300 Cubic Inches?????????
Senior User
Joined: Jun 2002
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From: Lisbon, Ohio
300 Cubic Inches?????????
i wouldn't go more than about .060 over, because it is already a 4" bore. So unless you want some really big pistons, i would only go like .030 over and shave the heads like .010 over.
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Joined: Dec 1999
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From: Copley, OH
300 Cubic Inches?????????
300s can theoretically be bores to +.060, which would yield 309 CID. But the block is a thinwall casting and you should get it sonic checked before going that far. Holding the overbore to a bore realistic +.030 gives 305 CID.
Boring is a very impractical way of increasing displacement.
Clifford offers (or at least used to offer) a stroker kit that took the stroke to 4.375 which gives 330 CID with a stock bore, 335 @ +.030 and 340 CID @ +.060. With that much stroke forget about making high revs and count on having to do a lot of head work to get it to breathe. Dealing with Clifford there's also the issues of price (high) and delivery time (glacial).
Boring is a very impractical way of increasing displacement.
Clifford offers (or at least used to offer) a stroker kit that took the stroke to 4.375 which gives 330 CID with a stock bore, 335 @ +.030 and 340 CID @ +.060. With that much stroke forget about making high revs and count on having to do a lot of head work to get it to breathe. Dealing with Clifford there's also the issues of price (high) and delivery time (glacial).
Elder User
Joined: Mar 2003
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From: Colorado
300 Cubic Inches?????????
...is what you get at .030 over. Mine is 309.2 @.060 over (maximum overbore on a 300). I would have gone .030 over (or LESS), but the block was already at .040 . The more you bore, the less cylinder wall you have left which can create problems. If you go with the minimum bore you can spend your H.P. $$$ elsewhere (cam, carb/ intake, head, exhaust, ignition, gears ) . Then if you ever need to, you can bore it AGAIN.
Elder User
Joined: Mar 2003
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From: Colorado
300 Cubic Inches?????????
It's a TAD over 1.5 cubic inches PER .010 overbore. The geometry give you less for the 1st .010 and more for the last, but for all practical purposes - that's close enough.
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Postmaster
Joined: May 2002
Posts: 3,241
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From: Broken Arrow, OK
300 Cubic Inches?????????
A few years ago I wasted some time dreaming of a huge 300. Using a resleeved block with 400 SBC pistons and some creative crank grinding I think I finally got it to around 380 cubes. The down side was that it would cost several thousand dollars to actually do, and it wouldn't rev like somebody already said. It might not even be possible. Adding displacement is a horrible return on the dollar performance wise. The only practical time to spend money specifically for an increase in displacement is when driveability is limiting power production.
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Cargo Master
Joined: Sep 2001
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From: Canada
300 Cubic Inches?????????
you can go .060 over to 309 or you can go .030 over just to raise compression to 9.5:1 or 10:1 and have more power. mjust a thought. i wouldnt go more than .030 which is 305
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