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cobra1923 · 05-09-2008, 06:12 AM

Yes, you can do both at the same time. Boring is making the holes larger in diameter (requires larger pistons) but it typically doesn't net you a whole lot other than nice new cylinder walls. You will here boring referred to as .030 over, .060 over, .090 over.. A 302, bored out .030 over becomes a 306. The thing to also keep in mind that is the more you mill out of the cylinder walls, the thinner and weaker the walls become and there is less surface area on top to hold you r gaskets in place. Stroking on the other hand, is typically putting in a different crank that changes the distance the pistons travel within each cylinder and can net some huge displacement gains. There is ususally clearance issues that need to be addressed withing the block so that the larger crank has room to spin without meeting the block. One of the favorite "old school" stroker motors is a GM 350 block with a GM 400 crank, you retain the wall thickness of the 350 but you get 383 inches of displacement b/c the cylinders travel further down on the intake and combustion stroke and go further up on the exhaust and compression stroke (unless you change the heads (combustion chamber volume) you will end up with a higher compression also).
As far as what's better? As I mentioned earlier, boring nets you very little from a performance perspective other than nice new cylinder walls, thus factory fresh compression (with new rings and the correct oversized pistion).. you can play with the pistons and add a dome to bump up the compression when you do a bore and it will get you some more power (and require higher octane). If you have an old worn out motor, then a rebuild with an overbore is very nice. Stroking is more involved with the machining but gets some great torque added. There are some tried and true packages out there from a couple of merchants for both our 5.0 and our 4.6s... If you're doing the stroker motor, it only makes sense to get a little .030 over-bore to clean up the cylinder walls (and add a couple more cubes). There's obviously a ton of other aspects to consider and this is about as far as my knowledge can take me.. I did one 347 quite a few years ago and it was a no-brainer package (dropped the block off at the machine shop and got all the other parts in the mail to put it back together)

Hope it helps a little

05-09-2008, 06:12 AM	#2 (permalink)
cobra1923 Senior Member Join Date: Nov 2004 Location: Baltimore Posts: 527	Yes, you can do both at the same time. Boring is making the holes larger in diameter (requires larger pistons) but it typically doesn't net you a whole lot other than nice new cylinder walls. You will here boring referred to as .030 over, .060 over, .090 over.. A 302, bored out .030 over becomes a 306. The thing to also keep in mind that is the more you mill out of the cylinder walls, the thinner and weaker the walls become and there is less surface area on top to hold you r gaskets in place. Stroking on the other hand, is typically putting in a different crank that changes the distance the pistons travel within each cylinder and can net some huge displacement gains. There is ususally clearance issues that need to be addressed withing the block so that the larger crank has room to spin without meeting the block. One of the favorite "old school" stroker motors is a GM 350 block with a GM 400 crank, you retain the wall thickness of the 350 but you get 383 inches of displacement b/c the cylinders travel further down on the intake and combustion stroke and go further up on the exhaust and compression stroke (unless you change the heads (combustion chamber volume) you will end up with a higher compression also). As far as what's better? As I mentioned earlier, boring nets you very little from a performance perspective other than nice new cylinder walls, thus factory fresh compression (with new rings and the correct oversized pistion).. you can play with the pistons and add a dome to bump up the compression when you do a bore and it will get you some more power (and require higher octane). If you have an old worn out motor, then a rebuild with an overbore is very nice. Stroking is more involved with the machining but gets some great torque added. There are some tried and true packages out there from a couple of merchants for both our 5.0 and our 4.6s... If you're doing the stroker motor, it only makes sense to get a little .030 over-bore to clean up the cylinder walls (and add a couple more cubes). There's obviously a ton of other aspects to consider and this is about as far as my knowledge can take me.. I did one 347 quite a few years ago and it was a no-brainer package (dropped the block off at the machine shop and got all the other parts in the mail to put it back together) Hope it helps a little __________________ 2003 10th Anniversary Cobra Convertible All Stock and staying that way... well maybe some pipes since it's so quiet..ahhhh! it's a sickness 1995 mustang GT vert - all black (almost back together)