Quote:
Originally Posted by deuce_roadster
The Merc crank makes 10x more difference then the bore. If you are just driving around and not racing, I would leave it at .040. In fact, I have a NOS 59 series engine in my 40 coupe and left it with stock 3 3/16 bore, swapped out the crank for a 4" stroke, Ross pistons with metric rings, mild cam and 390 4bbbl Holley and it has LOTS of power. No way was I going to bore some life out if it just because I could.
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How could this be? A .125 overbore produces 258" engine with a stock stroke, while at 4" crank gives only 255" with a stock bore. Plus the stock stroke engine will have slower piston speed, which is more efficient. Sure flatheads are not high reving engines, but 10 times? I believe that figure is just hyperbole.