Carbed high comp KA= PITA. But I am still crazy enough to want one.

[Tomakze]

So, I have been sitting on a high mileage KA24E for a couple years now, trying to figure out what my plans were for it. I know I want a bit more power than what the beasty puts out stock, but SOHCs are a bitch to build, apparently. I don't want anything crazy, I am happy with a motor below 200hp, so here is what I have come up with after lots of research... I want slightly higher compression, but still running street gas... the factory compression is pathetic. I am unwilling to let go of that amazing sidedraft sound/feel/look, so, carbs are in order. I have also learned that ignition systems are confusing...

 

Raising the compression on the SOHC seems unreasonably difficult and cost prohibitive.... however, using a DOHC motor with SOHC pistons *supposedly* kicks the compression up to a sweet 10.5:1. That should still be low enough for pump gas, I reckon. 91-93 octane should be fine, right? This would mean I need a DOHC motor though....

 

Thus far, I have had minimal luck finding a 240sx KA24DE around here for cheap. On the other hand, they are in every junkyard ever in the FWD variants. I already have the tranny/clutch/etc, and with the carb setup the intake and whatnot would not be used... is it possible to use a FWD block and SOHC stuff to convert it for use as a RWD?

 

I don't want anything crazy, my plan is to run better compression, Mikuni? (or similar) carbs, with a port matched head and a mild cam. Anyone have any idea what that might make power wise? I have seen people break into the 220hp range with similar but crazier setups, but they were running race gas and high RPM. I don't want that.

 

I have also seen aftermarket ignition systems on muscle cars that are running electronic ignitions without points... would this be an alternative to the L-series distributor swap? That way I can run the original distributor? If it isn't already painfully obvious, I am somewhat of an idiot about ignition systems. I just haven't put the time required into learning about them...

 

I am just in the planning stage (Read: broke) for now, but if i have some idea of what I plan on doing, i can start searching for good deals on parts and begin acquiring them. PLEASE let me know if anything I have posted is wrong, or if you know the answers to my questions. Thanks!

 

Oh, and FYI, I do not want a boosted engine. I want a carbed NA motor. Please do not waste my time telling me I am taking the harder approach... I know I am. I still want to do it, lol. NA cars just feel better.

[Tomakze]

If anyone wants to know why I want this setup, just look at this:

 

http://www.flickr.com/photos/34396089@N07/3373250699/

 

The owner is a Ratsun member, and has something very similar to what I want, sans the higher compression. I have found several builds, but not much information on the specifics. Tough wading through 25+ pages of "ohhh, that is cool!" lol

[philcas1987]

rebello oh yeah cheap roadster build huh? there was talk of vg33 pistons but i cant confirm. nissan comp catalog lists pistons

[datzenmike]

Early KA24E pistons (07 '88-10 '88), 12010-40F10 were slightly domed and the compression was 9.5. Much better for pump gas than over 10. They also come in oversize.

[metalmonkey47]

Weren't KA SOHC and DOHC motors a slightly different bore too?

 

I'd love to see that build documented. It's a very clean motor in the video and I bet it's rev happy.

 

 

For your ignition, why not ditch the points all together and set up a crank trigger ignition?

[Skib]

carbing a KA is easy.

 

for carbing the duel cam just use the stock dizzy and run something like mega jolt

 

I see lots and lots of good research done in your post but a lacking of understanding in some of the basics

[Farmer Joe]

the idea is good, other than the 10+ compression...

 

todays pump gas isnt like it was back in the 80s, 70s and so on... to get this to run right youll end up having to run AV gas or c12, vp100 or somthin like that to keep the pinging down..

 

ive done the high compression 4 cylinder, and its a pain in the fucking ass... compression just makes more heat than the engine can dissipate and you get pinging then..

 

if its going to be a driver, then id go with like lower 9s on the comp.. youll be able to run shitty gas, but still make some pretty good power..

 

focus on getting a cam that has a good power range, and flat torque curve.. get that air in and out.. people over rate high compression too often these days.. its not all about HP.. torque is what gets ya movin...

[Tomakze]

Early KA24E pistons (07 '88-10 '88), 12010-40F10 were slightly domed and the compression was 9.5. Much better for pump gas than over 10. They also come in oversize.

 

Really? The motor I have is from a '89 240sx... isn't that the first year? What would the higher compression pistons have come in?

 

carbing a KA is easy.

 

for carbing the duel cam just use the stock dizzy and run something like mega jolt

 

I see lots and lots of good research done in your post but a lacking of understanding in some of the basics

 

I do lack some basics, I know. This is a huge undertaking for me, and like nothing I have ever done before. Of course, this is how you learn, right? I have seen that megajolt ignition mentioned before, so I think I need to look into it... It sounds like it might be a better alternative to messing with the distributor.

 

the idea is good, other than the 10+ compression...

