BigVinnie

iTrader: (2)

This thread was developed from years of research and information given in the Datsun/Nissan community. The information as stated is as close to being accurate as possible and there are overall varying differences between all s chassis motors that have left room for doubt or misconstrued information. All my information was received through Nissan, Mechanics that work on the KA24 engines, and through my own trial and error going through parts. I have tried to be as thorough as possible and my memory could be jumbled a bit with information, if in fact there needs to be a correction let me know. This is not ment to be taken literally as a Bible of any kind.

1989-1990 s13 KA24e SOHC 12VALVE
Between 1989 and 1990 there were 2 variants of the KA24e in the s13 240sx chassis.
In 1989 the KA24e used a raised dish piston allowing the KA24e to run a higher compression ratio than the 1990 KA24e. The KA24e uses a hemispherical design, rather than the KA24de's Pentroof design.

1989 KA24E specs:
9.1:1 Compression Ratio
Power Output:144 HP 5600RPM 155LB/FT torque @4400
1990 KA24E specs
8.6:1 Compression Ratio
Power Output:140 HP@ 5600RPM, 155LB/FT torque @4400

Low Points of the KA24e
One down fall to the KA24e was the short runner length preventing more power in the higher RPM range. Another down fall was that there are no oil squirter's used in the KA24E as there are in the KA24de engines. Oil squirter's are definitely a modification that should be implemented to such a large assembly of the KA24. The valve train of the KA24e needs to be modified to a solid lifter assembly. The stock assembly doesn't react well to high RPM use. KA24e's came with SCV's (swirl control valves)
High Points of the KA24e
Do to the low compression of the KA24e engines lower Octane fuel grades can be used without the cause of knock and ping. It's an economical engine that providing great gas mileage can as well run on cheaper lower octane fuels. Performance modifications and parts are less expensive. Being that it is a SOHC rather than a DOHC you buy half as many parts when it comes to cam swaps and adjustable cam gears. ECU tuning of the KA24e is very cheap and leaves much more room for making HP.

1991-1993 S13 KA24DE DOHC 16VALVE & 1995-1998 S14KA24DE DOHC 16 VALVE

In 1991 (actually august of 1990 production) Nissan made revisions to the SOHC block altering the block and changing the head for improved CFM's as well as the addition of an exhaust valve per cylinder, this would increase the overall curtain space of the exhaust valves which improves flow and efficiency for cam profiles. In addition the valve train was changed to use bucket hydraulics which makes it a much more efficient engine for high rev applications (same buckets valvetrain used in the CA18det). The additional exhaust valve not only increased performance, but helped to increase efficiency in scavaging. The long runner design of the intake manifold of the KA24de is used to increase higher power output which the KA24e was limited to. Down side to the KA24DE runners is that they are curved and it consumes more energy to move air through a curved runner rather than a straight runner. Oil squirters were added to all s chassis DOHC blocks. A knock sensor was also added to protect the longevity of the engine to knock and ping.
I always see in forums that people claim that the KA24de engines for s chassis are all 9.5:1 CR. This information I find to be invalid as OBD2 KA24de engines use a different head type than the OBD1 91-93engines.

Starting in the 1995 model years a CAS was to replace the old distributor ignition system of the obd1 ka24de engines.

1991-1993 engines use the G60 MAF, 1995-1998 engines use the G70 MAF.
Diameter of the G70 is larger than the G60. All KA24de engines use a 60mm TB, with 65mm taper.

1991-1993 KA24DE specs
9.2:1 Compression Ratio (Nissan Redline Claims 9.2:1CR)(FSM claims 9.5:1 CR)
Power Output:155 HP @ 5600RPM, 156 LB/FT torque 4400

Low Points of the 1991-1993 KA24DE
Only from the 1991 through some 1993 model years where SCV implemented onto the KA24de. In conjunction with the use of the scv's a longer duration cam was implemented labeled the 240/248 cam combo. On late 1993 PRODUCTION years the change went to 240/248 with a slight change in degree to the 248 exhaust cam. SCV's do add additional velocity at lower RPM's which increased lowend torque but would hurt high end HP power by causing an anemic reaction that restricts runner diameter. HICAS KA24de's are the slowest not do to cam profile unlike the 1993 engines, but are slower do to using additional power steering components for the HICAS system, this causes these KA's to have a much larger degradation loss than most standard KA24de's. Another low point of the KA24de is the use of a knock sensor which hinders performance at lower RPM's. Use of the knock sensor retards ignition timing and can sometime add more fuel to prevent knock and ping from occurring.
High Points of the 1991-1993 KA24DE
Due to the compression ratio of the engine the KA24de runs very well on 91 octane. With the removal of the SCV's the 91-93 KA24de's can now use a performance enhancement to use the 240/248 cam combo to it's full advantage. ECU tuning is also most effective in making power for the 1991-1993 engines.

