21 stud flathead

37 Coupe said:
Myself if the block was good and crack free I would be looking into sleeving down or back to 221. Being a machinist I never got the concept of boring a size extreme to the original,most Barners it seems are in favor of doing this,you would never do this to say brake drums oversize beyond limits. I would rather have the dependabilty of a cooler running engine, I have a chart that shows a flathead engine from standard to .030 should be in normal heat range,0.060 should run 185F .0.090 over 195F and 0.125 over can get you 210 F.
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I would take issue with that chart. My engine is .125 over and runs very easily at 180. That's the stats that I use. Also comparing boring a block to turning brake drums is a little silly.
 
Regarding that chart. I'm sure no one believes that cast iron would be considered a good insulator, then how can it be possible that a .060 difference in wall thickness could produce 40 deg higher temperature? I don't think so.
 
flatjack9 said:
I would take issue with that chart. My engine is .125 over and runs very easily at 180. That's the stats that I use. Also comparing boring a block to turning brake drums is a little silly.
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I was just trying to show a comparison and this was the first thing I thought of. I worked for forty two years with knowing what was a standard size on various parts so I guess it is just a part of me to always try to be at that standard and not over or under whether an engine bore or brake cylinder or a rifle bore or anything designed and machined a certain size,way overboring is just not for me and only my opinion I guess.
 
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JM 35 Sedan said:
Walt, based on your experience, can a '36 LB block be safely bored over 0.060" or is it in the same category as a babbitted '36 and earlier 21 stud blocks? Just wondering.
Also, many thanks for being such a good teacher for us on these Flatheads!! Our visit to your shop during the Maine Tour was definitely one of the high points for me.
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John, no, the LB engine is just as thin as the earlier ones. A guy brought me 3 blocks a few yr's ago before I got one I could use and then I had to install a couple of sleeves. I did bore a 35 engine awhile ago to .080, Had a hard time to find .080 flattop pistons. The guy has put over 2000 miles on it and it runs great, no overheating. Walt
 
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