1988 F350 460.

The truck would turn the starter very slowly once in a while. Usually after a drive.

So I pulled the starter, alternator, 3 battery cables. Had the starter and alternator check, they passed. Replace the battery terminals on both +/- cables, checked for damage and cleaned all the connection points.

Just did a test drive. About 10 starts after a full warm up (testing the new thermostat housing and other fixes to the cooling system). Sat in 85F heat for about 1/2 hour. Pulled out and did about 10 starts/stops and it was perfect.

Drove about 3 miles, parked at a fast food, when leaving it started doing a slow turn, but this one only lasted about 5 seconds vs the 15~20 that it lasted before, so a big improvement.

So now I THINK it's down to bad cable and/or heat soaked starter.

If I make or buy a heat shield, where would I put it? There's no headers. Would a heat shield go between the engine block and the starter? Maybe a fan that blows across the starter?

Note: I cleaned all the bolts that would connect to the engine in order to get a good ground as well as cleaned the bolt where it grounds from the battery to the frame.

 

The excessive heat comes from the exhaust manifold. The engine only gets in the 200-300F area, the exhaust gets 500-up.

The 460 is famous for the exhaust gaskets leaking and the exhaust manifolds cracking. If there is a small leak, it can puff hot exhaust down in the starter area. If you have a loud exhaust system, you may not hear a small leak. You can test for a small leak by lifting the hood on a cold morning start, start the engine and quickly run out and feel around the exhaust manifold for any exhaust leaks. Of course you have a limited time to do this before the manifold gets too hot. It may take a couple of morning starts to be confident you do not have any leaks.