Thread: boring an engine

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what does boring a block actually achieve besides more cubic inches?

Boring the block squares the bore, cuts out scores, and evens out the diameter of the cylinder bore.
I pulled a 283 years ago, that had one cylinder where the piston had worn down on one side only. The cylinder was scored, and almost oval in shape. The machine shop used that cylinder as the prime cylinder, and when it cut square, machined the other cylinders to match it.
Boring, aside from making the cylinder diameter larger, also removes any irregularities time has done to the cylinder. From this point, cylinder honing smoothes out the cylinder wall, and induces a cross hatch pattern to seat the rings.
I have seen boring jobs, where the entire cylinder bore was bored out, the remaining material threaded and a cylinder liner installed. I have also seen articles of boring out the cylinders, and pressing liners in. In this application, the center cylinders were welded together.

The displacement gains from boring an engine are typically minimal. At maximum overbore, a 350 Chevy becomes a 361. That's a 3 percent increase in displacement. A slightly more than mild 350 might put out 350 hp. In this situation, boring the engine might result in a 3% gain in hp or 10.5 hp. That isn't much and there are much better ways of going about it. By boring a block .060, you have just ended it's life. There is no more rebuilding it.

To me, in an application where having 10.5 more hp than the other guy makes no difference, a block should never be bored for any reason other than making the cylinders round, the walls straight, and to bring the cylinder diameter for the proper specs of the smallest piston that will fit in the bore. I just rebuilt my engine and had it bored to .020". If I burn it out, I can bore it .040, then .060. Going .030 means then next time you burn up your motor you have to go .060 and then your block is no good anymore.

yes i can not figure this one out .on e bay .125 over stock pass the big block selling for big money they are at the end of there life. and if you bore out to much you can hit water but if you do not the walls will move to thin and the rings will not seal . the wall help tie the top of the block the deck to the bottom of the crank case you are making it weaker i try to stop at 0.30 on small blocks and big block 396 at 0.40 big block 454 no more than 0.60 but this suff is getting hard to fined and good block are getting tuff to fine so look good be for you spend good money on junk. just be cause someome makes a pistons that size dose not mean you can bore it out that far 20 years a go i want the biggest big block in town so i sent out over 5 big blocks to get sonic check and one pass by the skin of it teeth that was when 4.250 cranks cost a lot of$$ so over bore was cheap way to get it up on CI

Originally posted by 76GMC1500
The displacement gains from boring an engine are typically minimal. At maximum overbore, a 350 Chevy becomes a 361. That's a 3 percent increase in displacement. A slightly more than mild 350 might put out 350 hp. In this situation, boring the engine might result in a 3% gain in hp or 10.5 hp. That isn't much and there are much better ways of going about it. By boring a block .060, you have just ended it's life. There is no more rebuilding it.

To me, in an application where having 10.5 more hp than the other guy makes no difference, a block should never be bored for any reason other than making the cylinders round, the walls straight, and to bring the cylinder diameter for the proper specs of the smallest piston that will fit in the bore. I just rebuilt my engine and had it bored to .020". If I burn it out, I can bore it .040, then .060. Going .030 means then next time you burn up your motor you have to go .060 and then your block is no good anymore.

This is sound advice, newbies pay attention!!!!!