I know why #3 dropped compression!


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By charliemccraney - 19 Years Ago
My engine broke a few years ago.  #3 dropped in compression and started fowling the plug in a days time.  Some of you may remember this.  Well I finally pulled the head to check things out.

There is a chunk, about 3/4 the size of a dime missing from the cylinder wall.  Forunately, It does not go through to the water jacket.  Weird.  Has anyone seen something like this?

So I guess the engine is coming out and going to the machine shop.

By PF Arcand - 19 Years Ago
At a guess, I think a Wrist Pin clip has come out of the piston. This sometimes happens if during a rebuild they aren't installed properly. Has nasty results. You may need to sleeve the cylinder to save it..  
By Ted - 19 Years Ago
Another guess would be that cylinder has a sleeve in it and a piece of the sleeve broke loose for whatever reason and is now exposing part of the original cylinder.  Delamination of the iron in the cylinder is also another guess.

Post a picture if possible or send me the picture and I'll post it for you.

By charliemccraney - 19 Years Ago
The cylinder was sleeved. #3 had some pitting that didn't come out at .060 over.

The break looks like it is in the right spot for the wrist pin to have caused the damage. I didn't notice any scores on the cylinder wall though. The cross hatch marks are still visible and all.

I'll be happy so long as the piston is still good. It is a forged flat top which seems to be hard to find now.

The motor is coming out of the truck on Sunday. I'll be tearing it down Monday. I'll have some pictures.

I'm a little weary about installing another sleeve but I had a lot of work performed on the block. Another sleeve is definitely the cheaper route.
By Hoosier Hurricane - 19 Years Ago
Charlie:

Did the engine happen to get bored .060 oversize after the sleeve was installed.  Your mention of pitting that didn't come out of the original bore at .060 made me wonder.  If the sleeve is a .093 wall sleeve, and you took .030 of that out when you bored it .060, then you only had .060 left of the sleeve wall.  At that thickness, it is possible a chunk came out as Ted mentioned.  If this is what happened, then have an 1/8" wall sleeve installed and it will be fine.

John

By charliemccraney - 19 Years Ago
John,

The cylinders were bored to .060 over before the sleeve was installed. It didn't clean up so I ok'd the sleeve rather than using a larger 312 piston. I'm not certain what the options for sleeve thickness were, however.

I haven't found many people who have seen something like this happen. I'm sure it is a fluke. I just hope the transmission or rear breaks next time. Not the bran new engine!



I haven't done anything with the heads I got from you yet. Once I get this done I'll probably start working on them.
By charliemccraney - 19 Years Ago
I got it appart today.  I posted pictures here.  http://www.y-blocksforever.com/forums/Topic1354-3-1.aspx