I have recently been getting some black smoke out of the exhaust on my 1950 248ci. I checked the carb and it seems to be OK and adjusted correctly. Fuel pressure seems good. The ignition also seems correct. I removed the valve cover to check the rocker arm adjustment and I ran the motor to watch them. I noticed that several of the push rods were spinning while it was running. Has anybody seen this or know what causes it? Is it OK? I thought the springs might be weak in the lifters, so I ordered new ones. Any comments or suggestions (Good or Bad) would be welcome.

Thanks,
Mark

Mark,
Actually, all of the pushrods should be spinning. The lifters spin as they run on the camshaft, so the pushrods do the same. If some of them are not spinning, it could be a sign of the camshaft beginning to wear badly.
Hope this helps,

Thanks Bill! Could they be adjusted to tight?

That would not keep them from spinning, it would just hold the valves open.

If you get black smoke when when you start the car (cold), that would point out to excessive oil leak thru the intake valve stems. Also, the spark plug electrodes would show a black oily mark on the intake valve side.

are your plugs carbon fouled, (black fluffy buildup)? if so your air/fuel mixture could be running too rich. carbon fouling is also caused by too much idling and not enough driving, you know working on the car and idling to check things, but not actually getting it on the road. both can cause that black smoke.

Jyrki, the engine is newly rebuilt (new pistons, rings, bearings, valves & guides...)

http://home.earthlink.net/~56fireflite/sitebuildercontent/sitebuilderpictures/buickengine.jpg

so I doubt that's it.

Chubx2, I drive the car A LOT . and I've tried messing with the Carb mixture but it only gets worse (not better) so the carb is possibly bad but it looks OK.

I only see the black smoke when I push the accelerator and something new that I noticed today is that when I'm driving the car on the X-way I can control the amount of vacuum with the gas pedal!! So I'm really leaning towards a new vacuum advance...

http://home.earthlink.net/~56fireflite/sitebuildercontent/sitebuilderpictures/p1010001.jpg

Mark,
It is normal for vacuum to change as you press on the accelerator. I doubt that it has anything to do with your vacuum advance. Black smoke means too much fuel.

Let me clarify. As I step on the accelerator I can watch the vacuum guage go from 19" @450rpm down to 0" @3000rpm and stay there until I almost completely let go. I can hold the guage at any increment (5,10. etc.) by keeping the gas pedal steady. That's why I figured there must be a leak in the advance line or somewhere in the carb.

Mark,
That is normal. When you open the throttle, the vacuum reading will drop to "0" at wide open throttle It will read full vacuum, in your case 19" at closed throttle, and otherwise somewhere in between depending on the load and throttle position. That is how the vacuum advance works. When you are at wide open throttle, it has "0" vacuum and retards the timing as much as it can. At light throttle and load, it will have close to maximum vacuum and will advance the timing fully. In between loads and throttle openings will vary the advance accordingly.
So ... the vacuum readings you are getting are normal.
I remember cars with vacuum operated windshield wipers. The wipers always would slow way down going up hills, the low vacuum was the reason.
Your black smoke problem sounds carburetor related.