In December I purchased a 1971 Chevelle, 454SS, 4 speed that had sat
for 7-8 years in Florida. I am just now digging into the car but have
a problem I can't solve. The car has been set to specs in timing and
dwell, has new points, plugs, wires, rotor, dist. cap and coil. The
car at first had a hesitation whenever you pressed on the gas but ran
better at higher speeds. The car would run real rough when you came
off the freeway and at a stop sign, the car would vibrate and shake.
Yesterday it began to run even rougher, got out the timing gun and
made sure dwell and advance were correct. Problem is that the timing
line always used to be easy to see (remained steady under the light)
and set but now it is fluctuating a lot and getting the line to sit
still at 8° is almost impossible. Before I find someone to take it
into, I thought I would see if anyone has any ideas or it these signs
point me in any direction. I know there are a lot of variables.

Thanks for any help you can provide.

Sometimes, not always, but sometimes, a fluttering timing mark is a sign of a badly worn timing chain. You can pop the cap off and move the engine back and forth by hand to check and see if there is any slack by observing the rotor. If you can move the crank any significant amount without observing any movement by the rotor, chances are, the timing chain is stretched and will need to be replaced.

Also, it sounds like a compression test is in order.

71454
Betcha anything you have bad gas, after sitting 7-8 years things happen. Water in your humid climate + varnish build up and on and on and on. Probably best to clean out your tank, lines,replace filters and dig into the carb and really clean it up. I recieved a dose of gas with small gritty dirt like things that made it thru my ~glass~ "i dont use GLASS no more filter and my car just ran like crap until the carb came apart and cleaned OUT. Good luck and please let us know what you found.

Jim

A fluctuating timing mark indicates a worn distributor shaft. This will cause the timing to jump around.

I'll go along with Jim on this one. I'll bet your fuel delivery is the problem. Go through the carb and then put a good filter to catch any more debris and then add some good gas and see what happens..

RandyB..

Check your filter later on and see what it catches..