Fair price for a 70 Diesel

Talking with a guy at work, on his farm is a 70 diesel his sister in law owns. It came up in conversation when I said I'd like one some day. It's original. Runs and drives, but the big but is the pony motor block is cracked. He says it still runs, he just doesn't use it because they bypassed the coolant. He thinks I could get the tractor for a $1000 which I think could be a steal, but what am I in for with the pony motor. He thinks it maybe repairable as he thinks it may be only cracked outside since it still ran and no water was in the oil. This is very early stages of thinking about buying and I have not seen it.

Neighbour had a thrashed Pony motor on his JD 70 D.......he installed an electric starter.......Perfect alternative....
Bob......

I like the idea of having a pony motor, but am I looking at a money pit to repair or replace?

The pony motor is as expensive or maybe worse than the big engine , I would either use a chain or make it electric start or sell it .

Had a neighbor with 720D that had a cracked block pop motor. He had it for about ten years when he found out the previous owner had blocked the cooling line to the pop motor. He was in the habit of starting the big motor real quick and shutting the pop motor rightaway. Used it that way till he quit farming, actually he passed away a few year later. In my opinion if it runs and big engine start quickly, use it till it's dead.

OK, you are telling what I expected to hear. What about a going price for one in this shape. Tin is suppose to be all there and pretty straight. Rest of the tractor is suppose to functional and he could easily get it started for me to hear run. Like I said, early stages of consideration, maybe next spring at the earliest I'd actually get serious.

I have owned a 730D since 1975 electric start and have spent at lease $1500 on batteries in that time. they last 3 to 4 years and I have learned to change them all out at the same time. This last year I changed to 12 volt batteries because of price. I could buy two of the biggest 12Vs that I could fit into the battery box cheaper then I could buy four of the small 6 volts for. A best friend has a nice 720D pony start and when he needs a new battery he just buys one 6 volt and he's good to go. And the 730 was never my main tractor. So my thought is if you're going to have to over haul the pony and you are going to keep the tractor for some time its a wash. Plus you can start it in cold weather any time you want. just my thought.

If I buy it, I would see myself keeping it a long time. It would be pretty much a toy.

$1,000 is a steal for this, you should be arrested it's such a steal.

As suggested earlier, start your waterless pony equipped 70D that you stole at that price very quickly and never give it another thought. If you need this in the winter time, install a tank heater to get the big engine warm and start it quickly.

This is the going price for a common A in decent running shape. 70D should be a good deal higher, but I have no idea how much extra is the fair market value.

How much it will cost to fix the crack depends on how good you are at brazing cast iron, you have a year to practice. And of course the extent and location of the crack itself. You may need to pull the pony in order to get at it for a good repair. Cast iron is very easy to braze and if you drill holes at the ends of the crack, and v groove the crack itself to accept the bronze, there is a very good chance you can fix this yourself and never have another issue with the water jacket.

You'll see a lot of fiberglass blankets used to retain heat if you search youtube for cast iron brazing - never did that in my day and never needed to. I've never had cast iron crack further from a brazing job ever.

Pricing for overhaul is unfortunately the truth - higher or as high as the big engine and they too are pricey on this model. So - don't overhaul it?

If you plan to keep it a long time the purchase price is less of a consideration. Where you spend money on reviving 70 diesels that have been worked hard an parked for a few years is in the rear rims and tires (~$1000), clutch pack rebuild parts ($250), water pump rebuild ($100), grill screens ($80), front tires ($200), seat cushions ($100), battery box ($150), head lights ($100) etc, etc. This assumes there's no major mechanical issues (loose flywheel, bad transmission 3/4 gear, weak injectors, loose cam idler gear, etc.). These are all common problems with 70 diesels. You can buy a used pony engine for ~$900 if you cannot repair the crack in the current engine. Pull the flywheel cover off before you buy and check to see if everything is original and ok. I've seen some 70D flywheels welded to the crankshaft. I bought a 70D like you described for $500 and had $3500 into it before it was usable and reliable.