Dear Ole Mechanic;

OK, I messed up my old Ford tractor big time.  I forgot that last summer when the water pump went out and got replaced, all I put back in it was water.  That cold snap we had froze the water, and the engine block now has a crack along the lower left side of it.  The tractor is a 1951 8N that I use for shredding weeds and blading the driveway.  Is there some way that the crack can be repaired?  If not, then are there any other options for saving the tractor?Cracked Block

Busted Block
 

Dear Busted;

Yep, when they freeze, that's usually where they crack.  Can it be repaired?  Maybe, but maybe is also the first part of maybe not.  The first thing to do is to determine if the engine block is cracked on the inside too.  Did any water get into the oil pan?  The oil pan should be pulled off so that the inside of the block can be checked, too.  To get the oil pan off, the front axle must be removed.  That is because the oil pan is part of the frame, and the axle mounts are bolted to the pan.  To remove the front axle, the engine must be supported from the top with a chain fall or other support that will allow the pan to be pulled out the bottom.  It needs to be a sturdy support, as someone will be under the tractor checking the inside of the blocks for cracks. 

There are a couple of different ways to try to repair cracks in a cast iron block.  The first is welding, and the second is what I call plug and stitch.  There are drawbacks to both methods of repair.

The drawback to welding is that the rate of expansion and contraction of cast iron is different than the rate of expansion and contraction of the weld material.  The result is that after welding, the cast iron contracts away from the weld material as it cools, and that tends to crack the cast iron away from the weld.  Ya still got a crack.  To keep the cast iron from getting too hot and expanding more then contracting, you should weld only about one inch at a time and then allow things to cool back to room temperature before welding the next inch.  The recommended rod for stick welding would be a high nickel-content rod or a special cast-iron rod.  Other people have had success with regular wire-feed welding--again, only one inch at a time.

The plug and stitch repair involves starting at one end of the crack, drilling a hole, tapping the hole with threads, and screwing in a cast iron plug.  Then, cut and grind the plug back flush with the block.  The next hole along the crack should overlap the first plug by about one forth to one third of its width; then, repeat the tap, cast iron plug, and cut and grind operation. The third plug should overlap the second one, and so on until you reach the other end of the crack.  One problem with this method would be if the cast iron block is too thin to get enough threads in it.

So, there can be problems with either of the repairs that I've suggested.  There is one other way to correct your cracked block.  That would be a replacement engine.  Any Ford N series engine from 1939 thru 1952 is a direct replacement for your engine.  Also, rebuilt engines are available from a number of places like Tractor Supply Co®  or Valu-Bilt®, but they start at about $2,500 and go up in price from there.  There are also adapter kits to put newer engines in the N-Series tractors, but they get very involved and even more expensive than rebuilt engines.

You may have noticed that I have not mentioned any of the stop-leak products.  That is because I consider them to be no more than a Band Aid®, as they are only a temporary patch and not a repair.

Bet you don’t forget the antifreeze next time!

Herr Professor Nuzanbolts