Hard starting 350 Chevy engine, what could be the issue?

Question:

l installed a 350 Chevy engine in my 1969 Firebird. The cylinders were bored .030-inch over and the engine was rebuilt. I am delighted with the performance, but the engine is hard to start. The starter fights to get each piston to the top of its compression stroke and the engine stops rather abruptly when the ignition is shut off. I had the battery load-tested, set the ignition timing, adjusted the valves and cleaned the block ground-strap connections. I have put about 400 miles on the engine and the temperature runs from 195 degrees to 205 degrees. I’m worried the short block is just too stiff. Do you have any suggestions?

Answer:

It is possible the piston-to-cylinder wall and/or bearing clearances in your engine are too tight, but I suspect your problem lies elsewhere. The engine would not have carried the car 400 miles if the bearings were so tight as to prevent the starter motor from turning over the engine. If the piston to cylinder-wall clearance is too tight, I would expect the engine to run quite hot and the temperatures you describe are not excessively hot. My first suggestion is to make sure the battery cables are properly sized and in good condition. Check the cable ends for corrosion and broken wire strands. Make sure the cables are fastened securely.

Have the starter motor tested by a competent shop. In addition to a bad starter-motor solenoid, many internal starter-motor problems — including a bent armature, bad bearings, loose pole-shoe screws or thrown commutator bars can result in the situation you described. Many “newly rebuilt” starter motors only contain replacement parts for previously broken components; marginal but-functioning parts are sometimes reinstalled.

If the electrical circuit and the starter are OK, you may indeed have an internal engine problem. In addition to tight clearances, high compression can cause the problem you described. Higher compression can be caused by excessive milling of the block deck surface or cylinder heads or an incorrect combination of pistons and cylinder heads.