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View Full Version : KA sohc pistons into a dohc KA

ILiveToDrift
10-08-2003, 09:55 PM
Ok I searched and need a final answer. I have come to the conclusion that sohc ka pistons will go into a dohc ka without a problem and raise the CR to 11:1. But what I'm confused about is I also read that you have to mill them down to get the 11:1 CR. I was woundering if this is true? And if it is what does it mean to mill them down? Just wanted to know because I have a sohc laying around and want to put them into my 95 KA. If anyone has some final thought I would appreciate it.
andrave
10-09-2003, 08:40 AM
http://www.zilvia.net/f/showthread.php?s=&threadid=37774


might help you
misnomer
10-09-2003, 10:13 AM
y'know, all that post has in it is a link to the NICO forums :P

Anyhow, I searched quite some time on the NICO forums and didn't find many answers. Maybe I'm just bad at searching :P

I'm curious about this too.
Anyone? Anyone?
Startours7
10-09-2003, 11:05 AM
This is only what I think but wouldn't milling(shaving off metel)the piston it's self lower compression. I know on my Z car The head was silghtly warped so the shop had to mill the head and deck the block. Witch made the combustion chamber smaller. In turn higher compression.
So they might be talking about the head/block not thre pistons themselves.
Unless sohc pistons are not dished, I think dohc pistons are dished. If the sohc pistons are flat top then they would raise copression.
ILiveToDrift
10-09-2003, 11:24 AM
Now I have more information that conflictis with my first findings.

"Actually, the 89 SOHC pistons (stock 9.1:1 CR) would yeild a 11.6:1 CR, while the 90 SOHC pistons (8.6:1 CR) would give you a 11.1:1 CR."

I found this on NICO and I wanted to know if anyone can prove or disprove this? I thought they were all 8.6:1 CR.

As for me more searching I will do.
fogleroller
10-09-2003, 11:35 AM
The early 89's had the 9.1:1 CR

You can tell by the engine number, the head is different. Or, if the airbox does not have the extra sensor, then it's an early 89.

Late 89's and 90's had 8.6:1 CR

http://noclownz.dnsalias.net/s13/sohc.jpg
ILiveToDrift
10-09-2003, 11:45 AM
ok so after more searching I am pretty sure that the 89 pistons hace a CR of 9.1:1 making a dohc around 11.6:1.

I wanted to know if this was too high? I also plan on swaping 91 dohc cams first before it do the pistons. I also herd that it will be fine as long as I use 93 and up octain. I just want so input from someone that has done this.

Also if I use the piston rings from a 99 altima they work well with soch pistons.... or somthing like that. Well I guess I will have to search some more.
ILiveToDrift
10-09-2003, 11:48 AM
Thanks fogleroller that cleared that up. now for more searching I go.
misnomer
10-09-2003, 02:55 PM
aha!! The day is mine!!

The Infos! (http://www.zilvia.net/f/showthread.php?s=&threadid=23446&highlight=SOHC+pistons)
ILiveToDrift
10-09-2003, 06:17 PM
Yeah thats the post where I got the do I have to mill them down question. Well the sohc pistons come out tomorow and then I have to wait untill I find some good cams. Wish me luck.