John Deere 2 cyl engine bore limits

Hey guys I don't know if this has been discussed before. The other night I was having trouble sleeping, so I decided to price some over bore kits for my 44 model A. I stumbled across some 6 in power block pistons on ebay. Now I am not purchasing pistons anytime soon , but I was wondering how far can a stock block be bored out without hitting a water jacket, or cooling passage whatever you want to call it. Obviously I know you can get .125 overbore kits
 
We're making blocks that will go 7. The don't run water in it but it works ok without.
 
I have one at .195. I think .250 is
doable but thin. Extreme tractor built
my pistons, talked me out of the.250
pistons for the use of my trailer
tractor.
 
Have done several at 5.75 never had a problem just make sure you use a block that has little or no pitting in the water jacket. Ones been pulling and plowing since 2001. Have to watch the temp if pulling it hard plowing. When tightening down the head I just go in 20 foot pound increments
 
According to JD only .045" as that's all they ever offered.

Many out there been running for years with larger ones though.
 

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