View Full Version : valve seals

10-06-2005, 11:45 AM
New motor,turbo rerouted pvc ported heads Still smokes 162psi on compression test 7to8 psi on leak down test Ive been told that oil is getting into my exhaust & going out the rear If I put in seals in exhaust will that take care of oil getting in there? 400 miles little under half a qrt Motor has about 1100 miles Problem started after hi volume oil pump install Any input would be appreciated Thanks

10-07-2005, 09:35 AM
Sounds like a bad diagnosis to me. Valve seals are not usually used on the exaust valves for two reasons. One, the valves get too hot for most seals- teflon will survive, but those seals have their own limitations. Two, the exhaust port is not under vacuum. At idle, and part throttle, the intake port is under vacuum, so oil gets "sucked" down the valve stem, and burns in the combustion chamber- or fouls the plugs. But the exhaust port is pressurized, relative to the valve covers, and the pressure pushes oil back up the valve stem, away from the combustion chamber.
Maybe the high volume pump is pushing more oil than needed up to lube the valve train, but it's still hard to see why it would go down the exhaust valves, against pressure.

10-07-2005, 10:49 AM
Thanks Ormand, great post. :tup:

Can you expand on the teflon stem seal limitations?

10-07-2005, 11:11 AM
To expand on what Ormand says ...

The seals on the turbo exhaust valves often will get brittle and eventually "grab" the valve stem and then they are yanked out of place anyway (I've seen it now on a couple motor with them installed a few years ago).

I personally don't see the point of putting them on the exhaust valves for all the reasons Ormand listed.

Now ... a couple other things that can cause this:

Excessive crankcase pressure forcing oil past the PCV into the throttle body (you can see this if you pull the doghouse off and see lots of oily residue)
Leaking compressor seal on the turbo (which can be wrosened by high oil pressure/volume on a marginal seal)
Leaking intake valve seals
Bad intake manifold to head sealing. If the heads have been milled, then the angle of the mating surface between the intake and the head might be off ... it can result in the lower lip of the intake (on the block/valley side) to have a gap that oil can migrate to the intake port when it's under vacuum .. like at idle.
Strange enough, a bad seal on the exhaust side of the turbine of the turbo can also cause smoking if it's relatively minor ... above idle, it's hot enough to burn off and not be as noticeable.

10-07-2005, 12:46 PM
Thank you gentlemen Im going to lean towards the 1200 intake gasket The pv valve was sucking oil rerouted it Put a 60 micron filter on turbo to slow flow that helped some If the intake is sucking oil into lifter valley Where does it go from there? Going to redo valve seals & intake later Thanks again