Have a 75-280 w/90K on her. Starts and runs real good now
thats its tuned and timed. ( have only had it 2 months )
Only problem is that it smokes badly on deceleration, like
coasting down any hill.
Have done compression checks and they range from 150 to
125 to 130 in 2 cylinders, 4 & 6 . Vacuum is 16 .
It does not smoke on start up, so maybe oil is not leaking
down into the cylinders via valve stems.
So do you think its rings?? Blowby??
If so, whats the most cost efficient way to fix? Buy rebuilt
lower end or rebuild by self w/local machine shop to over-
bore, etc...

Z-On ... Gene

 

sounds like valve sten seals to me, especially with the low mileage on the motor. they are fairly cheap and easy to replace. fixed a similar problem on my 78 that way. good luck.