zeroGripS13

ok i was thinking.. i know u can use the kae pistons to raise the comp ratio.. i was wondering if anyone has tried milling the head to raise the comp ratio and if its effective or not..

thx

franman s13

yes you can mill the head for higher compresion but my friend who is a machinist told me its not safe to mill the head much, only enough for about .5-1 more compression point.

zeroGripS13

ok ty i appreciate the feedback ill keep that in mind if i decide to do it.. whats the ka stock comp ratio 9:1 isnit?

ArticDragon

89-94: 8.6:1
95+: 9.5:1 I beleive. Something around that. Don't mess with the shape of the combustion chamber. It was engineered that way, so don't mess with it. If you wanna up compression, chaange the pistons to higher CR pistons.

wikd240

dropping the combustionchambers from the stock 43 cc will not net you much in the way of compression... installing the sohc pistons will raise the compression ratio like it has been stated befor... but as big vinnie has pointed out doing so with a stock bottem end will make for more problems in the future... i am installing the sohc pistons in my ka24de but only after i have spent a lot of money inother departments... p&p of the head and intake manifold... jwt cams stiffer springs and stronger retainers... quality header and upgraded ignition system... im installing an msd 7al ignition system into the car along with a jwt ems with a cobra mafs... all this work is to gain as much horsepower as i can out of my na/ka...

zeroGripS13

thanks for clearing that up :P

BigVinnie

iTrader: (2)

98-99 KA24de frontier pistons wil raise compression to 10.3:1

NcTwOfOuRtY

just curious, im sure this question has been asked before, but if you put the ka24e pistons in the ka24de will you need to modify anything else? or will it work fine? i got a motor in a machine shop and its getting a rebuild, nothing all to fancy, but i would like to do some small minor upgrades. and it needs to be reliable. thanks

ArticDragon

They drop right in. Alright I'd prefer the frontien pistons. They seem more stable than 11:1 compression, lol.

98cwitr

thinner headgasket will work too

ArticDragon

Yeah, but dont mess around with the fundamental shape of the combustion chamber.

deviousKA

This is incorrect. The dish volume (as well as compression distance/height) of the 98-99 frontier ka24de piston is same as 91-98 240sx and yeild the same compression ratio.

The pistons are different in the 98+ ka24de frontier, but this difference is only in the rings. All 98+ frontier/altima de use thinner first/second compression rings, and thinner oil ring w/different depth. Rings are not interchangable between 240sx and 98+ altima/frontier ka24de piston. This is the only difference in the pistons. Frontier ka24de pistons use full float pin type unlike D21 Hardbody ka pin.

Dish volume/compression ht/piston pin is all the same.

BigVinnie

iTrader: (2)

Where did you get the info from. I am also a member of the 720 forums I also own a z24i. TLOOF who is an engineer calculated the compression ratio. He's pretty much the KA swap king of those forums. The heads of the rear sump truck series KA 98-99 are completly different from the front sump KA heads 91-98. It is the change from pistons to different heads that raise the compression. It isn't necessarilly the value and placement of the rings.
They are also interchangeable, with ring depth.....
People never thought it was possible to drop SOHC pistons into the DE's but it works.
That's just like saying I put an L18 head on an L16block to raise the compression. Maybe a bad example. But it was the design of the heads, not really the dish/rings in the pistons.
Not to talk down on you Devious KA I know you know alot, since you manage a nissan shop. But TLOOF is pretty good at what he does. I'll search through for the post and let you take a look.

240-kid

The SOCH Pistons can give you a higher comp.

BigVinnie

iTrader: (2)

WRONG!The compression ratio from 91-94 front sump ka's are different than the 95-98 front sump KA's.
The altima engine being front wheel drive does not share the same head as the 98-99 frontiers rear sump either.
I think you will come to find out that there are 5 types of heads, and 4 types of pistons designed for the KA, "SOHC and DOHC total". That isnt even including the naps-z pistons either. This also means that dish and rings will be different from different heads.
If you want to get completely rediculous with this debate you can interchange any of NAPS-z to KA heads, and even transfer an L20b head. All blocks of naps-z and ka share the same head bolt pattern. Down fall of naps-z, "it is a rear sump engine block", and can only be transferd from trucks, and with slight modifications into a datsun 510, slightly modifying the oil pan. Accept for the Naps-z20/22 designed only for the 81-83200sx. The internals as far as the cranks are the same forged cranks. This also means that all rods from any KA or NAPS-z are interchangeable, that is if you think you might have a "problem" installing pistons with different ring journals.
Any SOHC or DOHC KA head share the same bolt patterns, as naps-z, just to clarify things a bit.