SOHC Pistons in DOHC

[shpaintball]

ok so i have a set of SOHC pistons that i want to put into my dohc ...anyone else done this....? how did it turn out?

[E7-S14]

I found this on some other forum site.. it might help

Heres the linkhttp://dgtrials.com/bbs/viewto...9317b

heres some excerpts

Nope -- putting the early KA24E pistons in a KA24DE gives you something like 11.6 or 11.7:1 (compared to the stock KA24DE 9.5:1). The later KA24E pistons will be something like 11.1:1 in KA24DE.Nope, I did the calculations myself based on numbers floating around the web.

It shouldn't be too hard to believe. The KA24E pistons have either a slight dome or dish, and even the slightly domed ones give a CR of 9.1:1 in a KA24E . The KA24DE pistons, on the other hand, have a significant dish, and give a compression ratio of 9.5:1 in a KA24DE. The conclusion, therefore, is that the combustion chamber volume of the KA24DE head is MUCH smaller than that of the KA24E, meaning if you put the KA24E pistons in a KA24DE, you get an even smaller combustion chamber.

Anyway, you don't have to take my word for it -- you can do the calcs yourself if you want.

the KA24DE head volume is 46 cc's (taken from Wiseco piston catalog)

the late KA24E pistons have a 2.8cc dish (found on a few datsun guys webpages) -- using this and the respective compression ratios (8.6 and 9.1) you can calculate that the early KA24E pistons have a 2.1cc dome

gasket thickness is .11cm

piston deck height is negligible (0.008cm in the hole if you want though)

bore is 8.9cm, stroke is 9.6cm

Hope this helped.. but remember that wasnt me writing that. it was on another forum site

[HaXoRsMoBiLe]

been covered here in nico as well, searching is a good start

[wa-chiss]

yeah, the SOHC pistons in a DOHC motor will net you SEARCH comp. ratio. hint, hint Been covered many times on this forum.

But Yes you can put them in, I don't know the accuall comp ratio it will be, and the search button is your bestest of friends on this forum.

[qat727]

I was searching for this same information a while back. I finally found enough to determine that it's supposed to work. I'm still in the final stages of assembly, but it seems to turn over and not hit.

Not to threadjack, but I couldn't find jack squat for info on the effects this mod has on fuel economy and fuel usage. I found several bits of guessing on using 91 and 93 octane, but no one seemed to know if it was mandatory. I also couldn't seem to find any information on any reduction on fuel economy. I'm sure it would reduce economy, but does anyone know how much? Am I just going to have to figure this stuff out myself by trial and error?

[wa-chiss]

well with close to 11.?:1 you will probably have to use 93 octane and retard the timing a crapload to not knock.

[qat727]

well with close to 11.?:1 you will probably have to use 93 octane and retard the timing a crapload to not knock.

Well, from the threads that searching was yielding, I was gathering that since there is a knock sensor built in, it will automatically adjust the timing to an extent to avoid knocking. The information I was getting was saying that premium gas was fine, but regular was out of the question. I couldn't find info on whether or not 91 was safe to run, though. If I end up knocking, I may just pull the whole engine back apart and put the regular pistons in.... or just sell the car.

[hannibal]

I dont think thats how the knock sensor works. I believe when the ECU detects knock, it alters the fuel and load maps or something,but I dont think it alters timing. i could be wrong on this, but if it were that easy, KA-T would have nothing to worry about.

High compression engines have more cylinder pressure (not as high as forced induction, but higher than a stock 9.5 motor). You should definitely use premium fuel.

I dont know how you tune (measure EGT??) a high compression motor, but dont just romp on it and see if it knocks. Youre a Honda guy, what do they do?

[qat727]

I dont think thats how the knock sensor works. I believe when the ECU detects knock, it alters the fuel and load maps or something,but I dont think it alters timing. i could be wrong on this, but if it were that easy, KA-T would have nothing to worry about.

High compression engines have more cylinder pressure (not as high as forced induction, but higher than a stock 9.5 motor). You should definitely use premium fuel.

