Safe bore measurement?

I want to bore my b18a1 to 40 over, is that going to work or are the cylinder walls going to be too thin? Any ideas?

a common bore measurement among honda's is 20 over, 40 will take some modification for proper operation

you will possibly need to compensate the new dimensions with different piston rings

Yeah i'm doing new pistons and rings, the motor is a little out of round so i figured i'd re-do the pistons, rings, rods, crank, valves and springs. So the most you'd go is 20 over?

Depends on the compression. If you are using stock compression, and you don't try to drag it, I think you'll be fine. If you are going to race it, and/or raise the compression, you may crack a sleeve.

The only racing i'd do is the occasional 1/4 mile against buddies. It probably wont see much track action. Is it tru that if i replace the connecting rods i have to replace the crankshaft? i heard that somewhere but i wanted to make sure before i dropped some cash for the crank if i didn't need to buy it.

You don't have to replace the crank, just because you replace the rods. However, you need to plastigauge the bearing to crank journal clearance when you get them (with torque specified by rod rod bolt manufacturer). The stock bearing size from King bearings was within spec clearange for all the journals on the crank, even with a crank from a different block. Although it took me a bit to figure out, I needed to torque the rod bolts to the specs on the ARP rod bolts, not the stock torque for integra rods. The ARP bolts don't stretch as much, and with their lube, they require less torque.

However, if I had it to do over again, I think I'd just get stock rods. I don't really need the eagle rods I have, and I believe they are the same weight as stock. Don't quote me on that. ;)

As far as racing your buddies, I really think you'd need to take it easy on the engine if you bored it .040" over. In my opinion, you should only bore your block the amount necessary to make it round, and clear and scarring in the cylinder. You may save yourself a blown motor. I had mine bored only .015" over stock and then honed to fit my pistons. You see people selling their parts on ebay all the time, because they cracked their sleeves. .040" over would be a last resort because I was broke and the sleeves were focked. Otherwise I wouldn't do it.