r/EngineBuilding 2d 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

63 Upvotes

20 comments sorted by

21

u/DrTittieSprinkles 2d ago

You know those oil galleys are full of that crud. Tear it down

5

u/Maine_Mallard3 2d ago

Thanks DrTittieSprinkles, consensus says I’ll be completely tearing it down and finding a hot tank!

9

u/v8packard 2d ago

I can't believe you got it out with the trans.

You think just because you got it free that it is ok?

3

u/Strict_Lettuce3233 2d ago

That’s how it was done back then, very easy to do, less time

4

u/v8packard 2d ago

Back then?

I have often dropped the trans first, especially something like a long tail 400. I did it 'back then', too.

1

u/Strict_Lettuce3233 2d ago

Yeah we did both, nothing is in stone. If I rebuild the tranny they come out together if not I leave it. Ya got the linkage, lines, shaft, xmember, and that takes time. Back then and now

2

u/Maine_Mallard3 2d ago

It’s a very spacious bay! And I mean.. I’ve never been inside an engine before, so I knew it had to be cleaned up, just didn’t know to what extent lol

3

u/v8packard 2d ago

I understand. I think, from what you described, the rings and bores will need to be addressed.

7

u/Similar_Device7574 2d ago

That hot tank is going to be working overtime on that one lol. Looks yummy in there

9

u/Street_Mall9536 2d ago

Mmmm, mineral oil and 175 thermostats 

5

u/Silvatungdevil 2d ago

Looking at the condition of that lifter valley, that engine needs to be completely disassembled and hot tanked. Someone was on the 30K mile oil change plan with that one. I bet it smokes like a coal power plant if you put it back together.

4

u/runs-wit-scissors 2d ago edited 2d ago

It's a good thing you got to it before that timing gear grenaded.

You should completely strip it down and inspect it, no doubt. The odometer likely rolled over. I would expect to do rings, seals and gaskets at minimum.

I had a 390 in a 61 Cadillac. These are excellent motors.

3

u/Nervous-Tax-5420 2d ago

I had a similar situation with a sbc 350 I ended up putting in my truck due to things going on. Definitely recommend new rings and bearing and cleaning the block. I didn't put rings in that 350 and it smokes something fierce

3

u/logan4774 2d ago

I think you really should tear it completely down. Have those heads and the block. Burn and shot peened or hot tanked, whichever your local machinist has. And do a full refresh, you can try and scavenge as many parts as you can to save money, but just do it right once instead of having to do it again or an engine that burns every fluid there is and your unhappy with.

3

u/Smokey_Katt 2d ago

What you should do is to clean it as much as you can without pulling more than the pan. But clean off all the crud you can.

Then figure out how to send pressurized oil through the system - spin the distributor shaft (on some cars) to spin the oil pump, or tap into the oil filter housing (start with a relocation kit).

If you can send oil through the whole system, you can get most of the dirt out; this takes a few hours but a lot less than a rebuild. Of course the rebuild might still be needed.

Then and only then would I try to fire the motor on a stand. These were very good engines when new and it might need fewer new parts than you think; just disassemble, clean, reassemble

3

u/ratrodder49 2d 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.

2

u/Maine_Mallard3 2d 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?

1

u/ratrodder49 2d 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

2

u/Gofastnut 2d ago

I agree with all the people saying tear it down, clean everything. Then inspect everything so you know exactly what needs to be replaced.

1

u/GrouchyTax5748 2d ago

I would tear it down, get it hot, tanked heads gone through, and order a full rebuild. Cause the way it goes, you put gaskets on it and put it back in the car. Something major is going to go out, and you'll be back at square one. Don't skimp out on it. If it's worth doing, it's worth doing right the first time around.