my comments on 248/240 s13 cam swap

Information on the naturally-aspirated KA24E and KA24DE engines.
RexAtHighSpeed
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alkemyst - thats a nice website with some good info but your calculator has a small error. When you retard the exhaust lobe the centerline value increases - that is not correct. Retarding the cam places the exhaust centerline closer to TDC overlap Which numerically decreases the exhaust centerline value. Retarding the intake cam increases the centerline value since it gets farther away from TDC overlap.

The best stock cam combination you can do in your 240 is the 248/248/110 @ 110. That means you'll have to advance the intake cam 12 degrees and retard the exhaust cam 10 degrees. You get almost all of the top end power but you also get a $hitload of torque. It has a choppy idle but hey, it runs everywhere!

Sorry for reviving a dead post but its worth it


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alkemyst
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Not sure on the decrease when you retard the exhaust cam...my calculator works like the ones on the manufacturer sites...i just added a database for the 240SX cams.

How can you get 12 degs adv though? Only gears I know of are JWT and have a +/-10 range.


RexAtHighSpeed
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alkemyst wrote:How can you get 12 degs adv though? Only gears I know of are JWT and have a +/-10 range.
DeXter did a great job (Here) of explaining how to calculate the proper location of the holes you need to achieve the advance or retard you want. You don't need to drill 8 holes in each gear. Just do the math and drill what you need. I wouldn't just eyeball it and use a hand drill on it. I have a 3-axis mill and I might just start selling the gears if I get enough interest (and gears are easy to get). I'd take it to a machine shop - probably wouldn't cost much and you can be sure it's done right.

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alkemyst
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RexAtHighSpeed wrote:
DeXter did a great job (Here) of explaining how to calculate the proper location of the holes you need to achieve the advance or retard you want. You don't need to drill 8 holes in each gear. Just do the math and drill what you need. I wouldn't just eyeball it and use a hand drill on it. I have a 3-axis mill and I might just start selling the gears if I get enough interest (and gears are easy to get). I'd take it to a machine shop - probably wouldn't cost much and you can be sure it's done right.
again though, how you getting 12 degs adv. Surely you have not tested this.

Bigvinnie
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Advancing 12 degress isn't possible on INT, because that would put MAX valve lift right at TDC between stroke 4 and stroke 1. However the intake cam can be retarded 12 degress. What you would need to do is retard the INT cam by 1 more tooth, then advance the cam gear 7degress to give a 12degree retard on INT.

360/19 tooth = 18.94 degrees between tooth count.Then Advance 7degrees on adjustable cam gear 18.94- 7 advanced degrees = about 11.94 degrees or almost the equivelant of 12 degress retarded.

Hype
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Bigvinnie wrote:Advancing 12 degress isn't possible on INT, because that would put MAX valve lift right at TDC between stroke 4 and stroke 1. However the intake cam can be retarded 12 degress. What you would need to do is retard the INT cam by 1 more tooth, then advance the cam gear 7degress to give a 12degree retard on INT.

360/19 tooth = 18.94 degrees between tooth count.Then Advance 7degrees on adjustable cam gear 18.94- 7 advanced degrees = about 11.94 degrees or almost the equivelant of 12 degress retarded.
Vinnie, no doubt you've done a lot of testing on this. Do you stand by your earlier claim that 240/248 (e.g. stock S13) makes the best power, or have you found something possibly better for NA power?

RexAtHighSpeed
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Bigvinnie wrote:Advancing 12 degress isn't possible on INT, because that would put MAX valve lift right at TDC between stroke 4 and stroke 1. However the intake cam can be retarded 12 degress. What you would need to do is retard the INT cam by 1 more tooth, then advance the cam gear 7degress to give a 12degree retard on INT.

360/19 tooth = 18.94 degrees between tooth count.Then Advance 7degrees on adjustable cam gear 18.94- 7 advanced degrees = about 11.94 degrees or almost the equivelant of 12 degress retarded.
BigVinnie, do you just make this stuff up as you go along? You obviously don't have any idea what you are talking about. You would have to advance the intake cam more than 120 degrees to have peak lift occur at TDC. Heres someone else who advanced the cam aggressively and lived to talk about it... http://www.240sxforums.com/for....html His car runs pretty well and he also put up a spreadsheet showing where his measured peak lift and valve events occurred at. Remember that the difference he saw between 3 teeth and 4 teeth retarded is in crank degrees. My car has the intake at 110 (ATDC) and the exhaust at 108 c/l (BTDC)

Bigvinnie
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RexAtHighSpeed wrote:
BigVinnie, do you just make this stuff up as you go along? You obviously don't have any idea what you are talking about.
You obviously don't read over your FSM then. INT valve in stock placement already opens 1degree prior to TDC. So if you advance 12 degress more on a 240 or 248 cam then the higher valve lift is at TDC...Thats not making it up, it's in the FSM, you can count the degrees yourself.

