Thread: Max Over-bore

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I have a SBC that's already 0.040 over that sucked a valve.......

Was thinking of using this block for a stroker project and go 0.060 over.

The engine would be going into a boat.

I have been advised the the max recommended over-bore for a SBC in a marine application is 0.030.

Was wondering what the opinion is here.......

Mercruiser used to have that reccomendation, never did know why..... Don (Itoldyouso) used to be in the marine biz, maybe he'll know. Should be able to go .060 on a 350....never messed with the 305's, no idea what they are.

Seems like the max recommended by everyone is 0.030", no matter the application. Us old guys are used to the thick walls of older blocks and you could bore them 0.060" with no problem. Nowadays with the thin wall casting technology used by the factories and instances of core shift, it's just not safe to do. Smokey Yunick said you need a minimum of 0.130" cylinder wall thickness all around, so if you sonic check the block and figure 0.130" wall will be left after boring and honing to size, go for it. Your walls would have to beep to 0.140" all around to qualify.

Heck, we used to bore the old Merc flatheads 0.187"-over to make 286 cubic inches.

thats why i love them 283s

Who is this Don (Itoldyouso)?.........is he on another forum..........sounds kinda familiar...

Originally Posted by ajv00303

Who is this Don (Itoldyouso)?.........is he on another forum..........sounds kinda familiar...

His last 500 posts......
http://www.clubhotrod.com/forums/sea...earchid=114909