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Engine Rebuild Disaster - Cylinder Crack

Csarneson

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I've been giddy to start working on my BN4 engine. I just got the block back from the machinist last weekend. It had been bored 0.030" and had cam bearings installed. Today I was excited to gap the piston rings and test fit the crank. I pulled off the bag for the first time (I mounted the block with the bag on by just tearing a hole in the side) and DISASTER. I see a giant crack down the side of cylinder 1. I trust my machinist completely so I can only assume that the crack occurred on the drive home or while I was mounting the block on the stand. I can't think of any mechanism for this at all.

Is the block toast? I don't know anything about sleeving a cylinder but can that be done in this case? My new pistons are sized for 0.030 over and are already fitted to the rods and ready. What are my options? There aren't a lot of BN4 blocks to be found in Wyoming in fact I might have the only one. I could really use some good news right now...

IMG_0699.jpgIMG_0698.jpg
Chris
 

Patrick67BJ8

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I've been giddy to start working on my BN4 engine. I just got the block back from the machinist last weekend. It had been bored 0.030" and had cam bearings installed. Today I was excited to gap the piston rings and test fit the crank. I pulled off the bag for the first time (I mounted the block with the bag on by just tearing a hole in the side) and DISASTER. I see a giant crack down the side of cylinder 1. I trust my machinist completely so I can only assume that the crack occurred on the drive home or while I was mounting the block on the stand. I can't think of any mechanism for this at all.

Is the block toast? I don't know anything about sleeving a cylinder but can that be done in this case? My new pistons are sized for 0.030 over and are already fitted to the rods and ready. What are my options? There aren't a lot of BN4 blocks to be found in Wyoming in fact I might have the only one. I could really use some good news right now...

View attachment 47289View attachment 47290
Chris
I had an engine with one bad cylinder sleeved on the bad cylinder.
 

Healey Nut

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Was the block overbored by your machinist and by how much . When you picked it up and took it home did it go through a huge temperature change from where it was to your garage ?
 
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Csarneson

Csarneson

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The cylinders were bored 30 thousandths. That's usually pretty minimal. There shouldn't have been much temperature change from the machine shop to my shop. The entire thing is a mystery to me.

It sounds as though sleeving it is a possibility. Moss doesn't sell BN4 sleeves but AH Spares in England does for around $30. Sounds like I'm going to be placing an order and crossing my fingers.

At a minimum you guys have talked me off the ledge and gotten me to put the Bourbon down. That's a big step. You guys are a lifesaver.
 

TFR1

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I have purchased sleeves from LA Sleeve. Just do a search.
They made custom sleeves for me at very reasonable prices.
 
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Strange to me that the crack is in the middle of the cylinder; if it's from some sort of stress I'd expect it to start at either end. Sure it's not a scratch?
 

Patrick67BJ8

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Strange to me that the crack is in the middle of the cylinder; if it's from some sort of stress I'd expect it to start at either end. Sure it's not a scratch?
Maybe best to start with the Machinest and have him confirm a crack or scratch. No sense in wasting good bourbon!
 

Healey Nut

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Strange to me that the crack is in the middle of the cylinder; if it's from some sort of stress I'd expect it to start at either end. Sure it's not a scratch?

Never seen scratches with such an irregular pattern . Thats a crack .
 

Jim 58 BN6

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A dumb question, and I sure don't want to add to the OP's stress level (or Bourbon intake), but does a crack like that need to be drilled or somehow ground or treated at the ends before the sleeve is installed? I know a lot of blocks have been saved by installing sleeves, but I'm just wondering if anything else should be done to stop the crack from possibly enlarging.

Maybe it's a non-issue, but I thought I would ask. Good luck, I think that the right machinist can probably save it. Jim
 

RAC68

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First, although I am no expert on this subject, I have known others who have used cylinder liners to fix such issues with good results. However, I also agree with Patrick and would first talk to your machinist to have him verify the issue and get his recommendations before going further.

Keep in mind, you are actually in the process of building your repertoire of Healey stories. Then, when conversing with other enthusiasts at a local pub or outing where they are telling their stories of overcoming Healey adversity, you can respond with:

"If you think that's bad, let me tell you what happened to me!"

All the Best,
Ray(64BJ8P1)
 
Last edited:

blueskies

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It usually takes quite a bit to crack a block, which makes me wonder whether the crack was there before they bored it out, or whether it happened while in their care. Unless you have a lot of confidence in that machine shop, you may want to look for another shop. Either way, have them thoroughly check your block. They also likely can source a liner if the block is repairable.
 

Healey 100

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If you sleeve it, I suggest sleeving all the cylinders to the original bore. I did that to my 100 and it worked out well with no problems. I suspect the vendor who sold you the .030 pistons will trade them for nominal bore pistons. I had this done years ago by a local engine machine shop and it was not very expensive.
 

Keoke

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All the previous suggestions are great
However ,you might consider locating a clean used block.
 

steveg

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If you sleeve it, I suggest sleeving all the cylinders to the original bore. I did that to my 100 and it worked out well with no problems. I suspect the vendor who sold you the .030 pistons will trade them for nominal bore pistons. I had this done years ago by a local engine machine shop and it was not very expensive.

The Los Angeles-area mechanic, Russ Thompson, has had one sleeve in his .060"-overbored tricarb BN7 for years with no problems. Not sure why it would be helpful to go to all the work of sleeving all cylinders and swapping back to non-overbore pistons. Just saying.
 
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Csarneson

Csarneson

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I took it to my machinist this morning and he says that sleeving it is no big deal. He apologized for not seeing it when he cleaned up the block after boring. He suspected that rust must have done some work inside the water jacket on the backside and weakened it. The block sat disassembled for 40 years in a barn so that's certainly a possibility. He's going to sleeve it and take it back out to the 0.030 over size. He tells me that for just $150-ish it should be better than it was. He's also pledged to carefully check the rest of the block for any other problems. I suppose if the cylinder wall was weak then it's probably good that we caught it now and not after it's back together and running.

Thanks for the guidance and support guys. This is all new stuff to me.

Only a moderate amount of bourbon was sacrificed for this story. I'm still pretty wound up over the issue so there might need to be a little bit more until I have it back and repaired.

Chris
 

RAC68

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Hi Chris,

Great news.

You will find that Healey ownership will provide many opportunities to overcome presented issues and the chance to create and add your own something different. Both provide a euphoric feeling of achievement and a story to relate to fellow enthusiasts (who can appreciate what you have done), especially at the Pub.

Take it slow and preserve your energy as there will be other challenges to enjoy.

All the best,
Ray(64BJ8P1)
 

CLEAH

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Only a moderate amount of bourbon was sacrificed for this story.

Chris

Chris, unless you sloshed the bourbon out of your glass because you were shaking so much, no bourbon consumed is bourbon sacrificed!
 
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Csarneson

Csarneson

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Chris, unless you sloshed the bourbon out of your glass because you were shaking so much, no bourbon consumed is bourbon sacrificed!

I was pretty stressed and upset. I'm not sure that I was able to really enjoy it. Thus the sacrifice comment.
 
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