1995-1998 S14 KA24DE specs
9.5:1 Compression Ratio
Power Output:156HP @ 5600RPM, 160 LB/FT torque 4400 RPM

Low Points of the 1995-1998 KA24DE
Now I can't misconstrue all the information. Not all 1995 model years are OBD2, many 1995 KA24DE's produced in 1994 were still OBD1 this allows for easy use of tuning the ecu unlike OBD2 which are a bit more difficult. The 1995 year OBD1 is more efficient in making power than the slowest of the 1993 model years, and utilizes advanced ignition timing to compensate for the 232/232 cam combo. As you can see the compression ratio as well as the use of the slightly larger diameter G70MAF, gained 4LB/FT of torque compared to previous KA24de years.
The down side to 95-98 models is that it lacks any type of superior enhancements as the engine is already maxed out in it's efficiency using the 232/232 cam combo. ECU tuning is difficult and is bound by many more smog emission disadvantages. In order to achieve high HP results high Octane grades must be used, and 96 Octane is the minimum requirement for performance and efficiency, unlike 1991-1993 which use a slightly lower compression can use 91 octane to achieve performance and efficiency.
High Points of the 1995-1998 KA24DE
The KA24de head for 1995-1998 models are far superior to that of any other KA24de head. The shrunken Pentroof design maximizes the flame front for maximum efficiency while increasing the CR compared to earlier KA24DE models. The 1995-1998 models can increase there performance by doing a swap of the 240/248 cam combo from earlier models.

Building Your Dirt Cheap NA KA Frankenstien
Now most of us Datsun/Nissan owners are either cheap engineers or cheap builders one of the reasons why we selected Nissan parts in the first place is that it is reliable and cheap.

So to start we will want to use a DOHC Block.
Next is piston selection which you should select the 1990 SOHC pistons as being a direct swap in to DOHC blocks.
Now if I was going to select a head from the DOHC blocks I would use the 1995-1998 since it is the most efficient head to use.
Then selecting cams I would use the 240/248 (keep it 240 INT, 248 EX).
Intake manifold I would select is obviously not one with SCV's.
For engine management I would go with OBD1 KA automatic tranny ecu 1991-1992.

Now what I've given you is just the basic build. It would be up to you to select injector cc type. As well as an upgraded MAF being either the N60 MAF from the Nissan Maxima, or the N62 MAF from the 300Z.
It would also be up to you to use either an SAFC, or to retune the ecu yourself.

Ranging from bore size, and depth of head gasket the compression ratio can vary from anywhere from 10.6:1 to 11.1:1 ratio.

MS!3

iTrader: (1)

nice write up vinnie. i found out that i dont have scvs. and my cam combo is 248/232 rather than 248/248 like i thought it was. haha mabey thats why i never understood why people say 248/248 is said to push the powerband to high. lol

clubredsilvia

BigVin, i have a 93' KA, that means that i dont have scv's, but i have a 232/232 cam combo. could i use the 240/248 cams out of a '92 KA and what would this achieve. Anything else to bring up the specs on a '93?

BigVinnie

iTrader: (2)

Yes it would. Although I don't know how much power installing those cams would be. I would assume that it would make more power in a OBD1 95 engine. But if worst comes to worst since your OBD1 you can also swap out the ecu to a 91 or 92 ecu to achieve more power with that cam combo. It will show gains, but I don't want you to be disappointed if it only shows maybe 3 or 4 HP on the dyno.

cronux

haha i tell vinnie to write a book, and he does a sweet writeup. schweet. so you're saying that the best head is the 95 and up head, and its good to have obd1 for mod'ing purposes, so the best of both worlds is the 95 obd1's right? and what about aftermarket stuff, i mean you mentioned some information about cams and stuff i didnt know about the different years, but how do those cams compare to aftermarket cams?

BigVinnie

iTrader: (2)

I don't know the EXACT dates when the head was changed and whether it was for OBD1 or OBD2 KA24de's I do know that looking at the majority of 95 heads they have a different number than the 91-93 heads.. But I will take a look at my friends 95 and check the reference numbers on the head, that way I can determine a date, I should be able to respond back within the week for this question.

cronux

okay, jeez. good quote time. "being a smart person does not mean knowing everything, it means knowing where to look"

ryguy

iTrader: (1)

God, I wish I knew what parts of my engine are 95 and which parts are 91. Good write up Vinnie, this needs to be stickied.

MS!3

iTrader: (1)

dont compare that much. most aftermarket cams have a duration on 260 and up. we have a 248 as our biggest cam. great for a mild street cam i guess. but id say they only makes about half as much power as jwt, bc, ect. using s13 cams is known as the poormans n/a setup. i am kinda interested what 248/248 would gain with a tune tho. haha this is new to me vinnie. for the longest time i thought i had that setup.