 

todays pump gas isnt like it was back in the 80s, 70s and so on... to get this to run right youll end up having to run AV gas or c12, vp100 or somthin like that to keep the pinging down..

 

ive done the high compression 4 cylinder, and its a pain in the fucking ass... compression just makes more heat than the engine can dissipate and you get pinging then..

 

if its going to be a driver, then id go with like lower 9s on the comp.. youll be able to run shitty gas, but still make some pretty good power..

 

focus on getting a cam that has a good power range, and flat torque curve.. get that air in and out.. people over rate high compression too often these days.. its not all about HP.. torque is what gets ya movin...

 

I used to work in a shop that built muscle cars, and they were building big block V8s with 11:1 compression and ran them on pump gas... I guess I figured the 4 banger would be no different.... My old z31 came with 9.5:1 compression from the factory, and it just recommended mid grade gas. Maybe I need to read more about how compression works?

 

I guess if I had a horsepower goal, it would be 160-180hp. I plan on spending a little time out on the local racetrack, and doing some autocross events. I just want enough giddyup to match the handling and braking abilities of the car. :)

 

Oh, yeah... at this point, I should probably change the name of my build. I think it stopped being "cheap" when I did the 300zx brake conversion.... lol

[Farmer Joe]

you hit it on the head.. the 4 cylinder is a completely different animal compared to what you mentioned..

 

the bigblock was built in a different time when they had good gas and didnt give a fuck about it.. they were deigned with that function in mind.

 

the z31, you cant really comare that since it FI.. it just knows how much fuel and timing to give it, and it has knock sensors to protect against pinging..

 

the KA, single or twin cam would be perfect around 9.5... i draw the line at that... with the carbs and cams, id still bet youd get at least 160-180hp... hopefully more torque than that too... in a roadster... fuck, thats gonna get some..

 

shit, i bet a stock KA in a roadster would scoot..

 

but its still your build.. i dont wanna impede on your decisions...

[Tomakze]

 

the KA, single or twin cam would be perfect around 9.5... i draw the line at that... with the carbs and cams, id still bet youd get at least 160-180hp... hopefully more torque than that too... in a roadster... fuck, thats gonna get some..

 

 

That would be the goal! :devil:

 

Thanks for the input... looks like I need to spend some time learning more about the basics... I thought my working knowledge was sufficient. That is why I post these things! I always learn something, even if all I learn is that I don't know enough! haha.

 

I guess that leaves two things...

 

1) Will a FWD DOHC motor work for my application?

 

2) *Sigh* what are my options for achieving 9.5:1 compression?

 

I do know that shaving the head is out of the question... it messes with the tension on the timing chain.

[philcas1987]

#2 i guess you cant read. go to the nissan parts department and buy a comp catalog. it will list the pistons you need. also the cam you need. oh yeah you dont have the high compression kae. its very hard to find. good giveaway is the harness doesnt have a intake air temp sensor

[Tomakze]

#2 i guess you cant read. go to the nissan parts department and buy a comp catalog. it will list the pistons you need. also the cam you need. oh yeah you dont have the high compression kae. its very hard to find. good giveaway is the harness doesnt have a intake air temp sensor

 

No need to be rude, I think it is very clear that I can read. So I assume that should get me the pistons I need for the KA24E, but I am still debating the DOHC variant. Seeing as how swapping in the regular SOHC pistons increases the compression, I'd guess those pistons in the comp catalog would put the DOHC over 11:1 compression. I like the SOHC because it looks more like the original engine, so that may be the route I take, but the powerband on the DOHC is sweet 'n smooth. I might have to stop by the local Nissan dealer and pick up that catalog. I was unaware that they still sold competition parts for the old KA's, let alone the SOHC. Parts counter people are usually idiots, and I am curious anyway... what car did those 9.5:1 pistons come in? 240sx, hardbody, what?

[Duke]

I'm glad that I could be of motivation. I have been running mine for the last 3 years and loving it. After some initial teething problems it now runs great. The car is my daily driver and I have had virtually no problems with it (after the few initial hiccups). As others pointed out previously, one of the main hurtles is the ignition, but there are a few options out there to solve this (megajolt, EL Dizzy converted to work on KADE, etc).

 

In regards to the availiblity of competition parts, the single cam KA is fairly widely used in SCCA club racing so the it is fairly well supported by Nissan. I don't really know about the dual cam engine though.

[datzenmike]

Early KA24E pistons (07 '88-10 '88), 12010-40F10 were slightly domed and the compression was 9.5. Much better for pump gas than over 10. They also come in oversize.

 

Really? The motor I have is from a '89 240sx... isn't that the first year? What would the higher compression pistons have come in?

 

240sx sorry i thought I mentioned that. Whether they are still available, I don't know.

