The Stovebolt Site Forums The Shop Area Engine Shop A Serious Question About My Engine Rebuild.

So I have had my 248 in the shop for almost two months now. When it got to the machine shop the owner said he Magnafluxed it and there was no cracks. Everything looked good. He ordered new parts. The last time I was there he had it on the boring machine. There was a delay because they sent the wrong valves. After not hearing from him for three weeks I call and he tells me they found a crack in one of the cylinders and the had to weld it. I don't know allot, but it seems to me that would mean that they would have to re bore it. Wouldn't that mean they need to put a bigger piston in? What should I ask him tomorrow? I was a little [censored] today so I let it go, but I have some serious concerns that they cracked it. Is that possible? Tell me what to do!!!

I haven't heard of welding a cracked cylinder but I would want a sleeve in there myself. A buddy of mine was having his 216 rebuilt and when they were boring, they ran into rust holes from the water jacket. They installed sleeves.

I have been at this a long time and I have never heard of welding a cylinder. Sounds like a BIG NO-NO
It is common to sleeve a cracked cylinder.
I would take your engine to a different shop if possible.

If you bore one cylinder don't you have to bore all the cylinders.
I don't think you can have different size pistons in one engine.
The pistons all have to be the same size, Right?

jorb

During the Great Depression they may have bored one cylinder only, but not since then.

He already bored all the cylinders, then he found the crack. I would think he will need to re bore all of them to match. I'll go over and sort things out today.

You need to see where the crack is before getting worked up, if its at the top of the bore on the deck, then welding would be OK, deep in the bore is really wrong and a sleeve should be used. Boring one bigger would not kill the engine, its not ideal and will work, but a sleeve and boring to the original size would be better. Don't bore all bigger just to match one, sleeve one back down. In the future if something was to happen or it needed bored again, you will be out of material to cut and six sleeves will be needed.

Time to go see for yourself and push to get it done or moved, two months is way to long.

Sleeves come from the factory slightly under standard cylinder size, and they can be bored to whatever size the rest of the cylinders are. Sleeves come in either 3/32" or 1/8" wall thickness. Here's the drill:

Bore the damaged hole either 3/16" or 1/4" oversize, depending on the sleeve wall thickness. Leave the hole about .002" smaller than the sleeve diameter.

Drive the sleeve into the hole, using a piece of steel plate and a BFH. Face the sleeve off flush with the top of the block.

Bore the sleeve inside diameter to match the other cylinders.

If a crack or hole is within 1/2" of the top or bottom of the cylinder, junk the block.
Jerry

When sleeving valves putting it in dry ice greatly reduces the installation force requirement and is there a reason not to do that for automotive applications? IMO there's no way a weld repair will match the hardness of the parent material so if there's any possibility a piston ring could make contact with the weld it will wear out rapidly.

248s are pretty common, I'd be looking for a new block.

Crisis not a crisis.

It was my mistake and misunderstanding. He needed to cold weld the combustion chamber in the head!! Not the block. He said it was a very minimal crack that was considered within the normal/common range.

He's said my motor is coming along beautifully!!!

Lesson learned. Listen better!!

Well, that's good then. I'll bet you let out a sigh of relief!

What sort of valves are you referring to? I shrink valve seat inserts in cylinder heads in a dry ice/alcohol mix before installation, but the shrink fit is much tighter than a cylinder sleeve. A cylinder sleeve is also several inches long, and the hammer method helps it align properly with the bored hole as it's driven in. I've also used a hydraulic press to push the sleeves into place, but the hammer method seems to work the best.
Jerry

Doh! My post makes little sense if one doesn’t know I’m referring to a valve like this with shaft bores similar to that of automotive cylinders. Possibly cast iron sleeves are more cooperative to work with than always having to match the parent material.

"cold weld the combustion chamber"

What is cold weld? Is that like hot ice?