Quick question

[DRFT(kinda)]

Ok, so I'm floating around the internet looking at/buying parts for my KA build up and when I come across pistons I see that you can get over-bored pistons. This brings up questions in my head. First, do i need to get them for the motor (i am going to run a turbo) and 2, what needs to be done to the motor is i get over-bored pistons. Now, normally i would ask someone at the shop i go to, but i'm in iraq and that isnt an option. so thanks for the help.

[BlackHat]

I'm not 100% what your asking, but I'll try to anwser anyway.

Over boring the cylinders to accept larger pistons really doesn't HAVE to be done to run turbo. Actually, a lot of guys are running off of stock internals with a turbo (so obviously not overbored). When looking at new pistons the important thing to look for is lower compression pistons. I'm not sure what your goals are hp wise, so I can't suggest specific pistons (not that I could anyway).

Over boring your cylinders does raise the displacement of your engine. Which of course is a good thing as it allows more fuel/air into the engine. I don't think I'd overbore too much as the ka has a rap of having thin cylinder walls (Not sure how big of a deal this is, Ivan overbored .5mm and broke the ka-t record).

I would definately suggest researching a little more before choosing any pistons. You should have a good idea of what you want your end product to be before you start ordering stuff. Example: if you're shooting for 300+ whp you should also be looking for rods.

Hope that helped!

[fiznat]

Forged, lower CR pistons are usually offered in a slightly overbore size so that when installed, you can get a fresh cylinder wall as well. To install these pistons, you'll need to have the engine block re-bored with a fresh hone (cost is usually about $150ish). The idea is that the surface against which the new rings will break in will be completely fresh and score-free from however the engine was run beforehand. The overbore is usually minimal (almost always .020", called "20 over"), which does provide SOME extra displacement, but not really anything noticable performance-wise. The idea is to clean things up and help the rings form a nice, fresh seal.

How are things over there in Iraq? Coming home soon?

[DRFT(kinda)]

Hey, fiznat you actually hit the nail right on the head for what i was looking for. I was reading in an old thread about an engine rebuild and they were talking about overbored pistons. I've seen on all the site i've been to to order new pistons and rods the option of over-bored pistons and how much. You answered my question and now i can sigh a sigh of relief.

Iraq, well, lets just say things are complicated.