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Discussion Starter · #1 ·
Im rebuilding a 1995 7.4 liter 454. The gasket kit I received came with umbrella seals. Are those sufficient or do I need to get pressed on seals? By the way, my stems do not have a place for an oring at the top. Otherwise I would do those and the umbrellas and call it done.
 

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Discussion Starter · #4 ·
Depends on your guide to stem clearance ..what was on there ?
Good question. I can't remember what was originally on there. I recently rebuilt the engine around a year ago and had umbrellas on there, but it turned out the cylinders were out of round and the compression was still pretty low so I pulled it again. When I pulled it there was quite a bit of oil burnt on top of the Pistons and around the valves. I'm assuming that came from the rings not sealing great and not the umbrellas on the valve stems, but I'm not sure
 

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Look at the back side of the intakes. Their stems and guides are always exposed to manifold vacuum. If the stem to guide is loose fitting oil will get burnt on the backside of the intake pretty much regardless of seal quality because the motion of the stem will disturb the seal. Even with umbrellas which shed oil away from the stem clearance rather than prevent it from entering as positive seal does; so with oil flying everywhere some is bound to get under the umbrella and down the guide if the clearance is loose.

Exhaust sees pressure on the stem to guide clearance, the clearance has to be really bad before oil gets down the stem. The problem this causes if it’s happening is it burns on the lower guide clearance and valve stem resulting in sticking the valve so it is late to close or to to just stick slightly off it’s seat.

Bogie
 

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Discussion Starter · #6 ·
Look at the back side of the intakes. Their stems and guides are always exposed to manifold vacuum. If the stem to guide is loose fitting oil will get burnt on the backside of the intake pretty much regardless of seal quality because the motion of the stem will disturb the seal. Even with umbrellas which shed oil away from the stem clearance rather than prevent it from entering as positive seal does; so with oil flying everywhere some is bound to get under the umbrella and down the guide if the clearance is loose.

Exhaust sees pressure on the stem to guide clearance, the clearance has to be really bad before oil gets down the stem. The problem this causes if it’s happening is it burns on the lower guide clearance and valve stem resulting in sticking the valve so it is late to close or to to just stick slightly off it’s seat.

Bogie
Thanks Bogie. I really think the umbrellas are fine. I am 99% sure most of the oil getting through to the valves was from bad piston rings and not bad valve stem seals. I just don't want to have to pull the heads apart on the engine after it is installed if it turns out that those umbrellas aren't sufficient. But my clearances on the valve stems are good and there shouldn't be much oil getting through anyway.
 
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