470 quits abruptly

"I have a 1989 470 and alpha o

"I have a 1989 470 and alpha one. About 3 weeks ago at about 3,000 rpm the engine quit abruptly. Just like someone shut the key off. But it wouldn't turn over and re-start for about 5 minutes. Once re-started, it ran good and started good, hot or cold, untill yesterday, when it happened again. Quit abruptly after about a 5 minute run at 3,000 rpm, and the engine wouldn't turn over for about 5 minutes, and then it turned over slowly, finally started, and ran good and started good all day long. Ran good and started good all day today.
Any ideas?"

"Check all of your grounds/bat

"Check all of your grounds/battery terminals for any corroision/looseness and also check the main wire harness plug on the engine.Undo the clamp, disconnect and spray some contact cleaner on both sides of the plug."

Make sure you keep an eye on t

Make sure you keep an eye on the basics. Does it have good oil pressure through one of these events? Is the engine temp spiking? Sounds a little like it's seizing due to temperature... in which case it would free itself up and restart once cool. Water pump working properly?

"Oil pressure is 60-70 psi @ 3

"Oil pressure is 60-70 psi @ 3,000 rpm, temp is 160 deg f constant. I think it is electrical, because it stops so suddenly. A seizing engine will gradually slow down and finally grind to a halt. I can't figure out why it turns over slowly when it quits. I will check all electrical connections again."