I have an engine problem that has stumped me and I also brought the car to a local "oldtimer" mechanic who also cannot figure out the problem. I have a 1961 292 in my '54 Mercury. I am still running a 6 volt system. I put a "B" intake manifold on the engine and a new Holley Model 4160 465 CFM carburetor. The exhaust manifolds are '54 Ford Police/Mercury accessory duals. The distributor is the stock original. The compression is 140-150 lbs in all cylinders. The points, wires and plugs are new. The point gap and valve lash has been set per specs. The timing is advanced a few degrees beyond the factory 3 degrees. The engine sounds good and has lots of power while driving. There is no noticeable engine miss. The intake tested negative for vacuum leaks.
The problem is a very rough idle. The exhaust coming out of each cylinder bank through the dual exhaust system has a very unusual loud and distinct "put...put...put" sound rather than the usual; soft exhaust pattern of the other Y-Block engines that I have in my two other cars. The weird exhaust "put...put...put" sounds the same coming out of both exhaust pipes. Anyone have a clue as to the cause for the rough idle and weird exhaust pattern? Thanks, Alan S. Freeman