[Tomakze]

I'm glad that I could be of motivation. I have been running mine for the last 3 years and loving it. After some initial teething problems it now runs great. The car is my daily driver and I have had virtually no problems with it (after the few initial hiccups). As others pointed out previously, one of the main hurtles is the ignition, but there are a few options out there to solve this (megajolt, EL Dizzy converted to work on KADE, etc).

 

In regards to the availiblity of competition parts, the single cam KA is fairly widely used in SCCA club racing so the it is fairly well supported by Nissan. I don't really know about the dual cam engine though.

 

Your car is inspirational! It is a very clean swap, something to be proud of for sure! Just curious, what kind of gas mileage do you get? Also, have you had it on a dyno?

[Duke]

I usually get somewhere around 25+ mpg. I don't know the exact number, but this is what I have calculated for the longer trips I have done. This is also with some fairly aggressive driving thrown in ;).

 

I have never had the car on a dyno. I have done some top speed runs with it though and after doing the aero calculations I'm guessing the motor is making between 160 and 170 hp. I could be totally wrong though. However much hp it is making, it's enough to have plenty of fun!

[Tomakze]

I usually get somewhere around 25+ mpg. I don't know the exact number, but this is what I have calculated for the longer trips I have done. This is also with some fairly aggressive driving thrown in ;).

 

I have never had the car on a dyno. I have done some top speed runs with it though and after doing the aero calculations I'm guessing the motor is making between 160 and 170 hp. I could be totally wrong though. However much hp it is making, it's enough to have plenty of fun!

 

Thanks for answering my questions! Both figures sound right in the ballpark I am looking for. Time to start the hard research so I can have one of my own! :D

[VintageRice]

Do it! I am almost ready to fire up my N/A Ka24e. Cant wait.

 

I just went stock compression. There arent many options for upping it.

 

Going to get a cam later. For now I'm going to tune the R1 carbs to the stock cam. Then swap it out later. Also got a 14lb flywheel and header.

 

Keep us updated!!

[Tomakze]

Do it! I am almost ready to fire up my N/A Ka24e. Cant wait.

 

I just went stock compression. There arent many options for upping it.

 

Going to get a cam later. For now I'm going to tune the R1 carbs to the stock cam. Then swap it out later. Also got a 14lb flywheel and header.

 

Keep us updated!!

 

Definitely! I will be posting any updates on it in my build thread. It will likely be a winter project, this summer is going to be about getting the car driveable, and then enjoying it. Of course, there is a lot of research to be done first, which is why this post exists now, and not later, lol!

 

What kind of header are you using? I was considering a cheap ebay header, since I might need to modify it to fit the roadster...

[VintageRice]

Definitely! I will be posting any updates on it in my build thread. It will likely be a winter project, this summer is going to be about getting the car driveable, and then enjoying it. Of course, there is a lot of research to be done first, which is why this post exists now, and not later, lol!

 

What kind of header are you using? I was considering a cheap ebay header, since I might need to modify it to fit the roadster...

I cut up a VW BAJA header and made my own. Then wrapped it. Turned out pretty good. Total cost around $60. Pics here ----> http://community.ratsun.net/topic/7862-r1-carbs-lots-of-pics/page__st__240

Trouble is most of the cheap ebay headers are stainless(go figure) and I can't weld it. The steel pace-setter(whick back in the day were the el cheapo header) are still almost $200.

[Unicornowner]

I DD'd a 93 240SX with the engine you're talking about. It had a shaved head, '89 single slammer pistons, with Dual cam rods. I ran an automatic ECU with an aftermarket FPR to set it slightly rich. I ran 2 exhaust cams instead of the stock setup. The exhaust cam has a slightly more aggressive profile when placed on the intake side. I had a total of about 11.2:1 compression when all said and done. If its run rich, there shouldn't be an issue. Put 91 or 93 octane in it and good to go. I don't know about the carb setup, because I've never done one. But the way I did it, it ran like a champ and put a completely stripped 240 into the 13s on the track.

[Tomakze]

I DD'd a 93 240SX with the engine you're talking about. It had a shaved head, '89 single slammer pistons, with Dual cam rods. I ran an automatic ECU with an aftermarket FPR to set it slightly rich. I ran 2 exhaust cams instead of the stock setup. The exhaust cam has a slightly more aggressive profile when placed on the intake side. I had a total of about 11.2:1 compression when all said and done. If its run rich, there shouldn't be an issue. Put 91 or 93 octane in it and good to go. I don't know about the carb setup, because I've never done one. But the way I did it, it ran like a champ and put a completely stripped 240 into the 13s on the track.

 

Impressive time! Well, there is more food for thought. I think I will try to get the high comp pistons for the single cam, and if that fails, DOHC it is. I have been pondering the SOHC pistons in the DOHC, and then run a water/meth injection system to keep it from detonating. Might be fun!