Topic: boring a Flat Head


windjamer    -- 09-05-2011 @ 2:28 PM
  How much can you safely bore a early 59A, and secondly howmuch can you safely bore an 49 to 53?


oldford2    -- 09-05-2011 @ 2:52 PM
  I think a "safe" answer is the minimum possible to clean the bore. I bore to the minimum. If you are thinking about boring to the "maximum" to increase displacement to get more "power" on a stock engine, forget it. You could not tell the difference between .040 and .125 in performance. IMO
John


supereal    -- 09-05-2011 @ 3:03 PM
  At our shop, we don't recommend over boring more than necessary to clean up the bore and leave enough stock to hone to standard oversize, usually not more than .060. Once you get past that size, special pistons are generally required. As pointed out above, over boring doesn't produce enough additional power to justify the cost. The best method is to install a four inch stroke crankshaft, if you can find one. Be sure that, if you bore, that an adequate crosshatch honing pattern is provided to allow ring seating.


deuce_roadster    -- 09-05-2011 @ 4:02 PM
  In addition to the good advice above, make sure you use a machine shop that is familiar with flatheads. (I have seen blocks decked at the wrong angle and ruined) Due to rust issues and core shifts you should sonic test each cyl in at least 4 places to determine how much thickness you have left to work with. My guy doesn't like have less then .100 anywhere when all the machine work is done. This test is well worth the expense to help eliminate surprises later.
Good luck!


Stroker    -- 09-05-2011 @ 4:06 PM
  Back in "the day"; we would bore blocks out immercifully, because if we ran into "water", we'd simply make another trip to the junkyard. Today, that option is not available, unless you wish to spend thousands on an aftermarket block, such as Don Ferguson III, has created. If you wish to build a racing engine, there are folks that can accommodate your needs. If you are simply trying to enlarge your existing engine, you probably shouldn't go there, and follow Super's advice to only bore the block the minimum amount needed to get decent cylinder sealing.




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