Some KA help

Alright, so I've bought a 91 KA for 50$ and I finished stripping it down to check for problems before I just throw it in a 240. Good Idea, seeing how the combustion chamber was completley filled with water, rust, and deposit. Nothing in there was left unscathed by the rust. However, after I got it all cleaned up, I'm left with a few questions.

There is some pitting on the cylinder walls, although no cracks. I'm assuming the rust ate away while it sat. I just need an unbiased opinion on if I should pay to get it bored out, try my luck with a ball/stone hone, or just buy a used block in good condition.

Also, I noticed that the pistons have weird numbers on them. They all have "02" on them, and below they have "04." Number one actually has "05" underneath the "02", but the rest have "04." I'm puzzled at the inconsistency and I suspect they could be oversized...but I didn't know they even made oversize for the KA, and that still wouldn't explain why 2 3 and 4 have only 40 over and number 1 has 50 over.... They pistons are dish-style, but I think that's stock for the KA.

*EDIT* I just measured the pistons with an electronic digital caliper and they all come out to be 88.2 mm. The stock bore is 89mm, so they can't be oversized. Although the markings are inconsistent, they all measure out to be the same size. I guess now I just need to decide what to do with my block.

Any input would be appreciated.

It really depends on how deep the pitting is. An expert should really be the ultimate decider. I would just oversize for the power increase. No idea on the numbers. Thats weird. maybe factory numbers for organization.

Thats a lot of honing, If you were to do this you would have to get oversized pistons to fit the cylinder, not that big of deal just some ideas.... personally I would go with what you said about getting a used block and possiably a used head with the amount of rust you were describing. but thats pretty much a whole new engine, so weigh out your options. Now that I think about it, should you trust the engine for making power with the rust weakening internal componets?

when honing a cylinder wall and replacing the piston with an oversized one you normally only going over .50 thousanths. Do the math a im pretty sure that you wouldnt even be able to get 40 additional cubic centimeters in displacement. in other words you dont feel a performance increase with the over sized pistons that will be fitted to the newly resurfaced block.

Note: any scoring of the cylinder wall more then .50 thousanths is usally not reparable with honing alone, bore and sleeve = fix.

besides, how far can a KA block go before the walls become too thin?

i have heard rumors that the ka cant be bored out any more then it already is, but honing a cylinder on average is only making it a 10th of an inch then it already is..... thats no where near getting the cylinder walls too thin

They sell oversized pistons for the KA. I mean, it is a cast iron block. Its probably pretty strong, but i guess a sonic test is the only way to find out.

Well I honed out the walls until the piston-to-wall clearance is 4 thousandths of an inch, measured with a feeler gauge. There is still some very very slight pitting, so I think it will be okay. The walls look like they were before I tried anything, they are by no means too thin.

good job, are you looking for pistons to fit, .20 over OEM specs or are you hoping that the ring expansion on the stock pistons will be enough to close up the gap?

Iv'e been told that .04 is the acceptable amount of clearance before the rings have trouble seating, so I'm just gonna run the stockers.

good luck