V8 Engine Problem

[Matthew Beaubien]

Dave,

>I bought it, now at 125k.  Ned's chip, other engine and exhaust stock.

>Good compression all cylinders (and w/in 10%).  Cylinders 2, 3, and 8 have
>significant leakdown, and can hear air going into crankcase on those
>cylinders.  Plugs 2, 3, and 8 show a little more brown deposits than the
>others.

What sort of leakdown numbers are we talking about? 5%? 10%? 40%?  None of the plugs have black deposits from burning oil?  Could indicate that the exhaust valve guides/seals are shot, and the oil is entering the exhaust port and not the chamber.

>1)  Leakdown can't check oil rings because they have different angle to
>cylinder walls when engine is running.  Also, ring gaps could be lined up.

Leakdown and compression tests can't tell you anything about the condition of the oil rings.  You can have great compression and leakdown numbers but still burn lots of oil if the oil control rings are gummed up.  Ring gaps that are lined-up will not produce "significant leakdown" values.

If the oil rings are gummed up (chances are they're fine given synth oil and regular changes) you could conceivably free them and have it run fine.

If the chip has caused any detonation, you could have broken rings/ring lands etc.

Hope that helps.

Matt Beaubien
'86 5kt
'73 911E