Had an intake valve seat come loose on my 1953 F600 with a 254 flathead 6 cylinder. Removed head and found the seat loose holding the valve open. Valve, seat and block look ok except for some dings in the block where seat should ride. Does anyone have any ideas or tricks to reinstall or replace the seat with the block in the truck? The rest of the engine looks great and only has about 3k miles on it. Engine was rebuilt many years ago but truck was abondoned outside shortly after. I have been driving the truck somewhat regularly the past year, often at highway speeds until now as the seat came loose, holding the valve open, eliminating compression on that cylinder. Any thoughts on how to make this an easy fix?

 

Boy, I went through that 2 years ago while on a trip with my F5. We managed to reseat it and I nursed it home, about 200 miles. Pulled the motor and tore it down, found that the damage to the seat area was too bad to be able to fix properly, looked into the idea of an oversized seat, but when we got the rest of the engine tore down we found an old block crack repair from a previous rebuild had expanded beyond repair. Bottom line, the block was now junk. I got lucky and scored a reasonably priced rebuilt flathead through another member in Utah. Good luck is all I can say.

 

It is possible to do an in vehicle repair. Biggest problem will be to keep any metal shavings out of the engine while doing the work.
Lots of clean rags and a shop vac nozzle going while cutting the new valve seat recess. And while grinding the new seat. Finding someone local who has a seat cutter (the correct size or oversize) and guides might be the harder part.

 

what about reinstalling the old seat. Believe it or not, the seat came loose a few days before for a short period of time, then found its way back where it belongs. Truck rattled a bit briefly but when seat "re-seated" things were fine for a while. I had been wondering what had happened and realized it when I latter pulled the head. Can the seat be staked or cemented in place? I am getting lazy in my repairs.

 

Based on my experience I would NOT recommend that idea.

 

That is asking for a valve failure, which leads to piston/rod and block failure. Not worth it. Get it fixed the correct way. Pay now or pay later, pretty much

 

It being a flat head side valve engine I'm not over concerned with the patch job coming loose. Worse case the seat comes back out and holds the valve open just as before. The piston can't strike the valve to break it or cause additonal damage as in an overhead valve engine. I would not even consider this in an OHV engine. I am going to try staking the seat. It will cost me a new head gasket and less than an hour of my time. Thanks all for the input. If the seat comes out again I might be looking at a v8 swap if I have to pull the 6. I have a Y-block to T98 bellhounsing in my treasures.

 

Staking has a decent chance if you really clean the recess and insert first. Need the valve out to do a good job. But if the seat pops out, it can cause the head of the valve to snap off, which can then float over to the piston... not common, but I've seen pictures. Stake it good!

 

Finally got time to clean up block really good. Looks bad. Block was beat up pretty bad when seat came out going down the highway. Will be pulling engine and looking for a V8. Other than the valve seat and damaged block, it is a good six with low miles and high oil pressure. I want more power for pulling hills with heavier loads. Thanks to all for the help and advice.

 

Here is a picture of what happened to a 254 Six that I had awhile back when the valve stem broke and went into the cylinder busted the piston and slight score on cylinder wall. just like what Ross has mentioned above. (no seat or at least it didn't come loose)

I have seen were a seat came loose on a v8 and the valve never broke off, just bounced around the valve stem for a long time. (owner must have been deaf or just didnt care to keep driving it like that!

I slid this 254 across the hall to a friend, the bore is 40 over, is your 254 a standard bore?

 

Don't know sure. It is in a retired firetruck with about 7k miles on the truck. The crank was replaced before by the fire department but I don't know if block was bored or not. I have bolted the head back on to keep the boogers out. Will be removing soon. When I get it out I will pull the head again and look.