I have a 79' Cat 931B with a blown motor. Like holes in the block, chunks of camshaft in the pan blown... The rest of the machine is in good shape with lots of life on the undercarriage, so I'd like to fix her instead of parting out. Located in Boulder, CO. I have all of a few hundred hours on machine, and while I am pretty handy with vehicles and engines - I am not a heavy equipment guy. I assume I am looking at a rebuilt or used engine and swapping. Would be happy to rebuild it, but I am getting out of my depth as far as what my options are. Thoughts from the collective mind? Thx
The problem youll have is finding a good block. I just did one over for a machine of ours and had about 6000 in machine work and parts. You may wind up having to buy a whole machine to get a engine. A d3 engine will bolt right up. It soumds like yours probably had a wrist pin fail. Pretty common thing to happen to a 3204
Doesn't sound like yours is worth trying to rebuild if it has holes in the block. Some pics. would help though. If the holes are not in a critical area they could maybe be repaired.
What Welder Dave suggests, but here is a suggestion that is really off the wall: Also depends on where you are coming at the issue from. Since that loader is 45 years old, I'd be guessing that it is on a farm or somewhere where you don't much need to make a buck with it. For example, pretty much all my iron is in the same boat as you: I run a 51 year old Case 580B every day on my "stump ranch" feeding horses, getting firewood, clearing snow, and just about anything else you can do with a rubber tired tractor/loader/backhoe. My newest farm tractor is 1963. My d6 is 1973, D4D is 1969, etc.etc. Making do without using new OEM parts is the norm around here. I'm doing a little guessing here, but isn't your machine drive from the engine to the transmission pretty much like most of the other small Caterpillar drives: A short drive shaft from the engine, which pretty well divorces the engine from whatever transmission is behind it? So an option might be to find a suitable donor engine from something wildly different, such as a Ford 7.4 V8 diesel or the like. I'm not sure I would suggest a gasoline engine but some sort of diesel that this more popular and 'way less costly to acquire (than Cat engines) might be worth looking at. Something where parts are a little more common and not as pricey. I suggested a V8 diesel because I'm not that familiar with any other diesel pickup engines--I'm sure there are lots of candidate engines out there. It seems to me that the Cat engine mountings are basically 3 points: 1 point up front and 2 points back by the flywheel. So the connection to the transmission is either a short shaft with some rubber shear couplings which is the stock setup. Just use 2 U-joints which will not require careful alignment of the transmission to the engine. The only significant challenge is to pick up a hydraulic pump drive location off the donor engine. The easiest location is off the front of the engine but that location depends on the clearances available. YMMV!! Let us know how you are going about fixing it! Jon.
Not my area of expertise, but what about a cummins 4bt?
It's only a 65 HP engine. Too much HP could tear the drivetrain up. You could look on Machinery Trader for dismantled machines for a suitable block for rebuilding. A few years ago there was a complete 931B for sale I think with a backhoe for a reasonable price because the transmission had issues. Cat 910 loaders also used a 3204. D3, D3B, D3C, 931, 931B, 931C are candidates as well as some D4's and I think smaller IT model loaders. I'm not sure if the turbo models use the same basic components but maybe could use a block from one and some components like the injection pump off your existing engine.
One of my questions is how specific is the 3204 block? If I locate a used engine or block, curious how to tell if it would work for me. My engine is a 45V. I also own a 931C with a 4-in-1 bucket, not sure how much crossover there is - keep it for parts? This is definitely casual use around the property, not making money with it. Im already about to put new undercarriage on my 931C. In a different life I would be all about putting a different engine on it, but don't have the energy or time in life right now to focus on it. Just gonna keep an eye out for a used engine I suppose. Cursory search shows me ~6k for a used pull, ~10k for a rebuilt. Ouchhhhhh. If anyone has a line on a source for en engine, I'd be grateful! -Justin
Theres feom i know 2 differnet blocks the easiest way to tell is by the oil cooler mou ting/filter area.
The first one is what yours should be the second is the later style.
I don't think there's much difference from a 931B engine to a 931C. A couple HP if I recall. The turbo models used a larger oil cooler. Not sure if you could just install a larger cooler and still use the block.
Onve you got to the c models they had the bigger oil cooler but those the injection pump is bolted to it too. To put (what im assuming to be what he has together) has need the older block. If he found a complete newer engine it should bolt right up
Blocks alone around here go for 5 grand for a bare block