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76 400 four valve stem oil seals

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llessur:
Set about overhauling the engine today, and on the strip down I was surprised to only find four valve stem oil seals on the inlet valves i.e. nothing on the exhaust. I looked at the parts manual and this seems to confirm this. I would be grateful if you could let me know if I am missing something. Thanks and all the best for the New Year

Trigger:
Some valve guides require stem seals and some don't.

llessur:
Many thanks, all the best

Orcade-Ian:
Lots of engines only have seals on the inlets and the main reason is that during the inlet phase when the piston is descending there is a negative pressure within the cylinder and with a worn guide oil can be sucked into the cylinder to be burned with the fuel.  On the exhaust side, the piston is ascending when the valve is open, creating a positive pressure to force the gases out so no oil can enter via the guide.  The small amount of overlap with the valve timing when both valves are open together is usually considered negligible.  Many accountants know about this and delete the seal on the exhaust side.

Ee, the nights are fair drawin' out now tha knows!
Ian

llessur:
That makes sense- thanks. What originally through me was that I had downloaded the Workshop Manual from this site and it shows eight seals, however on checking the parts manual it only shows four.

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