Valve seat recession on iron heads and stainless valves

[PackardV8]

We routinely install hard exhaust seats on all the old iron heads and in a few flathead blocks. Recently, an "expert" told a customer not to have the hard seats installed, but if he used stainless valves, there wouldn't be any problem with exhaust valve seat recession. What do we know about this first hand?

[modok]

I rather doubt anybody makes exhaust valves that are not stainless in the last 50 years.
99.9% of exhaust valves on earth are stainless. Are the exhaust valves original? Get a magnet and find out.

I have noticed stainless intake valves do sometimes wear the seat slightly less than steel ones, but I have no idea about carbon steel exhaust valves, other than if I had any I'd be afraid to run them.

[PackardV8]

HI, Glen,

Thanks for the reply. If you were building an engine for your restored classic, assuming the new repop valves would be stainless, would you install hard exhaust seats?

[turbo2256b]

I did a comp valve job on my DOOE heads using SS valves put over 160K on them like 0 seat wear. Ported them reseated valves got at least another 50K on them. Older heads used during the leaded days seats were seasond by the lead seem to do ok unless the seats are cut to deep or much larger valves are installed

[statsystems]

I rather doubt anybody makes exhaust valves that are not stainless in the last 50 years.
99.9% of exhaust valves on earth are stainless. Are the exhaust valves original? Get a magnet and find out.

I have noticed stainless intake valves do sometimes wear the seat slightly less than steel ones, but I have no idea about carbon steel exhaust valves, other than if I had any I'd be afraid to run them.

I've never seen a valve that wasn't some form of stainless steel and certainly none that were cast iron.

I can't count how much money I made off of heads that came in with SS valves and someone told them they didn't need hardened seats. They were pissed when they were charged to repai the heads and install hard seats.

[modok]

Many of the people I have worked with over the years told the same story.
Short version: Customer thinks hare seats not needed, they are back next year to have seats installed.

I know some do get away with it, but I don't know what they are doing right. It might have something to do with tune.

[createaaron]

You should take into consideration the fuel that will be used and the application. Is it going to be a high load bearing engine, low mile classic, daily, race, etc..

I have also been informed of the same claim of using stainless steel valves and not installing hard seats. I initially came about this doing a set a 429 cobra jet heads as they don't have enough thickness under the oem integral seat so a smaller thickness seat must be used OR stainless valves. The customer went the route to use stainless valves and keep the integral seat. Ill report back to this post once the customer has miles on the heads. This will be a mostly mostly strip some street on 91 pump gas.

[MadBill]

Yes, duty cycle is a big factor. A taxi that never leaves the big city might go a couple of hundred thousand miles on seats that would succumb to ten thousand worth of city-to-city flat-footing it in a cube van.

[Truckedup]

1948 Chevy factory engine specifications say the exhaust valves are high chrome steel....or what we call stainless steel ?...They may have been original equipment before this ....

[mag2555]

There's no dought that factory valves run on no lead will get chewed up faster than a cast iron seat will, and that both will erode faster as the main seat width is dropped back from about .075" and or the spring pressure is jacked up above 125 psi and or power levels / heat is jacked up from what I have seen!

I have also seen that with out question that running even factory Exh valves in a motor of a car that after a rebuild was run on a tank full of leaded fuel will not see any ware or resession issues if from that point on every other tank full is half leaded fuel!
If your gonna beat the pants off it then you need lead or be ready to pull it down in 15k miles!

[novadude]

Seems to be a lot of varied opinions on this. Many claim hardened seats aren't needed unless the engine will see a lot of sustained high load conditions. I was of the understanding that it's not a big deal for a typical muscle car street cruiser that might see 3k miles per year.

Something I am wondering:

Amoco was pushing unleaded gas ("white gas") way back before anyone was thinking about hardened seats. Did Amoco gas wreck motors back in the old days?

[Truckedup]

About 5 years ago I rebuilt a 292 Chevy 6 that came out of a dump truck...This engine probably spent a lot of time under heavy load....Supposedly about 100k original miles..The engine was a 1964, worn standard bore...The exhaust valves were actually not bad, but the valve seats were worn badly...Obviously this engine was run on leaded fuel until the 70's...I have no idea when it was pulled from the truck...

[DaveMcLain]

There's no dought that factory valves run on no lead will get chewed up faster than a cast iron seat will, and that both will erode faster as the main seat width is dropped back from about .075" and or the spring pressure is jacked up above 125 psi and or power levels / heat is jacked up from what I have seen!

I have also seen that with out question that running even factory Exh valves in a motor of a car that after a rebuild was run on a tank full of leaded fuel will not see any ware or resession issues if from that point on every other tank full is half leaded fuel!
If your gonna beat the pants off it then you need lead or be ready to pull it down in 15k miles!

What are you talking about? Many times I've seen a factory iron seat that has receded by more than .125 running on unleaded yet the factory valve could easily be reground and re used, no problem. I've never seen the valve itself be effected in any way.

[mag2555]

Sorry , I was referring to heads with induction hardend seats.

[Racerrick]

We routinely install hard exhaust seats on all the old iron heads and in a few flathead blocks. Recently, an "expert" told a customer not to have the hard seats installed, but if he used stainless valves, there wouldn't be any problem with exhaust valve seat recession. What do we know about this first hand?

He is no expert. He is just flatout wrong. Cast iron without induction hardening or seats or leaded fuel will microweld itself to death with unleaded fuels. Stainless valve will even microweld when use on propane engines. Propane motors like Inconel valves and high nickel seats like SBI star series. I got one customer with a 383 11-1 profiler headed propane motor in a big tire 4x4 truck running ferrea super alloy valves that I will see back this fall, I'm curious to see how they did.