Expert: Brad Sears - 4/12/2011

Question
just started rebuilding a 1968 cougar (289). It did not have point/condenser/distributor cap on it when I purchased it. I replaced all plugs/wires etc and got it running but it is running very rough. I checked the spark and found I have spark coming from the cap but the plugs are not firing. Switched plugs and wires on various plugs but no improvement. I found that several cylinders are not firing. Is it timing? Someone mentioned he valves may need adjusting.  Where do I go from here?

Answer
In any situation like this the absolute first thing that I would do is to make a compression test on the engine. This will tell you if the engine has the ability to run smooth and well. If the compression is ok, and the engine still runs rough then the problem is ether ignition or carburetion including a possible vacuum leak. The compression on that engine should be about 125 pounds per square inch to 150 pounds per square inch. Then multiply the highest cylinder reading by .75. The number arrived at should be the lowest reading allowed for the lowest cylinder. Anything lower means that the engine needs to come apart. Trying to chase a rough running engine or a skipping engine without knowing the compression is like chasing your tail. By the way the 289 was not used in 1968, if it is the small V-8 it would be the 302.