Anybody drop a valve seat ?

[RGC1]

Has anybody else drop a valve seat in your motor ? Dropped an intake valve seat and destroyed a piston. Seems to be a more common thing , ls3 with the 821 head

[102SS]

The valve must have really smacked it to knock the seat loose.

Here is something from the Holden/Caprice forum

https://www.newcaprice.com/forum/viewtopic.php?t=5706

[102SS]

It looks like it happens from overheating the engine.

Different metals different expansion rates.

[RGC1]

Yes different metals and heat for sure. But if you google it you sure seem to find a lot of Ls motors it happens to and more seem to be the 821 and 823 head. This one happened on start up , car was said to be running fine, went into a store , come back out started it up and the crunching started. Found another guy it happened to right on start up after it had been runnng. I bought this SS knowing it had a broken motor.
I have an engine machine shop and we are just rebuilding this ls now had to replace one head bought another head 821 from a business I know that deals in ls motors. The head they had came from a GM crate motor, that went 30 miles and dropped a seat .

Gets me worrying about the ls3 motor I am putting back together currently.
When we put seats in heads we often use a sleeve reatianer and then stake around the seat with a punch to additional tension around the seat.
I do not see where anybody currently makes oversized seats for this head so I won’t be replacing seats but I am staking around all the intake valves in my heads to additional tension to the seat. That is also interesting it seems to always be the intake valves in seats dropping not exhaust.
I am also knocking out the back plugs in the steam holes and will be running four steam lines in my heads over the two from the factory to eliminate any hot spots and detonation in any cylinders.
Also found it interesting the block had no ring ridge ……except the back two cylinders , where steam holes are blocked from the factory.

[102SS]

Originally Posted by RGC1

Yes different metals and heat for sure. But if you google it you sure seem to find a lot of Ls motors it happens to and more seem to be the 821 and 823 head. This one happened on start up , car was said to be running fine, went into a store , come back out started it up and the crunching started. Found another guy it happened to right on start up after it had been runnng. I bought this SS knowing it had a broken motor.
I have an engine machine shop and we are just rebuilding this ls now had to replace one head bought another head 821 from a business I know that deals in ls motors. The head they had came from a GM crate motor, that went 30 miles and dropped a seat .

Gets me worrying about the ls3 motor I am putting back together currently.
When we put seats in heads we often use a sleeve reatianer and then stake around the seat with a punch to additional tension around the seat.
I do not see where anybody currently makes oversized seats for this head so I won’t be replacing seats but I am staking around all the intake valves in my heads to additional tension to the seat. That is also interesting it seems to always be the intake valves in seats dropping not exhaust.
I am also knocking out the back plugs in the steam holes and will be running four steam lines in my heads over the two from the factory to eliminate any hot spots and detonation in any cylinders.
Also found it interesting the block had no ring ridge ……except the back two cylinders , where steam holes are blocked from the factory.

I was doing some reading as well and it seems like most failures happen on start up.

The press fit is only 3/1000 so I guess that is what makes them susceptible to failure after overheating.