DIY KA24DE adjustable cam gears

[miked808]

Damn its been a while since I've been here but I'll be dusting the old girl off this weekend and finally get around to drilling those Cam Gears.

[DjPantsSpecR]

sexcellent.

oh and you dont have to drill all nine holes, i only drill a few holes on different gears.... i guess because i have 12 gears.....

but i make some only retard, or only advance, or sometimes only +/- 5 degrees or 2.5 whatever. And then i started using ym drill press.... now i jsut do them all

[keith0486]

ok stupid question but im not really a engine guy but how do adjustable cam/gears help with power wise i tryed to get myself an idea but im not good at getting ideas from reading im more of a hands on guy or tell me what it does and ill get it haha sry for the stupid question

[DjPantsSpecR]

That is a stupid question, and you should feel stupid. As far as im concerned you're a joke when it comes to life.

With that said (and im kidding, i hope you know this) adjustable cam gears make power WHERE YOU WANT IT. thats the entire premise. By modifying valve overlap, and initial reaction you are able to shift the powerband. More specifically the torque powerband.

Since horsepower ALWAYS equal torque *rpm/5252 you can always make more horsepower than torque at higher RPM. Since this is true, if you can bump up your higher rpm torque figures by shifting the power band north (usually with retard) the increased RPM and Torque will always net a better gain.

unfortunately, we're a little ways off from the correct cams and intake manifold to really start pulling high end power out of the KA24DE, its only a matter of time.

for now, on stock s13 cams (240/248) there is power to be made simply with gears. This raises the EGTs but makes power. On stock compression the raised EGTs are fine. on high compression, i found it to be a bit explosive....

[keith0486]

hey hey hey i told u it was a stupid question u dont need to flame on me lol just kidding i dont care if u do but thanx for explain it to me always good to know things so when it is time to upgrade stuff at least u know what it does and how it works and your not just doing it cause its something else one else is doing but thanx for your help

[neverlift]

That is a stupid question, and you should feel stupid. As far as im concerned you're a joke when it comes to life.

With that said (and im kidding, i hope you know this) adjustable cam gears make power WHERE YOU WANT IT. thats the entire premise. By modifying valve overlap, and initial reaction you are able to shift the powerband. More specifically the torque powerband.

Since horsepower ALWAYS equal torque *rpm/5252 you can always make more horsepower than torque at higher RPM. Since this is true, if you can bump up your higher rpm torque figures by shifting the power band north (usually with retard) the increased RPM and Torque will always net a better gain.

unfortunately, we're a little ways off from the correct cams and intake manifold to really start pulling high end power out of the KA24DE, its only a matter of time.

for now, on stock s13 cams (240/248) there is power to be made simply with gears. This raises the EGTs but makes power. On stock compression the raised EGTs are fine. on high compression, i found it to be a bit explosive....

what if one was to add a little fuel or maybe even soem water injection to the mix for the high egts? I'll be trying to source an egt gauge soon(new motor first now tho) its been on the list for a year now. lol what would be good to start with s13 cams? I'm thinking along the lines of -7.5I/-5(or2.5)E but I'm a newb on the cam shizzle. Just want the real pull to be around where sock falls flat(5300~5500 and up)I'll be playing soon enough I geuss

[d3vilskid]

Damn its been a while since I've been here but I'll be dusting the old girl off this weekend and finally get around to drilling those Cam Gears.

r those ur 240sx n da background got any spar parts on them

[d3vilskid]

hey i was just wondering something. I am gettin another 248 finially can put it on da exhaust side. so Ill be havin 248/248. Wat setup did u use da 248(+2.5)/248 or 248(+5)/248. Using the first do u noe wat it would net. Wat bout da second?

[Nisxsz]

OK. i know this thread is really old. I have a question. a chip like this found on ebay, http://cgi.ebay.com/ebaymotors...ZWD1V

would it help with the fuel map? dump little more fuel to compensate the cams?if i were to do 248(+5)/248

Thanks in advance.

[mrgreeneyes]

maybe im totally off, seeing as its 2:30am.. but, if you are drilling one hole in a gear that already has a slot to compensate for the weight of the pin that goes in it... arent you throwing the gear off balance by now making that slot just a "negative" weight now? or does it really matter b/c your cam lobes arent counterweighted either?

just thinking outloud kinda... any insight?

