Don't really see why crankcase pressure per se should cause loss of power,
once the vent port on the inlet manifold or carbs or whatever has been
plugged, and you have vented the crankcase to atmosphere via a filter, which
incidentally is what the oil filler cap on cars without a charcoal canister
does anyway. I'd suspect problems with the ignition or carburetion, which
would be quite independent of any blow-by problems you might be having,
unless the blow-by is so excessive that the loss of compression itself is
enough to cause significant power loss. That would have to be huge, I don't
see why it would come and go, and it would be more likely to blow any number
of seals and gaskets despite the filtered vents. Oil splashing up the vent
pipe and going into the engine either via the PCV and inlet manifold, or
carbs on later cars, is not that uncommon even though its cause can be
difficult to find and cure.
As a 67 you should have an electric tach, if this is still registering
correctly during the power loss and not flicking around you can eliminate
ignition LT, with the possible exception of the condenser. That leaves HT
or fuel. You can diagnose HT problems with a timing light, and if you can
route the cables from the inductive pick-up type into the engine compartment
from the cabin it should be possible to see erratic firing whilst underway.
For fuel you can check delivery by directing a carb feed pipe into a
container and switching on the ignition. It should deliver *at least* one
pint per minute, consistently and with few bubbles. However with an
intermittent problem you may have to run quite a bit of fuel though to catch
the problem. Unless you find a problem that way I'd go through a full check
of valve clearances, plug gaps and condition, points dwell/gap, timing
including operation of vacuum and centrifugal advances, distributor cap,
rotor, and plug lead condition, then set up the carbs for air flow and
mixture balance from first principles. With the exception of points
problems which should show up on the tach pretty-well any of those things
could be experiencing intermittent problems. Also stop when the loss of
power happens and check plug condition, one could be intermittently oiling
up and clearing as oil gets into a cylinder from rings or valve seals. What
*is* oil consumption by the way, and has it increased over the last couple
of years?
PaulH.
----- Original Message -----
> ... Now, my car is having intermittant loss of power issues....
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