Which valve stem seals?

[Phil76]

I put a set of 74 heads on my engine, and yes, stupid me, didn't change the valve stem seals before installation. Now I've got smoke on one side, and the #3 plug is wet. So, I'm going to change the seals now, but am having a difficult time figuring out which ones I need. I'd like to get them, in case they need to be ordered, so I can rent the compressor tool, and just get these thing done. Do I need the umbrella type seals, or the positive stop seals with the metal ring? Big difference in price, but I don't want to have to do this again for a loooong time. Thanks

 

[bmc69]

The guides must be machined for the positive locking seals on earlier engines; only later engines used them from the factory. I don't recall the break point year on each series engine but I'm quite certain that the factory '74 seals were the simple floating umbrella type.

 

[ugly74]

If youve got smoke and a wet plug, you may need valve guides, too? 74 uses the regular ol' umbrella seal