[DjPantsSpecR]

this is a really old thread... BUT i didnt see that chip you posted because the auction ahs ended. chances are it wasnt a "chip" at all and it was prolly just some useless resistor

"dumping" more fuel in, in conjunction with the cam swap, and advance might or might not be beneficial at all. The best use you'll get out of cam gears will be: on a dyno, with a wideband, adjusting ignition timing, and making fuel adjustments with either an ecu or a piggyback.

otherwise you just do it like i did, and try lots of different things, until you get something you're comfortable with.

to mr green eyes: the pin in the cam gear most likely isnt the same weight as the slot cut out of the stock gear, however, even if it is, the harmonic effect of the out of balance gear should be negligible.

If its that concerning, just drill out all the holes like on the JWT cam gear, this should keep things more in balance. however, the original question of it being out of balance because of the compensation for the pin would still exist.

if it was good enough for JWT, i assume its okay, but thats all i have to go by

[2FourTee]

Figured I probably posted this in the wrong thread. Just a warning for those attempting this:

I know this "DIY cam gear" idea has been passed around on here like herpes, but....I don't think people realize how small of a mistake you have to make to really mess up some DIY cam gears. If you are off by .008, you move the cam a full degree. I am sure some people have made semi-decent gears, but I bet most people's DIY cam gears are off by several degrees, and they don't even realize it. It's not like 90% of the people that do this are going to get a degree wheel and a dial indicator to make sure their timing is on.

I know I am not supposed to link to other forums, but I don't think this has been discussed here:http://www.ka-t.org/forums/vie...gears

Quote from smracing: "You do realize that if you are off only .008 (about 2.5 human hairs), it changes the timing a full degree. You are telling me that something that you printed off of something that was on the internet is good enough? And trust me, I know all about degreeing cams for ka's. I've done it many diffenert ways. I now usually use slotted gears with offset bushings. It is possible to drill your own, which I have done. Start by installing the cams with stock gears. Next calculate your actual centerlines. Determine how many degrees you need to move the cams, and drill new holes. This requires doing the math and using a mill with a rotary table or indexing head."

Quote above is from here: zer...setup

...

This idea has been around long enough that I am sure someone will call bull5hit or say I am lying. The proof is in the math. These gears are very small, with not much room for error, as far as cam timing goes.

So, if you do this, make sure you check it with a degree wheel and a dial indicator after installing them, to make sure you got it right. Otherwise, there's a very good chance they are off by several degrees.
Modified by 2FourTee at 5:24 PM 9/11/2008

[DjPantsSpecR]

Its not BS, when i made this write up I knew how people were going to use this:

some people were going to just drill by hand, and then go out and slap em in, and call it a day. You can be so inaccurate you might be retarding slightly when you think you're advancing.

Others would use a degree wheel, and see how the cams have changed. a .008 degree difference in that location will change it a degree. there is a TON of room for error here. You can drill a hole for 2.5, have it turn out to actually be 4 degrees, and make a mark and a reference. You wont have a step of 2.5 degrees, but it'll still be useful if 4 is what you're looking for, etc.

I'm more shocked about reading about other people on other sites etc who had no idea that doing this by hand could yield undesirable results. Isnt it fairly obvious? apparently not....

Drill your gears with a grain of salt?

[sticky_steve]

OK so I'm gonna bring an old thread back to life. I have a 93 block w 95 head and i just installed the 248/232 swap, and it feels great. But i was reading that i need to advance 2.5 degrees, but then the #1 lobes won't face directly to the outside. Is this correct and all i have to to is just loosen the bolt and advance it? Oh and by the way i did rotate ccw 4 teeth. Or am i mising something

[DjPantsSpecR]

Okay.

wrong thread; no you cant just loosen the bolt and advance it; and you are missing A LOT.

[sticky_steve]

Naw i got it figured out. U still a fan of 248/232?

[DjPantsSpecR]

nope. i'm mainly a fan of 240/248 these days/

with or without gears

[gingerbredman]

Making a post on here now is probably just going to be a "fart in the wind" but what the hey!?

