what do you guys think about doing a bore? For a street driven truck is it a smart thing to do, or will you just ruin the longevity of the truck? Would .010, or .020 over be ok? Or if your doing a bore would you guys go big and do a .040 or .060 over?

 

I would personally say go as big as possible safely. There's no replacement for displacement. You will spool turbos easier, more torque. You may lose or gain mpg depending on your set up. I don't see down sides

 

If boring is needed go as small as you can get away with typically 20 over and 40 over is what you will go. Boring the motor out will not hurt anything as far as longevity is concerned.

 

Curious why you say go as small as possible, is it to keep as much block integrity? Is there a level at which integrity starts to decrease. I was always under the impression more displacment was better as long as strength is retained.

 

The more you machine out the less strength it will have. I'm not sure how these Cummins blocks typically fare ie. how much strength is actually lost, but its mostly just your choice on the matter. Personally I'd machine it the least amount that I had to and make up for the small amount of displacement I could of had by adding more boost. Just my 2 cents.

 

The thing about displacement is it builds boost. It's already there, Ya you can add more air or whatever but you gotta get to that point. Displacement is always there to make spool faster. I think if he reasearches what the safe limit of boring is its most advantageous to get the most bore that's safe. Spool and low end torque are what most people want. And displacement is the route of it all. I agree 100% on retaining strength but 5 cubic inches is better then none or whatever is possible to add

 

The cubic inch difference between std and .20 over is 4 CI which is not enough to make a noticeable difference in spool and overall power. The reason to only bore it what you need is overall strength and if you have to re bore again that is an option. Most piston options are either 20 over or 40.

 

Thanks for the input guys. Not sure what im going to do yet, just researching and this has helped. I definitely don't want to weaken the block, but want a good amount of hp.

 

boring the block is not needed to make a good amount of power. Only reason to bore the block is if you have to.

 

But I think youll make lets say 800-900 hp easier with a bore than without. Or am I wrong about that? With a wider piston it should be easier to support high torque and high hp