Post engine rebuild-symptom ?

[NH-75-Z]

Last Fall I posted about my 75-L28, N42/N42 burning oil on

decel, and due to your great advice, I totally rebuilt it this

winter, myself...first time. And its running great..

However, Sat, I took it out for "spirited" driving with the Z car

club, touring So. Vermont rural roads... at lets just say... at

challenging speeds !!

Well its still creating some odor/smoke on heavy decel mode.

like long down hills, and going thru the esses....

Its got new rings, head rebuilt by shop with new valves,seals,

guides were OK . Compression readings after 500 miles breakin

are 160(2) 164(2) and 168 (2) . Manifold vac is 21 at idle.

No oil usage to speak of, maybe 1mm on dipstick in the first

750 miles of breakin, and no break fluid loss, so its not being

sucked into the intake. Otherwise, it running great.

So, what do you think is still feeding the engine to create

the puffs of smoke on decel mode?

More time for rings to seat ?? Oil sucking by PCV ? Its a

new valve. I'm puzzled cause I don't want to be labled the

smoker by the club members following me !!

[ricksaia]

Sounds like rich carbs. But I could be wrong.

[beandip]

How many miles on the rebuilt engine ? If under 1000 miles you should keep the RPM limit to 3 to3500 . After that you should be ok to push it. Just watch the engine temp while break in , at least to 500 miles. Shouldent be a problem after that. This all depends on how tight the engine was set up . I would change the oil after the first 500 miles, filter too. As for any smoke upon decel. , give the engine a chance to brake in and the rings to seat . The worse thing you can do is to run a new engine at high revs if it is tight. Cool your jets a little and enjoy the ride. Both you and your car will live longer.