backfiring and light colored smoke from my 67 250 sl

[tony1158]

I have been having a problem with backfiring and light smoke coming from my tailpipes on my 67 250 sl.  I have changed points, plugs, condensor, cap, rotor and have corrected timing.  The problem has got better but is still there. It also has a "jerking action" while in second gear. Once I get up to higher speed that jerking action stops.  Can anyone advise? 

[rgafitanu@gmail.com]

Light smoke can be burning oil. Your 67 may have a tube from your intake manifold to the pressure modulator of your transmission (assuming it is automatic). There is a membrane there that reacts to the vacuum in the manifold delaying the shift under open throttle. That membrane gets punctured allowing transmission oil to get in the manifold and cylinders (usually #6). The good thing is that this membrane is easy to change. You can pinpoint to this cause if the smoke is heavier under acceleration and disappears when coasting. I am not sure if this behavior excludes the other causes such as valve(s) and/or ring leaks which are not good.

[Benz Dr.]

If that is the problem, you would see smoke, and I mean lots of it, all of the time. Not likely your problem.

[tony1158]

would back injectors cause this problem?

[Bonnyboy]

the issues may not be connected - make sure there are no leaks from your exhaust -  I had backfires (and rich running, and stalling and...) and it was suggested that it was my exhaust for backfires and maybe other things for the other things - and I had just replaced "most" of my exhaust - guess what - there was another hole in my exhaust causing the backfire - the other issues I had were all unrelated but I was sure they were all part of the same problem.