I dont know how you tune (measure EGT??) a high compression motor, but dont just romp on it and see if it knocks. Youre a Honda guy, what do they do?

Far be it from me to guess how the knock sensor works. I haven't stumbled on an explanation, but I haven't looked, either. I was just under the impression that it detected knock, and it changed something. What? I don't know at this time.

And you're right, I am a Honda guy, but only stock. The only things I've messed with performance wise before have had a carburetor and 8 cylinders. I'll have to figure out if it's going to need tuning. From the initial figuring I've done, if it won't run properly at stock timing settings with premium gas, then I'll adjust spark timing and octane from there. I've heard enough people running this setup to make me believe it's feasible on pump gas. Just have to figure out which variety.

[hannibal]

BTW, that quote posted by 240Drifter is from a guy named Asad. He usually knows what he's taking about and the values seems familiar.

Early 8.6:1 KA-E pistons into KA-DE gives 11.1:1Later 9.1:1 KA-E pistons into KA-DE gives 11.6:1

[qat727]

BTW, that quote posted by 240Drifter is from a guy named Asad. He usually knows what he's taking about and the values seems familiar.

Early 8.6:1 KA-E pistons into KA-DE gives 11.1:1Later 9.1:1 KA-E pistons into KA-DE gives 11.6:1

Are you sure that isn't the other way around? I thought they lowered the compression on later engines.

And does anyone have a good way of checking which piston is which by looking?

[hannibal]

I'm not sure at all. I just know it changed and the early version wasnt produced very long...

[shpaintball]

thanks for the info....but is anyone doin this piston swap and having "good" results i know its no turbo but is it fun to drive?

[shpaintball]

the way you tell the sohc pistons apart are they are either flat or have a slight dome

[Dattebayo]

You can get about 180WHP with proper supporting mods like intake, exhaust, injectors and computer. ~20HP gained at the crank directly from the pistons is all you can get using 93 octane, you will never be able to run anything lower again. PERIOD.

But you will need to run race gas to get it to perform well. It will burn a little oil when it gets warmed up and you need to SEARCH the rest, because there are some things you need to mix from the DOHC that will not work with the SOHC pistons and vice versa.

I know this has been covered three or four times before, and I have personally built one using help from TrunkMonkey. Its fun if you do it right.

[shpaintball]

wait so i this is what i have ...the e pistons i later model so ill get 11:1:1 compression...now i can run it on 93 octane safely? as a daily driver? and what all do i have to do to just drop the pistons into the ka24de ...i have searched ....if you could tell me that would be nice

[shpaintball]

bump
Modified by shpaintball at 12:46 PM 2/4/2007

[Shift_Kouki]

You can get about 180WHP with proper supporting mods like intake, exhaust, injectors and computer. ~20HP gained at the crank directly from the pistons is all you can get using 93 octane, you will never be able to run anything lower again. PERIOD.

But you will need to run race gas to get it to perform well. It will burn a little oil when it gets warmed up and you need to SEARCH the rest, because there are some things you need to mix from the DOHC that will not work with the SOHC pistons and vice versa.

I know this has been covered three or four times before, and I have personally built one using help from TrunkMonkey. Its fun if you do it right.

I want to do this, but I want to do it right. Could you throw a little bit more information about your personal experience our way?

What else other than a piston kit does one need from the KA24E?? Are the DE rods compatible? Do I have to be careful which year SOHC pistons I get? What cam durations are compatible with the new pistons? What are my duration and lift limits? Will the S13 248/240 duration cams work?

Can you recommend any one in the DC metro area who could re-tune the car after the new pistons are in?

What kind of ignition timing am I looking at for 93 octane? What timing can you get away with on race gas?

I would totally If you can help me out with these questions I have.

[qat727]

I want to do this, but I want to do it right. Could you throw a little bit more information about your personal experience our way?

What else other than a piston kit does one need from the KA24E?? Are the DE rods compatible? Do I have to be careful which year SOHC pistons I get? What cam durations are compatible with the new pistons? What are my duration and lift limits? Will the S13 248/240 duration cams work?

Can you recommend any one in the DC metro area who could re-tune the car after the new pistons are in?