BigVinnie

iTrader: (2)

Really it is just where you would want your power to be delivered since a higher lift cam will usually drop lowend torque to sacrifice for higher HP gains.
I honestly like the streetable power that the OEM cams have to deliver. I would probably focus on internally building the engine to something that you could havedesired and work from that ( as far as cams).
The way I see it the KA reacts better to milder cams on to INT such as a 240, or even a 232. Problem with a 248 or even a 262 (Brian Crower Cam) is that the lift is open to long and there isn't enough modification to the intake manifold system or a higher compression (higher compression allows a stronger inlet vacuum for higher duration cams). Not to mention when you build an engine you focus on building from the ground up. A better bottom end with less harmonic disturbance can handle higher lifting cams better. In the case of the KA there is a lot of dwell time at TDC as well as it using a halfweighted crank.
I really think Nissan selected a good cam combination that isn't to different from the specs of the CA16de or the CA18det. Being that they use similar rod stroke ratio's the CA18det was an over achieving engine for it's displacement.
I find the 240/248 cam combo to be the best that Nissan could offer for streetability and power. The 248 onto EX was simply to increase scavaging and it makes an efficient overlap at high rev. I would find it better if people would stop thinking that bigger cam durations are better (such as the 248 onto INT), that isn't the case. It is what poses a sufficient overlap, and means of scavaging. In the KA's case shorter durations onto INT, and longer durations onto EX.

clubredsilvia

^^^ so basically, i should find a set of clean 240/248, or should i not worry about it and keep the 232/232(240/232?)

BigVinnie

iTrader: (2)

240/248 it's guaranteed power for OEM

Sqwibbs

What do you mean when you say “in order to achieve high HP results high Octane grades must be used, and 96 Octane is the minimum requirement for performance and efficiency" when referring to the 9.5 compression ration given by the 95-98 head?

Does this mean that, if we want to run pump gas with no boosters, we should forgo using the 95+ head?

My big plan this weekend was to go to Pick'N'Pull and to get an S14 headand a 91-92 ECU. Then ordering some BC264 cams and putting them in while I had the head out. However, now I'm not sure if I want the newer head because I insist on using 91 octane.

Also, I'm pretty sure my 93 doesn't have SCV's, is there any reason not to use its intake manifold?

Biggamehit

iTrader: (2)

Good stuff and i feell proud to say that i have owned every KA

BigVinnie

iTrader: (2)

Your fine using the 95-98 head even on 91 Octane. A 91-92 ecu is easy to tune and install a new chip (so is a 93 ecu it's just tuned for milder A/Fr's in stock form). You can in fact do mods such as the closed loop disable which hinders the knock sensor from signaling the ecu. Like I said the 95-98 head is far superior to that of the 91-93 heads.
I live pretty much 50miles from you so I know how uncomfortable it is to only have 91 octane as our only performance fuel, unless of coarse you go to performance shops, or infinion raceway which can carry blended octane fuel, or up to 104 octane.
The reason why higher Octanes need to be used on the 95-98 engine is because due to the tuning of the ecu (95-98 ecu's) the A/Fr's are matched to the 232/232 cam combination that the 95-98 engines use. Ignition timing is advanced to compensate the A/Fr's, and using the weaker cam combination limits any further performance using that combination, even on JWT tunes on the 95-98 engines you see very little performance enhancement with the 232/232 combination.
Now the reason why higher Octane fuels work well isn't always because it removes knock and ping, but since Octane burns slower than Heptane it increases compression and cylinder pressure creating the effect of more power during the compression stroke.
One method you can use to combat against knock and ping using 91octane and a 95+ head is to step up the plugs to iridium plugs and they do work great. You can also get a wide band O2 and an SAFC if you chose to and use the stock ecu tune, and add fuel to the fuel cycle, in this case you can use more fuel to your advantage to cool the cylinder charge and that also limits knock and ping.
I use the stock 91 ecu and an SAFC I have my timing up as high as 31 BTDC, and I've increased the timing which it has shifted my A/F ratio so I need to use the SAFC to add more fuel and cool the cylinder charge. It works great on cool 70* days, but when it it gets as hot as 90*+ outside temperature my SAFC shows as high as 50knock points and I can definitely feel a decrease in power. On days below 70* the SAFC can show knock anywhere from 0 to 10 knock points. So I am still limited with 91 octane and the environment isn't as controlled as it could be for the engine.
If the 93 production year intake manifold does not have SCV's use it, you will feel an increase in power.
Don't let anything discourage you from using the 95-98 head I think you will enjoy the power it produces even on 91 octane.