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Maximum cylinder Bore Diameter

2272 Views 9 Replies 7 Participants Last post by  chrysler300le
Can anyone tell me the largest practical bore for a 360?, my machinist tells me that .060 over is ok. I recently installed a bored .060 over engine in my 83 RC and a cylinder wall cracked while I was idling in my driveway. Any ideas what might have caused this? I was just sitting there and it went bang, tap tap tap tap........ I took the heads off and the piston in that cylinder was cracked along the top edge. When I checked the bore with my finger I found the crack about 3 inches long along the length of the cylinder. I found another block but it is already .030 over should I have it bored or keep looking for a block?
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Someone will probably argue, but this is from How to Rebuild Small Block Mopars by Don Taylor and Larry Hofer, pg 43.

"As in the 273/318, the 340/360 will only accomodate a 0.040 in. maximum overbore"
i have to agree with cooper on this one. .040 is the max i would go on most any block. thing is about chryslers is that they can vary in cylindre wall thickeness by as much as .010 and that can be disasterous. although the machinist could be at fault for the issue you experienced i have run .060 blocks for years in the 10 to 1 range with no issues. i would be safe and stick in teh fourty thousanths area.

yea several mopar guru's have published books or articles saying .040 is the max without sonic checking the bores. My experience is most small blocks only need .020-.030" at 150K miles on the engine. If your going for max bore to get more cubes, think again cause thicker cylinder walls will make more power.
Stroke it
the only way to be sure is to pay for a sonic check
what you are looking for is whether the cores shifted when the block was poured
Evildriver-3 said:
Stroke it
You have a one track mind. ;D
Max cubes is not my reason to bore this block, just cleaning up the cylinder walls is. I am going to stroke the engine that I finally re-build. I hoped to get a different answer. What if I have all the cylinders sleeved.
Get another block
Its a bad idea to sleeve all the cylinders. Final machining could be way off. Also keep the cylinders as thick as possible with a stroker. They add more thrust on the cylinder walls.
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