Smoking is not unusual on a new rebuild. Oil smoke usually cures itself on
break-in. A break-in of 500-2000 miles may be required for the rings to wear
in and seal properly. Assuming your machine work was good, and assembly &
parts were correct, I'd proceed with the break-in and watch for continuous
improvement of the smoking. Use a good quality motor oil (not synthetic!) for
the break-in; change it according to local wisdom (once at 250 mi, and once
again during break-in, or whatever your theory might be. You can't change it
too much during this time, but folklore varies on the right intervals).
Changing the oil during break-in is important to remove any tiny metal
particles that are wearing off and circulating in the oil.
The reason you don't want to use synthetic oil during break-in is that it is so
good at reducing friction it takes forever to wear in the rings to a good seal
-- it'll just keep smoking for thousands of miles! After you are satisfied
with break-in and the smoking is over with, you can switch to synthetic oil if
you like. But only do that if all internal seals were changed during your
rebuild -- synthetic oil is not compatible with some old seals.
Also, during your break-in OCCASIONALLY rev up the engine pretty good to keep
from wearing in a low ridge in the cylinders, at the top of piston travel.
Running at high revs stretches the rod and takes the piston to it's farthest
travel; you don't want a ridge worn lower than that, cause sometime you're
gonna get on it and extend the piston past the low-rev height. If the rings
bang into a low ridge they're going to suffer - badly. But don't gun it a LOT
during break-in either-- just baby it along with occasional hi-rev sprints and
you'll be fine.
Hopefully your engine will wear in with a short break-in and quit smoking. If
not, start looking for mechanical problems or other sources of smoke.
--- Guy <Guy@weller-lakes.freeserve.co.uk> wrote:
> Why does my newly rebuilt engine smoke so much ?
> Will it get better, or have I put it together wrong ?
> Rebored +30, new pistons, new most of everything else.
> UK spec 1275, no smog stuff.
> Standard breather pipe from front timing chain cover to Y branch at
> manifold. Twin SUs Done 6 miles.
>
> Guy
> 1500 Midget
> 1275 Sprite
>
>
===
Michael B. Dietsche, P.E.
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