If my 69 DeVille 472 has been sitting in my garage all night, it will turn over no problem in the morning, but if I've been driving it around for a while and turn it off, it is a very hard start when I try to start it back up. It will turn over once, then take a long pause before continuing to start (almost like the battery is dying). But, like I said, if I let things cool down, it kicks over without hesitation. Anybody know what could be causing this?
The situation you described is not uncommon. You may wish to check the following.
1.) Battery cables. Yeh, sounds basic enough, but the positive cable needs to be a 2 gauge wire in excellent condition with clean connections at both ends. Many aftermarket replacements are 4 gauge, this can cause problems. Also, corrosion can hide under the cable insulation.
2.) Don't neglect the negative cable. It needs to be a 1 gauge wire. Make sure the connection at the frame is solid and clean. Unbolt and sand the contact area to the frame.
3.) Don't forget that grounding strap. The one that connects the engine block to the frame (it is a braided flat wire). Be sure to unbolt each end and clean the contact areas with sandpaper or something abrasive.
4.) Reman starters may have a wire wound armature. The copper bar armature was stock and is the way to go (allows higher current flow when hot). It really makes a difference.
Don't forget these engines require lots of amps for cranking. You need to get the lowest resistance possible in the starter wiring.