brownie1,
My first check would be the valves. This would entail a compression check following recommended procedures, then a visual of the rockers and top end. Most carburetion issues involve a certain cirucit in the carburetor and appear at a idle, mid range/high range but usually not through the entire RPM range.
A vacuum leak is another suspect. Make sure the vacuum hose to the distributor is connected. If you squirt carburetor cleaner, propane or anything that will combust into the cracks and crevices around the carb base and manifold to head area you might hear the idle pickup and the engine smooth out. This indicates a vacuum leak in that area.
If the carburetor was rebuilt incorrectly it could have problems too. Sooty plugs are a sign of too much fuel. This could be a float that is set too high or a powervalve that is covered and in the 'go mode' all the time.
Lots of things to check! The compression test would be my starting point...it should pick up a hard mechanical malfunction.
Stuart
Last edited by atomarc; 07/25/2008 3:36 PM.
