Back when I was teaching a 2-year auto mechanics course at a state trade school, one of my students brought his mother's Buick Electra into the shop. It had a 455 engine with a chronic hot start problem. Several shops around town had replaced the battery twice, the alternator three times, and the starter once. The symptoms remained the same- - - -good starting when cold, but slow cranking and/or no start once the engine warmed up. After a 2-hour cool down, the engine would start again. I coached the kid through a "series resistance" test, where the voltage drop across every connection in the starting circuit was measured while cranking the engine with the ignition disabled. Good results- - - -at least until we got to the connection where the battery ground cable was bolted to the engine block. That loose, dirty connection was dropping almost a full volt! 1/10 volt drop at a ground connection is considered to be "acceptable". 5 minutes' work with a wire brush and a new bolt solved the problem.
Jerry
