My El Camino has had this problem for some time, but for some reason, I've never thought to ask this question at CZ28.com. It occours more often when the car has gotten thoroughly warmed up, but it does it when cold as well. The starter will crank just fine for one or two revolutions, but then it will suddenly make a loud crashing sound, almost as if someone is jamming a screw driver between the flywheel and starter gear. When it makes this sound, the cranking pauses until the sound quits. I replaced the starter and flywheel (which was cracked), and it started flawlessly for a while, but it started doing it again when I had rebuilt my engine and put everything back together. I took it to a shop (I was out of ideas) and they said the starter gear was not coming close enough to the flywheel to maintain engagment, which sounded reasonable to me. So they ground a little metal off of the starter's mounting area, and it seemed to work very well. But it was only a matter of time before it went right back to making the sound again. It is the correct starter for my flywheel. I have asked many people what it could be, and no one has any ideas. I was hoping maybe someone here might.

 

If it was an auto trans car I would say you had the flexplate on backwards but that's tough to get wrong with a flywheel! Is the starter spur gear not coing out far enough to fully engage the flywheel teeth? Or is it that the teeth are comong out far engough but just touching at their tips? Actually lay under the car while someone cranks and watch the engagement. The spur gear shoud SNAP out, mate with the flywheel teeth (going on at least ~1/2", with teeth deeply engaged with eachother) and the starter will immediately start turning.

Thinking outside the box.... Is it possible the wire from the ignition is losing current intermittently? This will cause the solenoid to disengage momentarily and then kick back on while the spur gear is still turning and give that sound you get if you try to start an engine that is already started- GRIND!! If so, it could be a bad ignition switch, a short, a marginal connection, or just that your stock starter wire (the little one, not the battery cable) just can't carry enough current from the ignition switch to keep the solenoid energized. Happens on older cars with stock wiring and headers sometimes- lots of heat around the starter and it's solenoid and wiring. A hot start kit might be the fix if this is the case.

Also, is it possible the engine is kicking back against the starter? This is common with a hot engine and a high initial advance setting on the ignition timing. That can cause some nasty noises, too.

How's that battery cable? Not just the one to the starter, but the negative that grounds to the engine as well. 30 year old cables are always supect, even if they look externally good.

 

This actually seems very likely. My battery cable is brand new, but most of the ignition wiring is original, and my car doesn't have the best electrical system. Now that you mention it, the sound does resemble that of a starter trying to turn a running engine. The wiring directly attached to the starter is all new (I have a quick-disconnect harness), but from there back, it's all 30 years old. I think I will check all of the things you mentioned as soon as I can. Thank you very much for your help!