harleyKmodel

Have a newly rebuilt 67 motor that is smoking.Took it apart and found the oil ring end gap to be .050 thousands. maximum allowable is .025 gap Could this be the reason for the excessive smoke?the pistons were covered in oil the head chamber was oily,plugs black with oil on them.I check the timing of the oil pump breather it was correct.Any ides.Also I am looking for a new set of rings,they are S&S pistons #475 and rings .070 over size.also says TRW 494-99 inside the piston

What are the valve guides like? What the clearance stem to guide. Did you use valve seals?

Don't just look at oil control ring end gap. The two compression rings need to be spaced at least 120* apart and the oil control ring upper and lower should be 180* apart. Valve stem clearance and stem seals also important as noted. Check piston to cylinder wall clearance as well. It's down so do it all once.

Rings! Just be sure to order a +.070 set with the same compression ring thickness as the piston ring grooves. New piston, new rings you should not need to worry about ring the piston land clearance.

With everything correct there will still be a break in period to seat the rings. Don't use synthetic oil. Do run the engine for a few 6 or more heat cycles lightly throttling before riding on the road. A few short break in rides with on and off the throttle riding will help seat rings. Depending on how tight you set the motor up will dictate how many break in rides you take. An engine with only .001" piston to wall clearance takes longer to break in than one with 1.5 or 2 thousandths with same piston. Clearance is set depending on manufacturer's recommendations based on piston alloy, forged or cast and intended use. 20,000 mile street use or one night at the track...make sure your cross hatch finish on bore face is correct or rings won't seat. Just couple ideas. Erik K

Thanks all for your advise.I will recheck the clearances and ring locations and install valve seals,the pistons are forged S&S I have put around 300 miles on it carefully.The motor was built by an expert mechanic but it became necessary to disassemble the entire motor.The lower end was reassembled by the original mechanic and I assembled the remainder.I may have done something incorrectly so I have been rechecking all the settings and clearances with the help of a more experienced and trained mechanic.Ill let you know how we make out on this try.

Believe it or not the smoking motor was caused by oil lines being pinched not allowing the oil to return as fast as it was fed forcing oil into the cylinders and causing excessive smoke.Let that be a lesson to you all.Watch how you run the lines.

That's interesting and valuable. I was going to say check the pcv circuit but ....reminds me of a car that came into a shop I worked at. Smoking more than a bunch! The mechanic had the engine rebuilt. Still smoking. I went over and took a look. How's the PCV system? He pulled it apart and I took a look. Shook the valve, no rattle. Looked inside and the entire guts were missing. Rusted away. Oil was being sucked into the intake manifold directly... Erik K