Help! Has my engine rebuild gone bad?

[DartSportDude]

Recently, I had the original 340 engine in my '73 Dart Sport rebuilt by a local machine shop. It's a long story, but this was an original engine (in very good running condition) that had suddenly started smoking like crazy after I'd had a repair shop do some work on the car (they replaced the rear main seal and valve cover gaskets). The engine had NEVER smoked before this work was done. I was told the engine had a bad ring, and thus it went in for a rebuild (to a different shop that came highly recommended).

After I got the Dart back following the rebuild, I started the normal break-in process and everything appeared fine for the first 100 miles or so. Then, I started to notice a slight plume of blue smoke from the driver's side tailpipe at cold start-up (this was after the engine kicked down following a minute or two of high idle). I just assumed this was normal for a rebuilt engine. However, the blue smoke became more pronounced over several startups, so I took the car back to the shop that had re-installed the engine for me (not the machine shop that did the rebuild itself).

Anyway, the repair shop says the blue smoke has diminished since they've had the car (four days), and that such smoking is just a normal part of the engine break in. They said I should just drive the car more and see how it goes.

Does this sound right?? The engine did not smoke at all when I first brought it home; why would it be starting now? I'm afraid the shop is just reluctant to tear into the engine to diagnose the problem.

Should I be worried? Thanks for your help.

 

[3404spdvaliant]

Crummy hone job?
Ring gaps not spaced [lined up] from cylinder out of round cause they just dingle balled it instead of rebuilding it therefore screwing you, who knows?
How rich is it? washhhhh

 

[3404spdvaliant]

The only other thing that will have blue smoke coming out of 1 side,
[and run fine] ,would be an intake to valley leak.
So check there first.
And didn't mean to scare ya

 

[DartSportDude]

How would I recognize an intake to valley leak? Thanks for your input.

 

[3404spdvaliant]

Well with the valve cover cap on sealed tight and no breather pull the pcv off and plug it at the carb then wet your thumb and place it over the pcv grommet hole and see if there's suction, might rev it a lil.
Also look at the plugs one at a time.
You can put a vacuum gauge to it also.
Since it's probably one cyl you can't just block the carb with your hand to see if it runs or stalls cause one cyl won't run the engine by it's self.

After that pulling the intake and looking in the ports for the darker oil covered valve stem and runner it self.

 

[71DartGuy]

valve seals?

 

[340sFastback]

Pull the plugs and look at them first. Then do a compression test.

Usually when oil gets in through the intake ports (or intake valve seals) it will do it on deceleration like going down the highway and then letting off the gas pedal; have some one follow you. If should not be smoking more and blue smoke means oil is going into one of the cylinders.

To get the rings to seat you have to step on it some and put the engine under load. Hopefully they didn't put synthetic oil in it.

 

[needsaresto]

Breaking the rings in at full throttle is best done in second or third gear in brief periods of acceleration. Dont go full blast in low gear.

 

[ramcharger]

The angle of the hone pattern has a lot to do with how an engine will break in. The steeper the angle (numerically), the quicker it will break in. A shallower angle will break in slower but add more life to the rings and pistons. Forged pistons also will burn a bit more oil as more clearance is needed to allow for expansion.

At 100 miles I wouldn't worry too much about it unless it fogs the immediate area. Also, make sure this rebuilder will warranty his build after 500 miles passes and be sure you're not running 20W-50 in 60F or below weather. That will kill a rebuilt engine.