Hit 1,000,000 miles on my Series 60, now I'm second guessing the rebuild

Rolled over 1,000,000 on my Detroit Series 60 last Tuesday out on I-80 near Rock Springs. Original bottom end, never had the head off. I've been planning a full rebuild for months, got the kit sitting in the shop, but now I'm wondering if I should just run it until it quits. My old timer buddy says anything past 800k is borrowed time and I'm an idiot for even thinking about it. Another guy at the fuel stop says those old 60s will do 1.5 million if you don't hammer them. I know the oil pressure is still solid at 55 hot idle, but the blowby is getting noticeable on cold starts. Anyone else hit a mileage number that made them rethink their whole maintenance plan? Did you pull the trigger early or ride it out?

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1 Comment

taylor.hayden18h ago

Blowby on cold starts is the tell right there, that's the rings starting to let go and it only gets worse once it starts. That oil pressure at 55 hot is still good, but a million miles on the original bottom end means every bearing and liner is at the edge of its life, not the middle. Run the rebuild now while you're parked in the shop, not when you're broke down on some pass at 2am with a load that's already late.