You can retard more than you can advance on a KA. If the stock position and placement began to occur later in stroke 1, then sure 12 degrees could be possible, but that isn't the case in stock placement.
Modified by Bigvinnie at 12:49 PM 12/22/2008

Bigvinnie
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Hype wrote:
Vinnie, no doubt you've done a lot of testing on this. Do you stand by your earlier claim that 240/248 (e.g. stock S13) makes the best power, or have you found something possibly better for NA power?
Yeah...If you can afford it PDM cams kick a$$. Other than that, no one to date has beat my stock NA dyno using 240/248 cams. Or Scotts dyno using 240/248 cams. when some one brings up a dyno with bigger HP numbers using the 248/248, then I'll believe it when I see it. Until then people are still trying to figure out INT cam placement of the exhaust cam 248....

sticky_steve
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Bigvinnie wrote:Yeah...If you can afford it PDM cams kick a$$. Other than that, no one to date has beat my stock NA dyno using 240/248 cams. Or Scotts dyno using 240/248 cams. when some one brings up a dyno with bigger HP numbers using the 248/248, then I'll believe it when I see it. Until then people are still trying to figure out INT cam placement of the exhaust cam 248....
So its obvious that you are running 240/248, but do you have any advancing on it or just stock location. Right now i have intake, high flow cat, and 3in catback. I'm running 248/232 with 2.5 deg advance on the intake,. Do you think that 240/248 would be better?

Bigvinnie
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sticky_steve wrote:
So its obvious that you are running 240/248, but do you have any advancing on it or just stock location. Right now i have intake, high flow cat, and 3in catback. I'm running 248/232 with 2.5 deg advance on the intake,. Do you think that 240/248 would be better?
My cams are in the stock position.

240/248 it much better tha the 248/232.

I don't know why people even consider using the 232 for the exhaust. It's a horrible cam to use on the exhaust. It reduces scavaging and exhaust pulse. It also limits the KA's rev range. You won't see a KA peak higher than 5800RPM with that cam on the exhaust.

FYI, the higher the lift and duration cam on exhaust the more effecient the engine becomes in making longer rev range and higher peak HP.

PDMs cams are an example of showing an extended rev range with a slightly higher lift and duration cam on EX, when compared to the INT.

sticky_steve
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Then I'm gonna change it out then. I tired of people "thinking" at 248/232 is better when you have done alot of research on the subject. 240/248 it is!!! thanks

warumono
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what would be the best for my car. Is a 95 s14 with obx pully kit, 4-2-1 headers 3" catback and intake. Should I do 248/232 or 248/240? I would like to lose as little torque as possible.


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alkemyst
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If I had a good 240 cam I'd go with the 240/248 in my S14 (1998)...the 248/232 did not make power at 2.5 adv or retard on the intake.

Now barring I somehow was sold a cam that's not 248 (didn't look like my stock 232 though) exhaust cam...I may have a coincidental problem...when I get time I will swap back to 232/232 or try and source a 240 cam. In the end I am debating selling this car and going to a 2006 GTO. The only thing left to replace in my car is my fuel pump. I was only making 120RWHP with headers, 80mm catback, 3" cat, NGK's, Accel wires, Injen CAI, new battery, improved grounds, 300zx fuel filter, timing played with (at stock timing I only net 108RWHP), etc.

Personally it's looking to me that most people that made the best power were using 240/248 cams. For every success story of 248/232-240-248, you will find 10-20 problem installs....and you are lucky to find any dyno proof other than the same 1 or 2 being quoted.

Bigvinnie
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alkemyst wrote:
Personally it's looking to me that most people that made the best power were using 240/248 cams. For every success story of 248/232-240-248, you will find 10-20 problem installs....and you are lucky to find any dyno proof other than the same 1 or 2 being quoted.
You couldn't of said it any better...

240/248 cams also happen to be the best for the s13 KA24de's with the removal of the secondary butterflys.

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gingerbredman
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i was thinkin.. a 248/248 setup allows for increased top end range, so i'm kinda thinking about throwing it back in for the turbo. would the stock cams hinder the power up top with the turbo considerably?

ugh.. i just want to get it right this time is all.

and as far as the butterflies go i have a couple Q's as i've heard so many opposing stories about them.

1. does removing them affect idle, or low end beyond concern?

2. the butterflies run off of vacuum right? if they do, what happens if the vacuum line isn't hooked up? do they stay closed?

Bigvinnie
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gingerbredman wrote:i was thinkin.. a 248/248 setup allows for increased top end range, so i'm kinda thinking about throwing it back in for the turbo. would the stock cams hinder the power up top with the turbo considerably?

ugh.. i just want to get it right this time is all.

and as far as the butterflies go i have a couple Q's as i've heard so many opposing stories about them.

1. does removing them affect idle, or low end beyond concern?

