Assignment for class

[ShawnAzzopardi]

Right, so I have an assignment for auto class due tomorrow and I only have one question left to do, and I couldn't find any info on it online so I figured I'd ask you guys if you could shed some light on it please

So the question is, "Give reasons why on some engines, only the inlet valves are fitted with valve stem seals?"

Can anyone help please?

[total_vauxhall]

Due to the fact that when the exhaust valve is open, there is pressure pushing out, which means that it is pushing the oil out of the runner. This means there is no point in sealing the valve from oil seeping down.

Also the small bit of oil that seeps onto the valves help cool them.

Could be wrong

[Stuart]

Due to the fact that when the exhaust valve is open, there is pressure pushing out, which means that it is pushing the oil out of the runner. This means there is no point in sealing the valve from oil seeping down.

Also the small bit of oil that seeps onto the valves help cool them.

Could be wrong

This, cut print win :D

[total_vauxhall]

Too right . is it correct ?

[Stuart]

sounds feesable

Bit like how turbo oil seals arent "seals" in the traditional sense that we know, but a set of grooves machined into the housing and shaft that give the oil pressure some gradient so that the exhaust gas keeps it pushed back (or something to that effect, maybe... )

[kevy.m]

Here's my input............

I would say this is pointed towards ohv engines........

The exhaust valve gets cylinder pressure rather than vacuum & if there was a seal it would suffer from sticking valves over time
as the seal stops the lubrication, the extra heat on the exhaust valve will burn away any old deposits allowing the fresh oil do its job.


Me thinks

[ShawnAzzopardi]

Thanks for your replies, we'll see how I did when the results come on :D