Hercules Engine News

Including Economy, Arco, Jaeger & Thermoil


| July/August 1995



20601 Old State Road Haubstadt, Indiana 47639

This article will deal with the piston and cylinder as it pertains to the 3 inch bore Hercules built engine.

There are several problems that may affect the cylinder bore. These include being badly rust pitted, scored walls, worn out of round and/or ring ridges at both ends of the ring travel area.

Generally, problems with the piston itself are limited to worn ring grooves. Seldom is the piston pin hole or the piston skirt worn enough to cause problems. As outlined later, the piston pin and connecting rod bushing may need attention.

If the cylinder is rust pitted badly enough that it won't hold enough compression to fire and run, there are three choices. You can obtain another block with a good bore from someone who parts out engines. You can have the cylinder bored and refitted with a suitable piston or have the old piston flame welded and machined to size. The cylinder can be bored and sleeved back to the original bore size so the original piston can be used. The latter is what I do. It usually costs about $125 to $150 locally to get that done.

These are times when an 'as is' engine will run fine. When it is taken apart, cleaned up and reassembled, the compression seems to have left. If this happens, it is likely that the cylinder bore is worn out of round. Before disassembly the piston rings had worn out of round, too, but conformed to the cylinder walls. When reassembled with new or the old rings, they no longer conform to the cylinder walls and there is blow by and enough compression loss that the engine won't run or runs poorly. The solution is the same as that mentioned above.