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tubman · 02-29-2020, 01:33 PM

I don't know what this prejudice against boring is all about. An 1/8" overbore will give you 258 ci (3 MORE than a Merc crank with a stock bore) and lower piston speed (which is always good). The pistons are about the same price as a set of stock pistons, which is a helluva lot less than a Merc crank and any required preparation. I have never done a French block, but from everything I hear and read, they are better than a garden variety 8BA, which will take a couple of overbores past 3 5/16" easily. Plus, you can always do a hone or two in between.

How many re-rings are going to have to be done to a carefully assembled, meticulously maintained engine that gets a couple of thousand miles a year on average? By the time the bores are worn out in a couple of hundred years, the guy currently owning it will probably be able to whip up a new block on his home 3D printer in 15 minutes.

Every time I see a post about "saving the engine for a future rebore", I have to wonder. Maybe for some of the 3 3/8+.030 or 3 7/16" (yep, some guys did it) bore engines out there, but for a stock bore? I don't see it.

02-29-2020, 01:33 PM	#7
tubman Senior Member Join Date: Dec 2013 Location: Minnesota, Florida Keys Posts: 10,319	Re: 3.75 versus 4 inch crank I don't know what this prejudice against boring is all about. An 1/8" overbore will give you 258 ci (3 MORE than a Merc crank with a stock bore) and lower piston speed (which is always good). The pistons are about the same price as a set of stock pistons, which is a helluva lot less than a Merc crank and any required preparation. I have never done a French block, but from everything I hear and read, they are better than a garden variety 8BA, which will take a couple of overbores past 3 5/16" easily. Plus, you can always do a hone or two in between. How many re-rings are going to have to be done to a carefully assembled, meticulously maintained engine that gets a couple of thousand miles a year on average? By the time the bores are worn out in a couple of hundred years, the guy currently owning it will probably be able to whip up a new block on his home 3D printer in 15 minutes. Every time I see a post about "saving the engine for a future rebore", I have to wonder. Maybe for some of the 3 3/8+.030 or 3 7/16" (yep, some guys did it) bore engines out there, but for a stock bore? I don't see it.