Valve seat missing ??

[harmony]

I'm working on a 1946 251ci that is in a run engine stand.  I discovered that it had 4 stuck exhaust valves, so off came the head.  That issue is cleared up now and I decided to pull all the valves, one at a time and clean them up.  Something that I noticed seems odd to me.  But then what do I know, I should mention I think it's been about 55 years since I pulled off a head.  Coincidentally, I think it may well have been the same engine.  I was a teenager and I had bought a retired Bell Telephone service truck.  I think it was maybe an early 50's Fargo if I remember. I had to replace the main bearing. 

Anyways,,,,,  In the picture below you'll see two exhaust valves side by side and you can see the seat on the left valve. but not on the right valve.  But in the next picture with the right with the valve open,  you can see that there is a taper in the block to match the valve.  All the rest of the valves have visible seats.  

Edited March 29, 2023 by harmony

[Jerry Roberts]

That valve seat might be there , just too hard to see . Try cleaning and polishing the area for a better look . And are you sure that is an exhaust valve , I understand that the intake valves didn't have hardened seats .  

Edited March 29, 2023 by Jerry Roberts

[keithb7]

Seen here the upper valve seat has an insert.  It is an exhaust valve. The lower valve seat has no insert. You'l hear people often call them Stellite inserts. They are not. Mopar bought actual Stellite brand exhaust vavle seat inserts and ran a trial of them in their heavy trucks. In the early 30's if I recall. The results were excellent. So the metallurgists at Mopar got to work creating their own recipe for hardened inserts. Then they were there to stay. We all benefitted with them in our cars. When you cut your own valve seats, after doing a few inserts, the bare block at the intakes without any seats feels like butter. It seems to melt away so much easier. The inserts are very, very hard,

 

 

Edited March 29, 2023 by keithb7

[harmony]

1 hour ago, keithb7 said:

Seen here the upper valve seat has an insert.  It is an exhaust valve. The lower valve seat has no insert. You'l hear people often call them Stellite inserts. They are not. Mopar bought actual Stellite brand exhaust vavle seat inserts and ran a trial of them in their heavy trucks. In the early 30's if I recall. The results were excellent. So the metallurgists at Mopar got to work creating their own recipe for hardened inserts. Then they were there to stay. We all benefitted with them in our cars. When you cut your own valve seats, after doing a few inserts, the bare block at the intakes without any seats feels like butter. It seems to melt away so much easier. The inserts are very, very hard,

 

 

Thanks for that, very interesting, So why would all of the rest of the valves have seats?    

[D35 Torpedo]

4 hours ago, harmony said:

I'm working on a 1946 251ci that is in a run engine stand.  I discovered that it had 4 stuck exhaust valves, so off came the head.  That issue is cleared up now and I decided to pull all the valves, one at a time and clean them up.  Something that I noticed seems odd to me.  But then what do I know, I should mention I think it's been about 55 years since I pulled off a head.  Coincidentally, I think it may well have been the same engine.  I was a teenager and I had bought a retired Bell Telephone service truck.  I think it was maybe an early 50's Fargo if I remember. I had to replace the main bearing. 

Anyways,,,,,  In the picture below you'll see two exhaust valves side by side and you can see the seat on the left valve. but not on the right valve.  But in the next picture with the right with the valve open,  you can see that there is a taper in the block to match the valve.  All the rest of the valves have visible seats.  

I bet it does have a seat. It looks like that seat is ground really deep, to the point that it looks like it isn't there. The first pic looks like the valve is quite recessed. 

[keithb7]

The seat is where the valve sits to cool. Although very briefly lol.  The ejecting exhaust gasses are extremely hot. Over time the seats burn up, pit. Can’t seal. They don’t hold up well under the extreme heat. The intake valves remain relatively cool. They are cooled each time fresh cool intake air is drawn into the engine.  They too are cooled when the valve sits in its seat. The valve seat area lasts as it stays cool. No need for hardened insert seats.  Just the exhaust valves need them.  Without them we’d be doing valve jobs alot more often. We would need lead in our gasoline like the Ford & Chev guys.  Yet we don’t need lead additive. Thanks Chrysler for not cutting corners to save a buck and giving us lower maintenance costs. 

Edited March 29, 2023 by keithb7

[keithb7]

 By the 1970’s the rest of the industry started all doing what Chrysler had been giving us since about 1933. See here:

 

 

[Sniper]

A point to mention, Chrysler quit using hardened exhaust seats on engines somewhere between the flathead era and the end of leaded gas.  At least on pass cars, no idea about HD truck or industrial uses.