Are my umbrella valve seals correct, who makes the best ones?

[72 Challenger]

Hi everyone,

Maple syrup season is over for me so I'm back to working on my car.

Although it is a 1970 Duster, it has a 340 based 416 stroker with challenger T/A heads.

It smokes on startup. Having removed the valve covers, the guides are all good, no movement in them at all. Bore scope shows oil on cylinder after sitting. 

I'm looking to replace the intake valve umbrella seals.

The motor was built about ten years ago with Chrysler part number 4071003.

Are these correct? who makes the best new umbrella seals? How do you measure these?

I have the spring off the intake so I can measure anything.

I measured my intake valve and got 3.68 so I assume that is a 3/8" valve stem.

Thanks team!

[jimynick]

There's something wonky here. 3/8" stems would measure .375 and if you've got a .368" stem measurement, that's .007" smaller, so if your guide is set for about .3765" to give a .0015 clearance, there's too much clearance and the oil would easily run down the stem and into the chamber. Also, don't just do the exhausts. Think about it, which valve has suction under it and it isn't the exhaust. Umbrella seals should be available from any engine parts store and check a dealer, sometimes they get in the game. In a perfect world, you'd get the heads machined for PC seals and never worry again. Also, check the valve spring compressed height to make sure there's room for the spring to compress as per the cam lift, so that the spring isn't crushing the top of the seal against the valve guide. let us know how you make out and good luck! 

[Brads70]

There's something wonky here. 3/8" stems would measure .375 and if you've got a .368" stem measurement, that's .007" smaller, so if your guide is set for about .3765" to give a .0015 clearance, there's too much clearance and the oil would easily run down the stem and into the chamber. Also, don't just do the exhausts. Think about it, which valve has suction under it and it isn't the exhaust. Umbrella seals should be available from any engine parts store and check a dealer, sometimes they get in the game. In a perfect world, you'd get the heads machined for PC seals and never worry again. Also, check the valve spring compressed height to make sure there's room for the spring to compress as per the cam lift, so that the spring isn't crushing the top of the seal against the valve guide. let us know how you make out and good luck! 

3.680 , I added the zero for ya.    head diameter not valve stem. 

[72 Challenger]

There's something wonky here. 3/8" stems would measure .375 and if you've got a .368" stem measurement, that's .007" smaller, so if your guide is set for about .3765" to give a .0015 clearance, there's too much clearance and the oil would easily run down the stem and into the chamber. Also, don't just do the exhausts. Think about it, which valve has suction under it and it isn't the exhaust. Umbrella seals should be available from any engine parts store and check a dealer, sometimes they get in the game. In a perfect world, you'd get the heads machined for PC seals and never worry again. Also, check the valve spring compressed height to make sure there's room for the spring to compress as per the cam lift, so that the spring isn't crushing the top of the seal against the valve guide. let us know how you make out and good luck! 

3.680 , I added the zero for ya.    head diameter not valve stem. 

What's head diameter? I measured the top above where the retainers hold it to the spring. Did I measure in the wrong spot?

[Brads70]

There's something wonky here. 3/8" stems would measure .375 and if you've got a .368" stem measurement, that's .007" smaller, so if your guide is set for about .3765" to give a .0015 clearance, there's too much clearance and the oil would easily run down the stem and into the chamber. Also, don't just do the exhausts. Think about it, which valve has suction under it and it isn't the exhaust. Umbrella seals should be available from any engine parts store and check a dealer, sometimes they get in the game. In a perfect world, you'd get the heads machined for PC seals and never worry again. Also, check the valve spring compressed height to make sure there's room for the spring to compress as per the cam lift, so that the spring isn't crushing the top of the seal against the valve guide. let us know how you make out and good luck! 

3.680 , I added the zero for ya.    head diameter not valve stem. 

What's head diameter? I measured the top above where the retainers hold it to the spring. Did I measure in the wrong spot?

No, I goofed.... 

[72 Challenger]

No worries, we won't tell anyone 

Thanks for your input everyone, I will go and remeasure more accurately. The engine build sheet says they are stock.

Anyone have a preference on brand?or just keep Chrysler part?