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1977 Cadillac Coupe DeVille
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Discussion Starter #1
So I turn on my car today and I hear this loud knocking sound under the hood, my first thought was uh-oh that's not good. So I take it to my friends dad who used to be a mechanic and he tells me it's a blown rod and I need to replace the engine. I'd like to enterntain the possibility that I just needed to change the oil and it will work but it's only a matter of time before it goes and to fix this with a temporary solution would not be very wise.

I need some opinions from you experts: what are my options here? I really need to buy a whole new engine block or will a short block do? Will I be able to mount it with my mechanic? If I drop 1800$ on a new engine what stock parts are left under the hood that could still give me problems in the future? If I replace the engine how many miles is it good for with routine maintenece?

I desperately need some opinions I can't even get to work to pay for this I'm going to have to sell everything I own. I'm only 17 and this is a big thing to deal with, please help any bit of insight is greatly appreaciated
 

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Super Moderator
2014 ELR
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10,166 Posts
Pull the engine, take the pan off, find the bad bearing and fix it. You may need to get the crank turned, or replace it. You don't need a new engine for a bad bearing. If you do it yourself, the labour is free :D

A perfect opportunity to learn about engines!
 

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1977 Cadillac Coupe DeVille
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Discussion Starter #3
what tools do I need? How do I take out the engine? And what if this isn't the problem?
 

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2014 ELR
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Lots of sockets and open end wrenches. You don't have any tools yet? Time for a trip to Sears. You really need a tool set if you are going to own an old car. We need to get you and Durrk together! lol

Start with AT LEAST something like this:


One quick check before you decide it is the engine. Take off the trans inspection cover (right behind the engine), and carefully inspect the flywheel. Make sure it isn't broken. Turn the engine over and check all the torque converter mounting bolts. Either of these can make knocking noises. They don't sound like a bad rod bearing to an experienced mechanic, however.

You can also figure out the bad bearing by just taking off the oil pan. Remove the engine mount bolts, and gently jack up the engine just enough to give clearance to get the pan out. Shove a couple of pieces of 2x4 in between the mounts and the frame to hold the engine after you remove the jack. Take off the pan (don't forget to drain the oil first!), and see which rod is loose. This will give you an idea of what you are dealing with. If you are really lucky, you could just replace the bearings on that one rod and put it back together. Not the recommended fix, though...

If this were my car, I would be swapping in a 76 500 in a heartbeat. You will have to do some looking, but why go through all the trouble to put the little 425 back in there? Find a good 500. Easiest way is to buy a whole car. This way, you know how it is going to run. Park it next to your 77. Start taking all the parts off your 77. All the accessories, etc. Leave the AC compressor connected, and just swing it out of the way. Yank out the bad 425. Get the 500 ready by doing the exact same thing. Pull that engine, clean it up, put new gaskets everywhere to ensure no leaks. Put it in your 77, and put the 77 accessories back in place. Enjoy your car. I would suggest swapping in a better cam while the 500 is out, but that requires more learning on your part.

Where are you? I'll see if I can find you an engine. You can use another 425, a 368, a 472, or a 500. All will fit, and work perfectly.
 

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95 FWB 81SDV 96 FWB 94 Fleetwood
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Get another junk yard motor and put it in... any 472, 500 or 425 will bolt right in.. thats a motor from 1968 to 1979..... even a 1980-81 will fit , but they are way to underpowered for your car...
 

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1977 Cadillac Coupe DeVille
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Discussion Starter #6
I live in southeast connecticut 1 hour from NYC. I've got plenty of tools that I'll be able to use for this so I'm hoping to have an accurate diagnosis of what this is before the end of the weekend. As for the replacement block I'll take whatever works but I am looking to keep it under 2 grand. Since I'm not going to pay someone to put it in I might have to get that 500 :).

I've found a few websites selling rebuilt 425's and such, what is your opinion on buying it online? I figure they can't sell me a dud engine but am I better off taking it out of another car so I can hear and see it run first?
 

