stock compression ratio

[91s13coupe]

there seems to be some inconsistancy as far as what the stock compression ratio is on a dohc ka. ive seen 9:5:1 and 8:6:1 on so cal 240sx.org website that looks like its a page from a nissan guide. what is it?
also i just did a compression test on my 91' and all four were at 160psi. im wanting to turbo this car over the winter and just thought i would check to see if the engine was up for it. those numbers are good right?! this thing runs great and has 174k miles on it!!

[Steeles]

those numbers are good for a compression time to turbo that KA

[240fluke]

DOHC KA engines ('91-'98) had a 9.5:1 compression ratio. 8.6:1 would probably make for a good turbo setup though, but that is not the compression of any year DOHC 240 engine. IIRC, the KA24E ('89) came (IF you were lucky) with a slightly juiced 9.1:1 or 9.2:1 engine (early model engines). Then '90 KA24E engines were all like 8.6:1 compression (maybe 8.9:1, but I think it was 8.6:1, someone can verify that).


If you are looking to turbo that engine, that looks to be pretty good compression on your engine. I would probably recommend beefing up the bottom end and doing at least a minor rebuild of the engine though (since it has so many miles on it). Good luck with the turbo.

Tim '95 SE

[91s13coupe]

thanks for the info. i thought that was pretty good compression for a ka with 174k miles on it. hopefully over the winter i can get this all done.

[240racer]

has anybody considered the possiblity that the factory build may be better then a rebuild even with fairly high miles??
It's one thing if you are changing pistons, but if you aren't...

[91s13coupe]

good point! im sure factory is alot better as far as that goes.