Well, I thought I knew about the 248/248 swap when I did it back a year or so ago. I didn't even move the 248 int cam from stock position.. i know..

I've only got a couple remaining questions before I leave the cam stuff alone, for good probably.

Would using the 248/248 setup in either (2.5 or 5 deg) be notably more beneficial in a ka-t? *I'm with the stock setup as of now, except that I rotated my stock int. cam 1 tooth ccw. When I put my new head on, cams dead on stock, I had power up to 4.. low range blasted, but impractical mid-top end. So thus I rotated the int. cam 1 tooth.. I had done this once before in the past.

With the cams like so, power below 3500 is pretty much crap, but from there up is worlds better than what it was. Butt dyno against a 97 integra ls with vtech, cold-air, exhaust, header, test-pipe proved to be no match.

I'll just be honest here.. when I first did the 248/248 swap I fell in love with the lope. My 40 may have been slow as a 3-legged cat but it didn't matter. All the local honda guys would SWEAR up and down that I had a miss, that it wasn't the cams lol.

Anyways, it's late, I've gotta begin a ka transplant today, fix the single cammer and find a window regulator for the auto so I might have missed something.

Something I DO NOT get. Okay, when it's said that you " rotate the cam gear 4 teeth ccw" does that mean that the cam rotates WITH it? because that's how I had always interpreted it. But that wouldn't make a lick of sense since if you do that the cam itself will be facing 180* just about. I understand the drilling part and all that, it's just when you showed the picture of how the cams are supposed to look after installed with the drilled gear, it didn't look much off. I'd really like to do this, and being a machine student at school I'll be able to get things spot on..

Batman.. I just rambled like.. a book or 3..

[spooled240]

alright now i'm diggin this thread from 6 feet under but there's a lot of good info in here. As far as I understand the only difference between a 248(+5)/248 and a 248(+5)/232 would be WHEN the exhaust cam opens correct? I'm assuming the s13 exhaust closes 4 degrees after TDC just like the s14 cams in the following specs off the FSM:

Now this shorter exhaust cam duration..I'm not really sure what to think of it other than it's not going to be good for anything? I'm thinking the longer the valve is open the more air can be pushed out = more hp

my second question is the difference between the 2.5 degrees advance and the 5 degrees advance with the use of the 248 exhaust cam rotated CCW 4 teeth. This basically changes how much overlap you will have REGARDLESS OF WHAT EXHAUST CAM IS USED?

stock: intake is advanced 1 degree w/ 5 degrees total overlap.

2.5 adv: (2.5 degrees advance) + (1.7 degrees retard) = .8 degrees advance = 4.8 degrees over lap less overlap than stock? =/

5.0 adv: (5.0 degrees advance) + (1.7 degrees retard) = 3.3 degrees advance = 7.3 degrees total overlap

I want a powerband that will go to 7K which seems to be achieve with a lot of duration and overlap but for boosted motors I heard overlap is not really a good thing..but i'm thinking a 248(+2.5)/248 cam setup would be ideal? Not sure
Modified by spooled240 at 8:37 PM 3/21/2010

[Caveit77777]

Yeah I don't know much about cams and timing but after slowly reading this and comprehending everything, I'm pretty impressed. I'm not going to try it but I'm sure someone else will. Good write up.

[poneyrunner]

i just read through this whole post and another that linked me to this.. and im thinking of doing this.. and would love more info.. the pics done work on this link any more and im a very visual person.. any new info on this.. i have a 94 s13 de motor and i was thinking of swaping the cams.. i believe i have the 240/248 set up and was going to swap the cams to get the 248/240 setup.. my car is a drift car and i need the mid range and still want a bit more plus a bit more top end.. would the 248/248 setup be what i need or would i be better swaping my cams and where is this templete and i would love to do this but dont understand it yet without the pics and templete.

[tuner357]

Where can i get this template since the pictures are all corrupt?

[Razi]

I fixed the pictures.
I wouldn't do this DIY though, if you're off even slightly, you will be off by a degree.
$150 for a precisely machined adjustable cam isn't so bad.