Best Exhaust Valve Choice for Truck Engine

I have a customer who is singing the blues about his 460. He has one in a small dump truck that'll haul about 8 tons of rock or dirt. Someone built at least a couple of engines for him that either blew up or were poorly built. He brought his heads to me after having a problem and they were a set of D2VE heads with no hardened seats but the builder had chrome moly retainers and very heavy valve springs, moly pushrods too because they were "better". I did a set of D3VE's that he had and I fitted them with hardened seats. All was well for about 6 months until it dropped the head off of an exhaust valve and did some damage but didn't total the engine. It's a valve that's on the exhaust crossover port and I think I'm going to block that on this go round but I'm curious what most people feel would be the best exhaust valve to use without breaking the bank. I think I should use some of those inconel valves that were used in the later truck engines but will a stainless steel valve do the trick? I have a set of those on hand..... We know a low compression hard running engine like this one will make some killer EGT's and I'm not totally sure that this thing has a stock cam so it might have some extra exhaust timing which would only aggravate the condition. I can see that the engine has not been over heated but the area on the deck that's under the exhaust crossover has turned blue!

Stainless is going to be a step up for sure, but they're still not going to be as good as inconel. You might want to call the manufacturer to find what material they're made from and if they're suitable. Lots of different grades of stainless out there.

If I were in your shoes, I'd pony up the $20/valve for factory replacement inconel valves. The customer has been through two failures already.

X2 on the inconel valve , might hurt up front but cheaper in the long run

Not sure on price anymore, but back when I was using 460's for well motors, I was using the Stelite valves as they were the only thing that would last in these propane/natural gas motors. They were pricey back then, but they were worth ponying up the money for.

Dave, while Inconel would be the best, I think the Manley Severe Duty might be cheaper and work pretty well.

Bret

Turning the deck blue on the block? WOW, that's some major heat.

Sounds like it's time for an IDI swap? I just don't see gas engines with ultra high loads being reliable with the EGT scenario.


Greg

I manged to find some late model stock 460 replacement Inconel material valves for about $15 each so that's what I have coming. Also I did find that the customer had the exhaust gaskets installed backwards which in blocking about 1/4 of the port probably didn't help exhaust valve temps either. Another modification I've now done to the heads was machine a recess at the intake flange side so that I can block the exhaust crossover with a piece of .125 thick steel. This should help keep some of the heat levels down too.

It will be interesting to see what those changes will do the heat the engine obviously produces.

I wonder if an EGT gauge might be useful? Probably not, it sounds like the truck lives with a heavy load and a wide open throttle.

Greg

Would late timing be hard on the valve in a heavy loaded engine?

Retarded ignition timing, overly rich or lean mixtures, excessive exhaust cam duration and low compression all contribute to high EGT's. Low compression is something we have to live with on a truck engine. Overly advanced ignition means death in a truck engine and this guy's been careful to get the timing using a light so I don't think that's a problem. He says that the engine runs really well too.

At first I thought that maybe it had hung a valve and the valve got hit by the piston and then broke. This was not the case. The guide and valve stem looked perfect. It was broken right down at the end where the valve stem gets larger and forms a radius at the back of the valve. I compressed the spring, removed the keepers and it just slid right out without any trouble.

What kind of valve/guide clearnace are you running? Those valves really grow with all that heat.

Isn't that point, on the stem, right ehere the 2 pieces were welded together?

.342 and .3445 is what I get on the stem and guide clearance. It's somewhat loose but I thought that it would be fine and not cause any trouble. Again that area looked great on the valve that failed. And yes I do think that it failed right where the valve is welded together(I assume that stock 460 valves are 2 piece designs).

In the past I've had 391 engines that have been damaged from an exhaust valve failure but in those it seems like they came apart about 1/2 inch farther up on the stem. I've also had some 391 valves come in that were starting to neck down in that area, failure was not far away in that case.

My new exhaust valves arrived today and just for kicks I weighed them: The stocker weights 102 grams and the new inconel material valve 111grams, quite a difference.

10% heavier is quite a difference. I never weighed the Stelite valves that we used to use.

I thought it was a pretty significant difference too for a valve of the same dimensions as the ones I removed.