Smoking problem

[Unregistered]

A while back I had a clacking noise coming from my Atomic 4. It turned out to be a bent valve (believe it or not) for the #4 cylinder. Since the engine was never thoroughly serviced and I now that I had this valve problem I decided to repair, replace, rebuild and repaint everything possible without removing the engine completely. With the help of my friend Bill who recently retired and sold his Atomic 4 engine repair company, I returned the engine to her original state with almost factory new compression in all cylinders. Everything is perfect on this engine with one exception. Remember the bent valve? Well it looks like I now have a worn valve guide. Lucky me. The engine now smokes at idle and even more when accelerating. I've tried STP additives to the oil to help thicken it and it helped a little. I will try 50 weight oil at my next oil change. Is their anything else I can do short of pulling the engine and replacing the valve guide or could this be something else. By the way the carb was rebuilt and adjusted to factory specs and I even tried to lean it out but she still smokes. Purrs like a kitten but smokes.

[Don Moyer]

Sorry to hear of your smoking problem. Here are a couple of items to check to make sure it's from a defective guide:

1) If the smoke really is oil-based, it would be light-colored instead of the darker smoke associated with a rich condition.

2) Since the guides of exhaust valves normally feel positive pressure from within the manifold during engine operation, any defect in their sealing ability would normally result in sending blow-by into the crankcase (which you're not reporting).

3) If the affected guide were for the intake valve, I would think that you'd see some evidence of oil on the spark plug from the fourth cylinder. Intake guides feel the effects of vacuum within the intake manifold and have the potential of drawing a bit of oil up into the combustion chamber.

If all these things are positive with respect to pointing to a guide, I can't think of anything to do but to replace the guide.

If you have good access to the valve side of the engine, you can remove the head, manifold and affected valve, and even the tappet, which would then make it possible to drive the old guide down (and out), and a new guide in, both from above. To remove the tappet from above, you will have to turn the adjustment bolt all the way to the down position, and then the tappet will clear the top of the valve chamber to be removed.

In the above process, be sure to slip a thin plate of some kind over the tappet hole in the block, so that the old guide doesn't fly down into the crankcase.