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I've found a few websites selling rebuilt 425's and such, what is your opinion on buying it online? I figure they can't sell me a dud engine but am I better off taking it out of another car so I can hear and see it run first?
You will spend more on a rebuilt than the car is worth. Get a used motor, and like I said, get it from another car (or buy the whole car) so you can check it running. You can buy from a junkyard, and they will give you a warranty, but who wants to swap things twice?
 

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1977 Cadillac Coupe DeVille
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Discussion Starter #8
just put in an online request for a new engine from all junk yards in CT and within 5 minutes I had someone offer me a 425 block for 1500 shipped. He said that there were 2 types of 425's though, an EFI and something else he had a really bad accent. Is the engine type something I should worry about or does it not matter?
 

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Take your time! You will find engines cheaper than that. You will find running cars for less than that, too! Be patient!

Yes, there was a carb and EFI option. What's yours? Not that it really matters. Just use your intake on whatever you get (if it is a 425).
 

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1977 Cadillac Coupe DeVille
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Discussion Starter #10
I'm not sure what type my engine is, would I be able to find out just by looking at it?

What kind of car should I look for that would have a 425 engine that I can swap?
 

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1990 Brougham
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I live in southeast connecticut 1 hour from NYC. I've got plenty of tools that I'll be able to use for this so I'm hoping to have an accurate diagnosis of what this is before the end of the weekend. As for the replacement block I'll take whatever works but I am looking to keep it under 2 grand. Since I'm not going to pay someone to put it in I might have to get that 500 :).

I've found a few websites selling rebuilt 425's and such, what is your opinion on buying it online? I figure they can't sell me a dud engine but am I better off taking it out of another car so I can hear and see it run first?
not to thread-jack this or anything, but where in south east connecticut? im in the ledyard/gales ferry area and id be happy to lend a hand! im 18 and i have a few good tools i could let you use.
 

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77 CDV, 06 DTS III, 69 FWB
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If your car is fuel injected, it will have the motor code "T" in the VIN. Carburated is motor code "S". The original air cleaner cover would say "Electronic Fuel Injection" on it, there would be a "Fuel Injection" badge on the instrument panel just above the steering column, and one on the trunk under the "Cadillac" script emblem on the passenger side. It was a very rare option for the Devilles and Fleetwoods, so more than likely you have the carburated engine.

The 425 motor was standard on all Devilles and Fleetwoods from 1977-1979, and 1977-1978 Eldorados.

Sorry to hear about your troubles. Good luck!

Craig
 

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Here you go:

1976 Coupe Deville with 72 000 miles, with a 500

Buy it Now for 2500. Pull the engine, and make lots of money parting out the rest of the car before you make a couple hundred in scrap when you send it to the crusher. This is what I'm talking about...

Here is a 73 limo with a 472 for 1200

These are the kind of deals you need to be looking for. You will find cheaper stuff locally. Look on craigslist, etc. It costs money to sell on ebay, so prices are higher.
 

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1977 Cadillac Coupe DeVille
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Discussion Starter #14
wow nice finds thanks jay, that first one looks good I easily could make most of my money back too and have the new engine. The only problem is how I get it from las vegas to here. Ill work on that.

When I search for these cars on craigslist/ eBay what should i look for to decide that the engine is worthy of swapping in? Less miles or what?
 

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Not so much the miles, but the maintenance. See how it has been taken care of. Regular oil changes, etc. Even if they don't have receipts, check the inside of the driver's door for oil change stickers. For example, I just bought another car. The owner had all the maintenance records back to when the car was new (1994). I can see that everything has been taken care of, and don't have to worry about replacing things that have already been done. Of course, since all you want is the engine, you don't need lots of info on the rest of the car...
 

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1977 Cadillac Coupe DeVille
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Discussion Starter #18
hmm very tempting offer jay I might have to take you up on that haha.

As of right now the car got towed to Midas to this guy I know who is going to properly diagnose the engine problem and tell me what my options are. The future of the car will be annouced later today.
 

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1977 Cadillac Coupe DeVille
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Discussion Starter #20
yep that's defanitly it. So I've got my eyes peeled for some good prices on cars/engines so I can get this sorted out soon. If anybody finds some good options please post them, and I'll post some I find to get some opinions
 
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