that I lose a plug wire, that the resultant "dead cylinder" at idle will not require a larger throttle opening around the docks that causes one or two adjaently-firing cylinders to experience higher than normal water reversion?

* Am I THAT cheap?

Depending on your answers to the above question, I hope that you will be better able to make some sort of decision regarding your choice of exhaust valves that allows you to
1) sleep well at night
2) feel validated in your choice
and
3) keep from griping when you crunch the broken off valve face into your head, crushing the main bearings, breaking the rod, punching it out of the side of the block, and filling your shiny bilge with oil.

I'm hungry now. I think I'll go make a sandwich.

mc

Kidnova

Day-um..... after that great post, you deserve some jelly to go with that peanut butter sandwich

PatriYacht

Forget engine building, I wish I could type like that!

Hang Time 27

Mcollinstn: Great post! - of course after unloading that much, one can usuallly cancel that weeks therapist appointment........works for me at least

blue thunder

Majorly good post McC. I have several engines destroyed due to what you say about reversion and valve failure. Never another problem since I went to ferrias. Particularly enjoy the bit on using a sock to clean up before sloppy seconds. That is absolutely golden!!

BT

Reed Jensen

How could Manley own the name "inconel".?.. That is the same as saying General motors owns the name "steel", because it builds cars out of steel. Inconel, and the name inconel have been around for 50 years, long before the material was fashioned into exhaust valves. I first heard the name "inconel" for a high nickel steel alloy back in the early 60's. The airforce's X15 project planes were made out of inconel because it was the only metal that would withstand the high heat of the plane. It also made the plane so heavy that it dropped like a rock until the rockets were fired.

PatriYacht

I always thought it was called Inconel because the Inco nickel company invented it.

mcollinstn

Yeah. INCO (International Nickel COmpany).

They developed Monel, Incoloy, Nilo and several other fairly revolutionary exotic allows as well. Their best group of R&D guys was in West Virginia.


Extreme Duty is Manleys trademark for their inconel valves.
SuperAlloy is Ferrea's