1947 239 59A .040" Cylinder Over-Bore?

Ford1941

Ford1941

Member
In the process of restoring my 1947 59A 239 CI block, my machine shop has determined that an over-bore of .040" (40 thousands of an inch) will be sufficient to clean up the cylinder walls. Could someone confirm that the 59A block can safely be bored to this size (.040 over)? How much can this block actually be safely overbored? Any input is greatly appreciated. Thanks, Scott
 
Yes, the 3 3/16 standard bore 59 block will accept .040 over without much to worry about. The amount of maximum overbore depends on core centering and deterioration since produced. In most cases .100 over is safe and in some cases even more can be removed. Better safe than sorry when boring for your street car.
 
In addition to that, hopefully your machine shop is "sophisticated" enough to have access to sonic testing. http://raceology.com/2004/11/sonic-testing-what-why-how.html While many folks will honestly testify to having done similar overbores in the past, you're still dealing with old equipment that has probably had depletion from corrosion in addition to the variances of the casting process. Hopefully they magnifluxed for cracks as well, another frequent concern for our Ford flatheads.
 
I really appreciate all of the insightful answers. I will definitely ensure my machine shop does a sonic test and does everything possible to evaluate the integrity of my block. Thanks, Scott
 
Your machinest is clearly a youngster who has come up in the age in which a Ford V8 was meant to be discarded once it had reached .030. I think he will be startled by the readings he gets...
 
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