Thread: crack in flathead engine

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My good friend and I are putting together a 46 ford coupe with a 51 merc flathead engine. The engine was picked up and magnaflux and found to have a crack of about 1/16" running along number 2 cylinder wall. My question can we weld it ourselves(were both fairly good welders) and hone it out afterwards or should we sleeve it. I love working on flathead engines but neither of us has done this before. Would we still get water pass the waterjackets if we sleeved it, and would we have to bore the remaining cylinderswhich are Ok but the difference in cylinders thickness between #2 and the rest would be different would they not?

I wouldn't reccomend it. There are shops which specialize in the repair of blocks, but it might even be cheaper to find another block.

My supervisor tried welding the block on his tractor, and each weld created a new crack further up as it cooled.

If you are REALLY good welder, and have the capability to preheat the block, anneal it after weld, and cool it SLOWLY, then you might have a chance. Otherwise, send it out.

I second the advice of firebird77clone. The only way to "maybe" get a good weld on cast iron is to heat the block in an oven and weld it hot and then anneal it and slowly cool it. One other very chancy method is to sleeve it and braze the top edge to seal it and then bore out the sleeve to the size of the other cylinders. Do you mean a 1/16 wide crack all the way down in the bore? If so that is probably not repairable. The chance of you patching this yourself is less than 1% in my opinion. I recall trying this on a Model-A block, getting a nice weld and then when it cooled it went tinkle, tinkle and cracked worse than before because I had no way to anneal the weld. Even with professional help and an experienced shop with annealing facilities I would still say the chance of a successful patch is only about 50%. Take it to a shop which has experience in such repair and cross your fingers and maybe you will get lucky?

Don Shillady
Retired Scientist.teen rodder

Thanks for your answers. I thought that a crack that was 1/16" long that ran just about the whole side the the wall would be just about impossible to weld. Might just give it a try to increase my welding possibilities.

Is there a reason for the risk? Welding the block sounds "iffy", especially in light of the lack of preheating and anealing. If you did get it welded and built an engine around this block, what are you risking in the event that it didnt work? I would hate to see someone put a bunch of $$ and time in a neat flat motor and have it fall down because of the patch...... if you are building it with used, stock stuff, then the risk is much less and might warrant the roll of the dice..... good luck on whatever you decide.

Robot We are already in the process of getting a another flattie out of a 50 ford which is running now. The 51 if we can fix we will, but if not just alot of experience. We will keep all the parts.

Have you seen the new flathead blocks (not the French ones)?

http://www.motorcityspeedequipment.c...ge_id=newblock

Should be neat if thay are affordable!!!

mike in tucson

Yep I read that article a few month ago and I'm waiting to see what they cost. They have so much improvement over the origional it amazing. I would love to buy one and put it in my 37. Not many chevy's running with a flattie.

Well the best thing about the '51 Merc is the crankshaft and the rods that go with it. Have that cleaned up and make sure you use the right pistons for the longer throw and you will have one very torquey flathead. I guess you know not to overbore too much because of the possibility of core shifts and thin spots which lead to overheating or worse. If the block is the standard bore of 3 3/16" and only needs a cleanup by 0.030", do that and don't tempt fate by going to 3 5/16"; the added stroke will really give the torque a boost and maybe you won't have to worry so much about overheating. I envy your project, you can end up with a nice closed car for year round driving and still enjoy the fat-fender era. I had a '47 Ford convertible in High school and dechromed it, painted it Aztec Red with wide whitewalls and had a mildly rebuilt flathead. It was fantastic for cruising but beware the standard translmission is fragile. Sadly I sold mine when I broke the tranmission for the third time but I should have kept it and saved it until I could get a stronger trans like a packard floor shift, but then of course the SBC era began and flatheads went into decline. Well have fun!

Don Shillady
Retired Scientist/teen rodder

Don Know what you mean about the trannys. I had a 41 ford pickup with a 53 merc engine that was wild. It put out probably 180-190HP in a truck that had the bed cut 12" and was channeled 3". Not much weight and she was a mover. Went through 2 tranny and at least the same rears. One night after haviing a few to many beers, I raced a kid that had a 53 chevy with a 265 running 2-4's. I knew I could take him and since I was running open drive shaft for pipes along the side of my cab, it was loud. Well burned about 200' of rubber in first gear and went to shift into second,Bang. Rear end went. Managed to creep home about 10 MPH and parked it. Had alot of fun with that. Wish I never sold it.