On Fri, 28 Jun 1996, STUART BOLLEN wrote:
> My friend had his motor recently rebuilt by a local racing shop, and
> they blanked off the crankcase breather hole, said it wasn't
> necessary. The car is blowing smoke, and they say its only because
> the rings are not yet seated. I think its crankcase pressure.
> Interested in people's opinions.
Did the shop bore and hone the old wet sleeves? If so, the rings should
seal well enough right out of the machine shop to prevent major blowby.
If there is significant blowby, then either the job was botched or the
shop is one that still believes in honing to a dead-smooth finish. If
the latter, then it could take the rings a very long time to seat.
It sounds like someone in the shop doesn't understand the function of the
lower breather. The tube extends down beneath the car, where the
airstream past the end of the tube creates a slight vacuum in the tube and
therefore in the crankcase. This draws air in through the oil filler cap
vent, through the crankcase, and out the lower vent tube. The air flow
carries vapors out of the crankcase. Those vapors include volatiles and
moisture, both of which would contaminate the oil if they remained. It
isn't as effective as a modern closed system, but without it the engine
will sludge up very quickly.
Tell your friend to re-install the lower breather tube, and if there is
still significant blowby after a couple hundred miles, find a new machine
shop.
-----------------------------------------------------------------------
Chip Old 1948 M.G. TC TC6710 NEMGTR #2271
Cub Hill, Maryland 1962 Triumph TR4 CT3154LO (daily driver)
fold@mail.bcpl.lib.md.us
If cars had evolved as fast as computers have, by now they'd cost a
quarter, run for a year on a half-gallon of gas, and explode once a day.
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