Blue smoke, Runs Rough - Blowing oil?

[470]

Check the squish gap (0.9-1.3mm/.035-.051in.) if the top end has ever been removed by others. If within spec. your rings are shot. The wear limit is (0.2mm/.008 in) for piston to cylinder wall clearance.

 

[Linescreamer]

470 - Thanks I can tell you understand rebuilding and trouble shooting these. .008"!!! I probably could barely see the outter edge of the ring with that tight clearance. Just by eyeing it, I can see I have closer to .1". Do these walls wear that easy? Any other opinions here? Lou? Brock? Thanks Guys!

 

[470]

Those spec's I gave you are for oem pistons. Aftermarket pistons (i.e. wiseco, JE) require more clearances. Measure everything and you will know where you stand. Using the proper oil will give years of service. Buying used toys is like opening a can of worms at times. I enjoy wrenching and trouble shooting in my spare time and have seen some pretty shocking things over the years.

 

[Linescreamer]

Just an update and FYI. I bought a rebuilt 657 from SBT and have it back in the ski. Should get her fired up in a week or two. FYI...the tech guys at SBT are helpfull but, you can get allot of different answers and some wrong info if your not carefull. The block also had some thread holes that were.... lets say, not usable. One of the sales guys also sent me the wrong parts and provided very misleading info. I think he is not longer employed at SBT. Just be carefull when ordering parts and asking questions or you could be in for a much longer project then you would expect.