Cracked Flathead questions

[yngrodder]

I magnafluxed the flatty block and there are two cracks one is just started between the cyl and valve. The other must have been there for a while because someone has sleeved this cyl. has anyone ever fixed a block like this? and did you have any luck with it? Ive also read where you can machine the block between the cyl and valves to releive the valves. if the cracks are not all the way though would that fix it? and if i do that will it overheat and crack easier? How far can you bore these engines without overheating problems? I know thats a lot of questions but any help would be great. I am going to check out a couple more blocks but i dont think there any better shape. http://

[flying clutchman]

the machine shop i used to work in used to fix cracked flathead engine blocks all the time. the way my old shop fixed them is with pins.its kind of a hard process to describe. but we would pin the crack and install a sleeve in the cylinder. then they would cut out the old seat and install a new hardened seat. that pretty much took care of the crack. they can be fixed as long as they arent too big. but if you go to a machine shop ask them if they can pin the crack. hope this helps

diego

[yngrodder]

Thanks Ill see if there are any shops around me that can do that.

[Fraz]

Couple issues back Rod N Custom had an article on fixing a cracked block with some kind of threaded bolt plug thingie. Drill a hole, tap hole, insert threaded plug, tighten till it snaps off at a certain torque, continue till crack is fixed. Grind of excess plug material, all done.

[286merc]

There is nothing wrong with a sleeved cylinder, it's done all the time.
Before I would go further, get the block magnafluxed. I notice you are up in snow country so there could be freeze related problems as well as heat.

The pin process is an excellent one as long as there arent a bunch that will cost more than a good block. Cracks from bolt holes to water are common and can be ignored. Just chase the holes good and use aluminum paint on the gaskets.

[Smokin Joe]

Sleeving a cylinder is pretty common. As for size, you can open up a 239 quite a bit. I went with 3 5/16 on mine. With the Merc 4" crank that gives you 276 cubes. And you still have room to bore it to 3 3/8. In freezing country you need to check the pan rails and web around the crank for cracks too. Magnaflux is money well spent. So is the Merc crank. You get 1/4" stroke and the cost is offset by cheaper bearings than on the 59 crank.

[Nads]

The best cure for a cracked flathead is a small block chevy.

[delaware george]

i had one that had alot of water damage and needed some sleeves...for what that was gonna cost i found a real good block...might try searching for another one and keeping that one for a back up,if you have the time

[Plowboy]

I know a guy in Decatur that may have a couple decent flathead blocks. E-mail me if you are interested.

[fuel pump]

I'm told there is a place here in Michigan that welds em. They get the block real hot before welding and cools them down VERY slowly. Like two or more days. Does anybody know about that process?

[johnny bondo]

i wanna know if someones welded a crack between the valve and the cylinder and has first hand experience. my buddy can tig weld like no ones business can it be done? if its just starting to crack down the cylinder wall like an 8th inch can that be welded and ground and honed too?(piston doesnt even come up that far) just trying to save this block anyway i can.

[FrozenMerc]

Wow this is an old thread, but still very relavent.

My only experience with welding a cracked block is as such. I had a 1940 block that was cracked near the center mounting bolt of one of the water pumps. I brought the block to the local welder / blacksmith (this guy had just done a fantastic job welding my dad's cracked cast iron jointer table / fence). He told me that he would need an oven large enough to heat the block up (probably to a cherry red state), weld the crack with a high nickle content rod, and then very slowly cool the block back down. Cast iron will crack just from large temperature gradients. So welding without UNIFORM preheating and cooling will just either cause the crack to reform, or new cracks to show up in the weld area.

After all the heating and cooling, the block will still need to be decked and line bored to make sure everything is still square.

Pinning is a much better (and cheaper) method of repairing a cracked block then welding.

Good Luck

[Bruce Lancaster]

For the dedicated/crazed welders: R&C did an article on a guy who built a six-cylinder Model T by cutting up a couple af blocks and a stack of cranks and welding away.
!!!!
Anyhow, he used the preheating method and built a sort of custom furnace bt stacking fire brick around his block...contained the heat, allowed sections to be removed for welding access. I think this was heated with coal or charcoal, don't remember, but I think maybe the gas manifold things from backyard barbecues might be a modern alternative.
If you try this, please have someone film it for you tube...it'll be instructive whether you and the engine survive or not!

[rottenleonard]

the best cure for a cracked flathead is a small block chevy.

boooooooo!