Need help with KA24DE piston spec

[duluthian]

Hello - I could use some help with the piston spec on the KA24DE engine. To cut to the chase, I'd like to know if I can machine 4mm off the crown's rim. From what I can see in images of this piston, it appears that the crown is dished. I've gone to junk yards trying to find an engine with the head off, but so far no luck finding one. And I can't find a machine schematic either.

The KA24DE piston is a very close match to the piston used in the Honda Ascot FT500. It has the same bore diameter and wrist pin diameter. The only problem is that the compression height is 34 mm whereas the Ascot's piston has a 30 mm compression distance. But the KA24DE's piston appears to be dished significantly. And I don't know if it is dished enough to take 4mm "off the rim." If it turns out that the dishing is about 4 mm and the remaining land-to-ring distance would tolerate the trimming, well, we probably have a winner.

Any assistance in this matter would be greatly appreciated. What would be doubly appreciated would be if anybody out there could provide a link to a machine schematic of the piston. That might be asking much, but I'm trying to find out this info.

Thanks in advance,

geo

ps - why am I doing this? Well, Ascot pistons are getting very, very hard to find. Wiseco makes a high compression piston for it. But if you're trying to keep the engine as a happy go lucky, run on regular engine, options are very limited.

pps - I know this should go in the tech & engineering forum. I did originally post it there. It's not a highly trafficked blog.

[frapjap]

Pics of your (presumably) broken pistons?

(I know, I'm not of much help)

[Dattebayo]

4mm is a lot. You'd lose so much piston surface thickness that the first couple rpms would probably blow through the top.

[IanS]

If you are in Duluth, which your screen name might suggest, you could always swing by my house. I have a set of SOHC KA pistons, DOHC KA pistons, and Nissan Motorsports High comp DOHC pistons, all sitting on my work bench. Measure what you want.

4mm is a lot. You'd lose so much piston surface thickness that the first couple rpms would probably blow through the top.

The DOHC pistons do have a lot of dish..... It may be possible. Quit being such a negative nancy.

[Dattebayo]

Well, to be sure, does anyone have real specs on how much meat there is between the underside and the top?

Got a spare DE piston you care to drill through and measure?

[IanS]

I kind of do actually. Have no need for the stock DE stuff when I will be using that high comp stuff, and keeping the SOHC for spares.

[duluthian]

[quote="FlatBlackIan"]If you are in Duluth, which your screen name might suggest, you could always swing by my house. I have a set of SOHC KA pistons, DOHC KA pistons, and Nissan Motorsports High comp DOHC pistons, all sitting on my work bench. Measure what you want.

FlatBlackIan - thanks for the helpful reply. My fiance lives in Esko and I'll be there this weekend. Please contact me offlist so we can coordinate. My email address is: [email protected]

geo

[IanS]

Email sent

[Dattebayo]

I'd kind of like to know this too. I've always been told it was only the SOHC piston that could be milled in this way.

[IanS]

I'd kind of like to know this too. I've always been told it was only the SOHC piston that could be milled in this way.

We will be getting to the bottom of this tomorrow. I will have both side by side to look at, so we shall see. I no longer have the high comp pistons here though, as they went with the head and block to the machine shop to have some honing and decking done.