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Discussion Starter · #1 ·
Ok during my entire time here at po.com this is my first post in the NA forum.

Anyways I have a question regarding the jdm h22a pistons with 10.6:1 compression ratio. I wanted to drop a set into my USDM h22a4 motor but I wanted to know if the bore sizes were compatible and which years work.

By the way I have a 2001 base if that helps.
 

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They're the same piston with a revised dome for additional compression. Are you attempting to make your car similar to 99PreludeLC to pick up some additional power? For the price you may just want to use the Type-S pistons at 11:1 but that's only if you can do some ballz on tuning.
 

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Discussion Starter · #3 ·
I already have someone offering to sell me a set of the 10.6:1 compression pistons. However someone replied to make sure wether or not my motor contained A or B size bore in order to find out if I could drop the pistons with no problem.
 

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Yeah, that was me. You can find the bore sizes for your current engine on the drivers side back of the block. It tells you in the Helms where to look. It will be something like "ABAA" or some other combination. You then need to find the proper number of A and B bore JDM pistons to drop in. You can tell what bore the pistons are by the stamp on the top:

No stamp = A
B stamp = B

If you can find a way to get JDM .25 over rebuild pistons then you could just bore your block out to .25 over and drop those in, but good luck finding them.

HTH
 

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Discussion Starter · #6 ·
Actually the Bore sizes should be the same because why would they make a diff mix of A and B bore size pistons?
 

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The reason for the A and B bores is to compensate for imperfections in manufacturing. The B bore is the smallest and is what is attained in a perfect peice. The A is a slight overbore put in at the factory to account for a minute error in the sleeve when it is installed. It is a type of quality control to ensure perfect fit. It just depends on how your engine was in the factory.
 

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Discussion Starter · #8 ·
So basically I have to look at my motor and see which bore size pattern it has. Then I have to find a set of Jdm pistons to match that pattern of bore sizes. Is there supposed to be a certain number of A and B sized pistons in my motor? If so can I just arrange a set of JDm h22a pistons to fit the pattern?
 

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Well your engine is going to have 4 pitsons (obviously) so ultimately you are going to have to get 4 JDM pistons. Once you have found out how many A's and B's you have you can source their JDM equivelents.

To find the bore letter you will have to look rather hard. Take as look at the diagram below, the letters will be stamped on a flat place on the block down where the head meets the block.

Front

Exhaust header
_____________
| |
| |
| |
|____________|
X
Intake Manifold

at the X.

HTH
 
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