2. the butterflies run off of vacuum right? if they do, what happens if the vacuum line isn't hooked up? do they stay closed?
Nope, as a result you can see that OBD2 KA24de's run just fine without butterflys. The MAPS K and CAS values between OBD 1 and OBD 2 aren't that much different from each other. Ignition timing on OBD 2 KA's is just slightly more aggressive and offers a slightly different K value from OBD 1 KA's. Which is a dead give away looking at the differences in the diameter sizes between the G60 MAF for OBD 1 KA's, and the G70 MAF for OBD 2 KA's. So for OBD 1 KA's that aren't bound so much from base ignition timing the distributor can be advanced to compensate, if you can't use an ecu tune/modification.The end result in removing the OBD 1 butterfly's is that the brown solenoid located behind the head on the fire wall should be removed. Any vacuum lines before the solenoid should just be capped off.

I've decided to use a modified OBD 2 manifold that took about 18 hours to port, extrude and hone.......

Hype
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Looks clean man. Did you have it done at a shop or did you rig up some kind of system to push media through the mani? I hope you haven't touched anything else on the car since your last trip to the rollers. Interesting to know what benefit all your effort on manifold flow gets you.

Bigvinnie
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Hype wrote:Looks clean man. Did you have it done at a shop or did you rig up some kind of system to push media through the mani? I hope you haven't touched anything else on the car since your last trip to the rollers. Interesting to know what benefit all your effort on manifold flow gets you.
I did the work myself. Had to use a dremel snake to get into the runners.You probably won't believe how far off each runner diameter is stock. To ok alot of hours to make each runner consistent and of the same diameter.

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ddgsxr504
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Awesome thread, I'm gonna have to try this.

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gingerbredman
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I know you guys know more about the cam swaps than I do, so let me ask a question.

Why didn't my valves bend before, with the dual exhaust cam setup, not rotated at all on the cam gear? I simply took the stock int. cam out and dropped in the exh. cam. drove thousands of miles, power sucked, loped liked a mofo, never any noises or anything. All in all it drove fine, nothing changed except it got slower and sounder cooler

What I'm trying to figure out is HOW i bent 4 valves. i dropped the stock int. cam back in, a tooth off apparently because the power band sucked until 3500, then it rocketed.

The cam sprocket backed off, so the int. cam wasn't moving, or was it?? how could the int. cam sprocket backing out cause my 3 and 4 pairs of intake valves to bend???

I'd love to do this setup again

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i240sx
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so which cam will be best for single cam....is this just for the DE or wat... i try looking info for the E about cam swap..no luck....

sticky_steve
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All of these cams that are talked about in this thread is for the dual cam setup. If your looking for an aftermarket single cam then jim wolf technologies makes one for around $375.00.

http://www.jimwolftechnology.c...tID=2

I have no idea about the HP gains though. To tell you the truth about the single cam motor, if your looking to make big power on the single cam, then go boost. Its better to throw the same amount of money at boosting then it would be to try to go all motor.

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alkemyst
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sticky_steve wrote:All of these cams that are talked about in this thread is for the dual cam setup. If your looking for an aftermarket single cam then jim wolf technologies makes one for around $375.00.

http://www.jimwolftechnology.c...tID=2

I have no idea about the HP gains though. To tell you the truth about the single cam motor, if your looking to make big power on the single cam, then go boost. Its better to throw the same amount of money at boosting then it would be to try to go all motor.
boost is the way to may big power on anything. However some are just happy with a bit more power for a fraction of the cost

I know in dirt stuff the single cam KA's get crazy power, but it'd make for a terrible street car IMHO.

thefralix
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i did the 248/248 cam swap but dont really like difference from stock. if i go back to putting the stack exhaust cam(232) back in what do i need to do to set it up.

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alkemyst
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thefralix wrote:i did the 248/248 cam swap but dont really like difference from stock. if i go back to putting the stack exhaust cam(232) back in what do i need to do to set it up.
If you are using a proper 248 exhaust cam, your 232 exhaust cam goes right back in the same way...keep it in the same alignment.

I am going back to 232/232...I have been playing with 248/232 and I think my 248 cam is off or something, I have verified timing. Tried +2.5 and -2.5 and my power is down.

I recently did a vacuum reading and I am getting about 7-8 in/Hg at idle...far too low. It's got to be the cam is worn or a shim is off (I did verify clearances per the FSM and they were good).

We will see once I swap back Saturday and take it out for a drive on Sunday after the RTV cures.

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alkemyst
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idle vacuum is back to 15.9mm/Hg now...car seems to run better...too much church traffic today to get a good run in.


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gingerbredman
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Is anyone running a 248/248 setup on a ka24de-t? Ka-T will be sooon and I'm trying to finalize what cam setup I'll be running.

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gingerbredman
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oh..my...ballss.. I read through some and read some more and I think I damn near had a brain hemorrhage. Alas, I think I've found what I was looking for..

I'm determined to end this feud of homeless cams in my backyard

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nekoabandoned
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240/248 setup might be better for power up high , but for some of us doing show drifting in large parking lots it seems the increase in low end torque of the 240/232 or 248/232 would be the ideal setup.. correct me if im wrong


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