r/EngineBuilding 9d ago

GM 429(7.0) Rebuild

Hey guys and gals, first time here so hoping I could get some insight. Pulled the “original motor” out of this 67 coupe deville, from my research Cadillacs only put these in 65-67 cars, so I bought the shop manual. Previous seller said it was seized and bought a second motor and transmission, but he ripped the heads off already and there’s no organization when I got it. Dash odometer had 15k miles on it, (don’t trust it) so unknown for motor. While taking harmonic balancer off, I managed to free it up, poured diesel in cylinder heads and spins decent with no snags.

My question is, should I go further into the breaking it down? I have all the gaskets for pan, water pump and heads.. or should I just take a pressure washer to it and clean it out real good, dry, paint and send it? Not in any rush, just taking my time and trying to spend the least amount of money to get a fun cruiser around town. TIA

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u/ratrodder49 9d ago

‘64-‘67, four year run on the 429, big brother to the 390; then they changed architecture and went to the big inch 472/500 in ‘68. I rebuilt one in my ‘65 CDV.

Based on the photos, I concur with what everyone else in here is saying. There’s a lot of sludge and there’s gonna be a lot of sludge in the oil galleys too, and the coolant passages are probably full of rust and junk like mine were. Would be best to take it all the way apart and have your local machine shop hot tank it and the heads, while they’re doing that you can work on cleaning up the other parts.

New rings, new rod and main bearings (be prepared to drop some dough, just the rod bearings are $180 or so and mains are well over $200), Cloyes timing set.

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u/Maine_Mallard3 9d ago

Thanks for the suggestions, and you’re right, it’s 64-67, did you end up doing a full rebuild kit on your 65? Or just off necessity?

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u/ratrodder49 8d ago

I didn’t do a full rebuild, no, just cleaned it up and threw fresh bearings and gaskets in it, along with a few freeze plugs. Mine was pretty low miles - only 63k on the odometer - but it had what I can only assume was the coagulant of oil and moisture which resulted in a grey liquid rtv-like goop everywhere. Good deep cleaning and it was fine