I just recently changed my oil from 30w to 10w-30, and installed a new flowmaster exhaust system. The motor was just built last summer, and has about 500 miles on it. After I got done the car started to smoke. A big puff at start up, and then a steady small amount after the engine warms up fully. I rebuilt the carb, put in a new PCV valve, and pulled and resealed the intake. When the intake was off I noticed oil on top of the valves. So naturally I’m thinking valve seals. My question is can the 10w-30 be leaking when the strait 30w didn’t? And if not then what could cause all the valve seal to fail at once?

If you guys have any ideas I would appreciate it. I’m fresh out.

Unless the guides have been machined for pc seals,I would expect the slip on seals to get beat up pretty good.

go back to 30wt, see if it goes away.

Unless the guides have been machined for pc seals,I would expect the slip on seals to get beat up pretty good.

What would cause them to all fail at the same time, and so fast?