Valve seat recession on iron heads and stainless valves

[Olefud]

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?

Just a sample group of one, but way back I ran my 1300 Alfa on “white” Amoco gas and ultimately lot a hunk of a valve.

[ZEOHSIX]

Induction hardened exhaust seats came in to being around 1971 on GM cylinder heads. On earlier heads I always specify hardened seats as my motors are used in high RPM applications and you will see rapid degradation of the seats in this type of useage. I see "Internet Experts" on car boards all the time proclaiming you don't need hardened seats.....have yet to find one of these "Gurus" who has ever worked in a Auto Machine Shop......

[DaveMcLain]

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?

Just a sample group of one, but way back I ran my 1300 Alfa on “white” Amoco gas and ultimately lot a hunk of a valve.

Leaded gas for motor fuel didn't really come into widespread usage until the 1950's. Remember that Phillips 66 didn't mean Route 66 it meant 66 octane. Union 76, oh boy!

[novadude]

Isn't preventing recession more about heat management? I might me completely wrong, but I thought that the recession was due to high temperatures "micro-welding" the valve to the seat and pulling small amounts of material from the seats a little bit at a time. If that's true, can't you control this with tight guides, proper seats machined concentric to the guides, and a good tune to keep exhaust temps down? I'm talking about a street cruiser or bracket car, not a truck pulling a horse trailer up a 3 mile grade.

[PackardV8]

Isn't preventing recession more about heat management? I might me completely wrong, but I thought that the recession was due to high temperatures "micro-welding" the valve to the seat and pulling small amounts of material from the seats a little bit at a time. If that's true, can't you control this with tight guides, proper seats machined concentric to the guides, and a good tune to keep exhaust temps down? I'm talking about a street cruiser or bracket car, not a truck pulling a horse trailer up a 3 mile grade.

Yes, for true; valve seat recession became increasingly a problem when trying to meet all the emissions and mileage requirements, OEMs began to lower compression and retard ignition and run operating temps higher and lower gear ratios to increase fuel economy. The result was even small cars operating like a truck pulling a horse trailer up a 3 mile grade.

[benno318]

I see "Internet Experts" on car boards all the time proclaiming you don't need hardened seats.....have yet to find one of these "Gurus" who has ever worked in a Auto Machine Shop......

so true...

[Racerrick]

Isn't preventing recession more about heat management? I might me completely wrong, but I thought that the recession was due to high temperatures "micro-welding" the valve to the seat and pulling small amounts of material from the seats a little bit at a time. If that's true, can't you control this with tight guides, proper seats machined concentric to the guides, and a good tune to keep exhaust temps down? I'm talking about a street cruiser or bracket car, not a truck pulling a horse trailer up a 3 mile grade.

If you granny drive it or it a show and shine car they will last awhile. If you beat on it, they are done in no time. In the end it easier to put seats in it and have some piece of mind.

[Morgo]

Few years ago I done port job to Chevy 4,3 V-6.Little later guys come back and complainend the exhaust valve job.Then I came aware that this was a boat motor;just few hours of running and seats were shot.Customer understand when I showed how where there is a water channel close the seat it was as cut.Where there wasn't water close the seat was...
Boat engine running flatout hours is a bit different situation than driving around the town about idle.

[modok]

I was thinking about it a bit more.
There probably is a bit of material transfer between valve and seat. Stainless is protected from erosion by forming chrome and nickel oxide on the surface, and maybe that oxide transfers to the seat as well.
If you had a valve with 4% nickel instead of 2%, maybe it would be slightly improved?

[racear2865]

I was thinking about it a bit more.
There probably is a bit of material transfer between valve and seat. Stainless is protected from erosion by forming chrome and nickel oxide on the surface, and maybe that oxide transfers to the seat as well.
If you had a valve with 4% nickel instead of 2%, maybe it would be slightly improved?

We disassemble heads ever day in my shop, both stock valves and stock valves. And I dont care what valve is in there, there is some recession but the biggest thing I see is deformity of the seat. Take the valve and clean seat and valve well, then lap just to see the seat. Then you know why you needs seats or not.
reed

[KnightEngines]

Maybe I'm the only one, maybe our fuel over here is different - but I don't use hardened seats unless I have to & I don't see the massive valve seat recession pointed at here.

A few months ago I pulled down an engine I built in 09, competition engine, road race, heavy use every time it gets fired & running on unleaded pump fuel.
Heads are early 70's iron, no induction hardening & I had fitted 1.625" exhausts - factory is 1.47".
The exhaust seats only needed a light dust with a stone & they were good to go.
Valves were ferrea 6000.

This isn't the odd one out, it's more the norm.

I do fit hardened seats for engines to be used for daily drivers & big milage, but for performance stuff it seems to me that by the time the seats need work the whole engine is due for a freshen & even then the seats usually just need a touch up.

[Circlotron]

How were things done in the model T era with no lead in the gasoline? Did they have hardened valve seats?

[user-23911]

Going back 30 odd years when CNG was popular here, the trick was to use "moreys upper cylinder lubricant " with a special dispenser system that ran on vacuum.
You'd get a mist of oil in the intake manifold which lubricated the valve seats etc, that was for older engines designed for leaded petrol.
Model T fords.......they probably had oil in the intake too?

As far as "stainless" goes.......it's just a name. It won't rust?
Valves are always some sort of fancy alloy of various metals......like inconel.

[Carnut1]

Maybe I'm the only one, maybe our fuel over here is different - but I don't use hardened seats unless I have to & I don't see the massive valve seat recession pointed at here.

A few months ago I pulled down an engine I built in 09, competition engine, road race, heavy use every time it gets fired & running on unleaded pump fuel.
Heads are early 70's iron, no induction hardening & I had fitted 1.625" exhausts - factory is 1.47".
The exhaust seats only needed a light dust with a stone & they were good to go.
Valves were ferrea 6000.

This isn't the odd one out, it's more the norm.

I do fit hardened seats for engines to be used for daily drivers & big milage, but for performance stuff it seems to me that by the time the seats need work the whole engine is due for a freshen & even then the seats usually just need a touch up.

I bet you pay strict attention to your guide clearances. I do and I think this is the real secret to seat life. Thinwall bronze and correct clearances with a good tune need no inserts or lead. Inserts are nice if the heads have the meat but I have never had seat recession issues, when I disassemble and the seats are shot the guides are also shot. I needed to grind down a set of 1.94 Ferrera stainless valves to 1.7 to patch up a Chevy 250 my brother once had. The stock exhaust seats and guides were so bad this is how big I needs to go just to put a seat on it. Thin, but the rest was stock with some porting. He loved it. Thanks, Charlie

[Truckedup]

Going back 30 odd years when CNG was popular here, the trick was to use "moreys upper cylinder lubricant " with a special dispenser system that ran on vacuum.
You'd get a mist of oil in the intake manifold which lubricated the valve seats etc, that was for older engines designed for leaded petrol.
Model T fords.......they probably had oil in the intake too?

As far as "stainless" goes.......it's just a name. It won't rust?
Valves are always some sort of fancy alloy of various metals......like inconel.

Model T Fords? Model T was introduced around 1912? Tetraethyl lead was first used in gasoline around 1924 and likely not common to all gasoline in the USA until mid 1930's ?