engine rebuild with SOHC pistons??

[Devens240]

hey i have a 91 s13 with a ka24de and im blowing blue smoke so im thinking my rings are bad and it may be time for a rebuild. if i use SOHC pistons to get higher compression will i have to have any tuning done? thankyou
Deven

[KiLLeR2001]

I think SOHC Pistons have a lower compression ratio than DOHC pistons.

[LA_phantom_240]

I think SOHC Pistons have a lower compression ratio than DOHC pistons.

No. SOHC pistons in a DOHC produces like a 10.5:1 or 11.1:1 compression ratio if I'm not mistaken.

From what I know, you'll at least need a tune, if not larger injectors and high octane fuel.

[Devens240]

you sure about injectors? and high octane as in premium pump gas?

[bbejj123]

i believe you might as well just buy high compression pistons for a dohc because if you use sohc pistons you will have to balance the engine

[s13 @ fullboost]

thats weird I hear people saying they put sohc pistons in there dohc cars because its lower compression and allows more boost but i guess not?

[Devens240]

i believe you might as well just buy high compression pistons for a dohc because if you use sohc pistons you will have to balance the engine

i have read alot about SOHC pistons and noone ever said anything bout getting the engine balanced?

[nicku]

well...if you have DOHC and use SOHC pistons, you will gain compression and you dont need engine balanced. but about the tune, i think you should search more about this.

[LA_phantom_240]

well...if you have DOHC and use SOHC pistons, you will gain compression and you dont need engine balanced. but about the tune, i think you should search more about this.

:bigok: I approve.

[Devens240]

lol ok cool i have asked on a few threads and some people went as far as saying i will need a bigger fuel pump as well as injectors? or could i just get an air fuel tune?

[LA_phantom_240]

I would recommend bigger injectors and a tune. You don't wanna run your stock injectors too hard or they'll fail, and its rebuild time again.

What's that saying about having time to do it right the first time, or having time to do it again?

[FRpilot]

thats weird I hear people saying they put sohc pistons in there dohc cars because its lower compression and allows more boost but i guess not?

lower compression pistons don't allow more boost. it's just safer to have lower compression to prevent detonation if you want to run an insane amount of boost. however, it doesn't matter if you have a good tune for your fuel maps.

optimally, you would want to get a compression ratio that is not too low and not too high if you have an idea of what turbocharger you're going to run and how much boost. higher compression ratio will help make more hp, so you don't want to go too low like 8:1, but not something crazy like 10.5:1 or 11:1 either.

as for sohc pistons, i wasn't quite sure so i didn't chime in. it's been years since i researched and read about it, but iirc the sohc pistons in dohc ka will increase the compression ratio because they are flat, while the dohc pistons are a dome tent shape.

i'm not sure. you should ask andrew bohan, because he went through a ka build for na and i'm sure he did a lot of reserach on it. he probably still remembers it, but doesn't feel like posting because this topic has been covered and you could just search for it. i'll im and see if he's willing to post. he'll probably post something funny instead of helpful if i show him this post. hahahaha

[Andrew Bohan]

[12:01] FRpilot: http://www.zilvia.net/f/showthread.php?p=2032812&posted=1#post2032812
[12:01] FRpilot: read my post, and see if yo uwant to help these fucking noobs out
[12:02] FRpilot: lol
[12:11] driftaholic17: eh, i'm good
[12:11] FRpilot: hahaha
[12:11] FRpilot: post somethign funny then
[12:11] FRpilot: be an andrew
[12:11] FRpilot: post "eh, i'm good"
[12:11] FRpilot: LOL
[12:12] FRpilot: eh im good, just search

[frosti108]

get your valve seals done lol


if you wanna run high compression, you should really upgrade your fuel system (better pump and injectors) as well as a couple pieces of tuning equiptment (atleast an safc and a wideband reader or a dyno tune)

[Devens240]

get your valve seals done lol


if you wanna run high compression, you should really upgrade your fuel system (better pump and injectors) as well as a couple pieces of tuning equiptment (atleast an safc and a wideband reader or a dyno tune)

ok cool new valve seals or grind the valves? and where should i get a rebuild kit?

[s13Carlo]

the SOCH pistons have the same compression as the DOCH pistons but the heads on the DOCH give ita higher compression with SOCH pistons, its liek 11:1 you dont have to run high octane unless you change your timing, and the bigger fuel injectors wouldnt be a bad idea but it will still run fine with OEM just less MPG