I was on the happy road to building a motor featured in a 1996 Hotrod Magazine article named, "The Smallblock Chevy Should Have Built". This is a motor based on a 400 block. Through a miscommunication with the seller of the block I used, the block was not magged. I payed the price for that mistake. The block developed a hairline crack in the 8 hole (no pun jokes, please)during break-in. A good friend that was with me during tear-down suggested having it sleeved. At first I was appalled at the suggestion because of all the publications I've read stating how it's a bad idea. As I researched it further, I was surprised how many medium performance motor owners have needed to go this route. Now I feel like I may have been a little hasty in dismissing the notion. I have about $600 worth of quality machine work in the block. I would hate to throw that money away. I'm quite certain that during break-in, the motor showed signs of being in the 400 to 415 horsepower range and will remain that way for it's life. At this power level, would you sleeve?

 

I don't see where sleeving would be a problem. The cylinder is bored out and the sleeve is put in. My buddie and his Dad have done this many times in their machine shop. I'm sure someone can answer in more specifics but I will ask him when I get to work this afternoon and see what he thinks. I'm guessing he will say it's fine. If your going to throw it away, send it to me, I will take it for free and pay for shipping.

 

Forget how much money you've got in this block. That's water under the bridge.

The "real" consideration is how much money it will take to get it back together. If finding another block and getting it up to snuff costs less than what it would take to sleeve this block, this block is history. However, if sleeving this block will be all that's required to get it up to snuff, and that's less than getting another block up to snuff, then this block is saved.

 

Make sense, five7. It will cost me $25 to have the block magged to insure no other "surprises" and if there are none, sleeving is $125 and another $20 to torque plate hone the one hole.

 

I think it's worth sleeving. 400 blocks are getting real hard to come by these days. Those aren't bad prices for what they want to do either.

 

Yeah, the machinist, besides being very skilled, is sympathetic...and I bring him lots of business.

 

I've had a couple of sleeves done in blocks I've damaged. It's cheaper to have a sleeve or 2 installed than finding another block then get all the machining done to it.

I finally broke that block beyond repair and have a different one in the car. I now have 2 spare 454 blocks and still have an old 400 block in my garage.

A 400 block because they're getting hard to find could have all 8 holes sleeved back to original specs if it's been bored out to max. Before getting all 8 done though I'd price out a new aftermarket 400 block first. The cost to get 8 sleeves might be more than a new aftermarket block. One or two sleeves isn't going to break the bank.

 

Sleeving a block to repair a cracked cylinder is a good repair if done right.

Some machine shops bore the block to the exact size of the sleeve and "glue" the sleeve in.

A better but more complicated method is to bore the cylinder
.001" under size and freeze/chill the sleeve before installing it.
( the last one we did we threw the sleeve out in the snow for few hours) Then quickly tap the cold sleeve into the still warm freshly bored cylinder.
When the block cools and the sleeve warms up to room temp, this creats a permenant press fit seal that doesn't leak. (no sealer is required) Many machinist don't like to bother with this method cause it takes longer, requires presision boreing and sometimes the sleeve splits if not done right.

When done right the new sleeved cylinder is actually thicker and stronger than the origional cylinder.
All aluminum blocks are sleeved.

 

"Done wrong" would include one instance I saw where the cylinder was bored for the sleeve all the way through, instead of cutting in a "step" for the sleeve to bottom out on. Over time the sleeve migrated downward until the top of the sleeve was below the top ring. The results weren't pretty.

 

Thanks for the replies. They have been very helpful.

 

Sleeve a cracked block? Not so sure I'd go that route unless I was sure the crack was repaired and would not continue.

When the sleeve is inserted, it'll put pressure on the block, if the crack is still there, it'd stand to reason the crack would get larger.

Just my .02

 

He's going to have the block magafluxed and hopefully that will reveal any surprises. Good point though.