What kind of ignition timing am I looking at for 93 octane? What timing can you get away with on race gas?

I would totally If you can help me out with these questions I have.

I can not answer all your questions, but I just got finished installing the complete rotating assembly from a KA24E into a KA24DE. The connecting rods were the same length and width for both the E and the DE. I want to say the E rods may have been marginally thicker in the middle, but I was committed to using them anyway since I didn't have a complete good set of DE rods. The crankshaft from the E is slightly longer at the front, but this can be avoided by using the DE crank.

I am running the stock 240 intake/248 exhaust setup for the S13 and I have not encountered any clearance issues. From the information I could gather, running a 248 on the intake would put the intake valves too close to the pistons for comfort without fly cutting them. I did not try this to verify, however.

Not much from the E is able to be swapped over to the DE. The rotating assembly is about it.

I hope someone else can answer the rest of your questions. I'm still trying to get mine running properly.

[jdm_master_X]

Far be it from me to guess how the knock sensor works. I haven't stumbled on an explanation, but I haven't looked, either. I was just under the impression that it detected knock, and it changed something. What? I don't know at this time.

The knock sensor is a piezoelectric-type sensor. That means under a certain frequency (in this case, a vibration), the sensor will trigger the computer to slightly retard the timing accordingly to avoid knock.

[qat727]

The knock sensor is a piezoelectric-type sensor. That means under a certain frequency (in this case, a vibration), the sensor will trigger the computer to slightly retard the timing accordingly to avoid knock.

cool... now I know.

The E pistons in my DE seem to make it pull nicely when it's running right, which seems to occur at completely random intervals. I suspect the wiring on my car is completely shot, but I'll find out sooner or later.

[ken240sx]

turning the tables around a little bit....I'm curious what kind of compression ratios the DOHC pistons would make in the SOHC...possibly a cheap, easy way to lower compression to run more boost from a turbo on a SOHC.....I want to experiment...hmmm, i've got an extra set of DOHC pistons laying around and my buddy wants to boost his pignose......

ahhh, i could probably get answers searching but its 4am and im tired

[Shift_Kouki]

I can not answer all your questions, but I just got finished installing the complete rotating assembly from a KA24E into a KA24DE. The connecting rods were the same length and width for both the E and the DE. I want to say the E rods may have been marginally thicker in the middle, but I was committed to using them anyway since I didn't have a complete good set of DE rods. The crankshaft from the E is slightly longer at the front, but this can be avoided by using the DE crank.

I am running the stock 240 intake/248 exhaust setup for the S13 and I have not encountered any clearance issues. From the information I could gather, running a 248 on the intake would put the intake valves too close to the pistons for comfort without fly cutting them. I did not try this to verify, however.

Not much from the E is able to be swapped over to the DE. The rotating assembly is about it.

I hope someone else can answer the rest of your questions. I'm still trying to get mine running properly.

Good to know on the cam set-up clearing. Which year SOHC pistons are you using? 89 or 90?

[qat727]

It was my understanding that the engine I bought was from a 1989. I was also under the impression that the pistons were changed mid production in 1989, however this may be incorrect. As for which generation of pistons I have, I am not sure, but they have just a very slight dish.

[kamcam]

you said the crankshaft for the e and de aor not compatible ?

[DroptopDrifting]

hey qat727 did you clean up the block at all first? or did you just drop the pistons right in? i assume you had to get new piston rings for em but other than that was there anything else that you HAD to buy? and did you retard timing at all?

[240sRus]

Bump!

[sebazztard]

why

[White Comet]

i haven't met anyone yet that had this work out for them, ask didderson how it worked. not worth it, and if you ever want to go turbo forget it

[i240sx]

turning the tables around a little bit....I'm curious what kind of compression ratios the DOHC pistons would make in the SOHC...possibly a cheap, easy way to lower compression to run more boost from a turbo on a SOHC.....I want to experiment...hmmm, i've got an extra set of DOHC pistons laying around and my buddy wants to boost his pignose......

ahhh, i could probably get answers searching but its 4am and im tired

i would love to see this also