Valve stem seal skepticism

During my valve rebuild, I also replaced the valve stem seals. Which brings a question: Given the huge amount of reciprocating valve motion this piece sustains and the corresponding stress and wear, and given that it is not held with a fastener or a clamp but just slid over the valve stem and set into a socket, which seems loose to me, how come they don't get slid off out of the socket when the valve is in the upward swing?

My old ones didn't as they were set in the socket pretty firmly, I had to pull them out with special pliers. But I'm just curious what keeps it in place.

 

They should fit firmly into the head. Are you sure you have the correct seals? There is a difference between the exhaust and the intake seals, The intake valve oil seals are white and the exhaust valve oil seals are black. They usually need to be tapped into place with a Special Service Tool.

This is a cross section of how it should seat in the head: It seems yours are not fully seated. Notice the lip that catches in the head.

 

I got an OEM (not aftermarket) gasket replacement kit that came with two bags of 12 seals each. Made in Japan. Seals in both bags were identical, sortof metalic in color. Also, the old seals that came out were all identical regardless of the side (exhaust vs. intake). I did use a special service tool.

 

They should not slide up and out of the head. Reference the picture above. If they are seated firmly you should not have any issues. The white and black thing is from an older service manual.

 

i wasn't observant of the difference because i wasn't aware of it. does it really matter so much as to require doing it all over again ? and can i take the mis-installed seals out and re-install them or does putting them in once mean they can never be taken out and reused? i am asking this because the manual says they are not reusable but i don't know if that pertains only to being used while the engine is running.

 

Not sure what the difference is, but Toyota calls for 2 different types. Maybe due to the temperature the exhaust receives over the intake?

Anyways, I'd make sure it's correct. Going back and having to do it over would be a real bummer.

 

it is also a bummer to spend pretty much a whole day taking 24 valves out and reassembling them if the difference is not that substantial.

 

The cost to Toyota of maintaining and cataloging 2 different inventories tell me the differences are significant.

 

not as much of a bummer dropping a valve or serious blow-by would be

 

Quick research online shows that the exhaust seals are made of Viton, due to heat.

It'll be a pain now for sure, but if the intake seal on a exhaust valve starts to leak oil, EVERYTHING will be coming back apart to replace them.

 

can i reuse the presently installed ones or do i need to get new ones altogether (does putting them in once mean that they can't be taken out and put back in again) ?

 

Should be fine to swap them over if they come out easy. Any force/prying/etc, I'd replace with new.

 

The service manual says that damage could occur if the exhaust and intake seals were swapped.

 

These are the two kinds that I have. There are exactly a dozen of each. I can't tell which fits the light brown vs gray, I'm guessing the left (what I'd call metallic color) is "gray" and the right is "brown"...

 

I would have to agree. When you bought them were they in a package with a part number? That should tell you what is what.

 

The baggy didn't say intake or exhaust...

 

Part Numbers?

 

I think that picture pretty obvious on which one one is which.

Left - Grey
Right - Brown