I built a stroker engine for my '71 Z. Hatch Engines built the bottom and and I put the head together. The valves were also done at a machine shop. It ran perfectly for two years. Engine has 1500 miles on it. I show it occasionally and rarely drive it. I started it a while back to get some fuel in it. I looked in the mirror and saw a lot of smoke coming from the tail pipe. I drove it home and it stopped smoking after driving it for 15 minutes. Today I took the car in for some electrical work. Same think happened. Smoked badly at first and then stopped smoking after I drove it across town.

The engine runs well and is responsive. Where is this oil coming from? I wonder if it is leaking down a valve stem? (I did install new seals) Anyone have any ideas?

Edited October 7, 201014 yr by ZSaint

1500 miles ? that motor hasn't broken in yet so your rings might not be seated or are sticking.

We used cast iron rings and the engine is broken in. It did not smoke for two years and now it started smoking. Why the change?

Pull the plugs and see if any are oil fouled.

Could be a bad seal that's allowing oil to leak past on a stopped motor.

When was the last time you changed the oil?

If you're running rich and gas is diluting the oil, the change in viscosity could explain more of a leak past the seals.

I am using Mobil 1 synthetic oil. Ran 30W oil for 600 miles to break it in.

I think you are on the right track. I can start it and let it run for a couple of minutes to get the oil "burning". I will then check out the plugs for 'oiling'. I have all of the equipment to pump up the cylinder that is suspect. I will pull the springs off and check the valve seal. I will probably replace them anyway just to make certain they are new.

I do remember some of the valve seals did not "stick" to the guide very well and needed some extra attention. I hope one of them popped off and is sucking oil into the chamber. I'll go to work on that.

Anyone else have a theory? My brake fluid levels are staying the same so it is not suckin fluid into the manifold. I think the valve stem seal is the way to go on my search.

Never break in a new engine on synthetic oil, the rings wont bed in properly.

There is a thread on hybrid Z about using a ford type of valve guide seal that is supposed to be very good if the problem is in fact valve guide seals. In my expierence with my engine it was not fully broken in till about 5 thousand miles. I also used cast iron rings but never used a synthetic oil,but if I was I still would not use it for at least 5 thousand miles, it's just too slippery for a new engine.

When I read over your original post again i got to thinking if it smokes for a short time after starting the engine wile hot it has to be valve guide related, oil is dripping down past the valve and pooling up on top of a piston. It's probably only one cylinder doing it or maybe the seals were not installed properly. Or maybe thier just dryed out and need to be replaced, not uncommon for a car not drivin regularly.

Before you do anything - change the PCV valve... that's the most usual cause of your symptoms, once the rings seat.

11810-E3000 Assy-Control Valve Crank Case Emission.

FWIW,

Carl B.

Edited October 9, 201014 yr by Carl Beck
corrected part number

Before you do anything - change the PCV valve... that's the most usual cause of your symptoms, once the rings seat.

11810-E3100 Assy-Control Valve Crank Case Emission.

FWIW,

Carl B.

So right,totally forgot about that.

There is a thread on hybrid Z about using a ford type of valve guide seal that is supposed to be very good if the problem is in fact valve guide seals.

Did you use a higher lift cam? If so did you check retainer to seal clearance? If not, your retainer could be pounding on your valve seals......any cam over .475 lift could cause a problem. The above Felpro seal that Zforce mentions would solve the problem (the seal is shorter than stock for increased clearance). Jon Mortenson has a good thread on that exact problem. Probably isn't your problem, but something to think about. Guy

Edited October 8, 201014 yr by Arne

http://www.classiczcars.com/forums/showthread.php?t=37053

Read this......but once again, it's probably not the problem if you drove it for two years with no problem. PCV valve is a much easier fix. Also, when there is a lot of humidity in the air, your engine can have the appearance of smoking, when it's just condensation burning out of your exhaust system (clears up in 5 or so minutes). Check your plugs for oil if not PCV. Guy

I seriously doubt the engine is truly broken in at 1500 miles. I too believe synthetic oil should wait until the 5000 mile mark, but mostly, I believe the valve guide seals are giving the grief. The have dried out and now the synthetic oil is so slippery it goes right past the seal. My 77 smokes on start up if parked for any length of time, but only does it with synthetic oil in it. Changed back to 10/30 Valvoline and it went away. (did this on the advice of my machinist). Typically, start up smoke comes from oil seeping down the valve stem and pooling in the cylinder and burns up. Smoke from ring issues usually comes when letting off the throttle after hard acceleration or after coming down a long hill using the engine for braking (letting off the throttle). When getting back on the throttle if it really blows the blue smoke, it typically is ring related.

As a side bar, synthetic oil pours out the seals of my 57 international but conventional oil stays put.

My experiences