Need Cam selection Help

[Nismo280zEd]

Ok granted, I did post this in the L6 forum and it's not for an L6 its for an L4. I have a 95 S14 (240sx) that uses the KA24DE engine. Basically a 4 cylinder z motor with dual cams. I'm having trouble selectiong the right cam for it.

 

The motor is gonna be built for mid to top end power, more than likely extensive head work. Larger valves, differents seats, mild port and polish to go with it.

 

I'm used to looking at Z cams and that's honestly the only cams i've dealt with hands on. The Z has high lift cams .400-.500 with 260 duration no problem. Do SOHC engines usually have higher lift cams to get everything to move? The S14, DOHC a race spec cam was listed as .401/272 this seems almost mild to me looking a Z cams. The one they list as a street/strip cam is .374/262 I'm relatively new to this car, but i figured somebody on here could guide me in the right direction on HOW to choose the cam i want for this motor. I've done CFM formulas and VE stuff and figured out all the air and all that good stuff, but it still doesn't help me figure out how much lift i need.

 

I did a search on here but only brough up schnieder cams, and some installs and V8 stuff, nothing about really how to choose one. If anybody body could show me the way I'd be greatly appreciative.

 

Thank you,

-Ed

[BRAAP]

Cam selection for multi valve engines is a little different than for a 2 valve design, well at least the lift and duration specs are different for a given power band on similar displacement 4v vs 2v designs.

 

Sorry I couldn’t be of much help on this one…

 

You might try the S-13/14 forums. There has to be an S-13/14 forum out there that has a few “honest” knowledgeable KA24DE guys on it?...

 

 

Good luck…

[Nismo280zEd]

yeah, problem is most guys just do trubo kits or sr20 swaps. I'm determined to do an N/A build... I must be just mental. Thanks though, atleast you replied.

[Alex_V]

yea an NA KA really isnt too productive, the most people have been able to get is 160-180HP. Its long stroke isnt very rev friendly. Now If you got the SOHC, theres a few options. Mostly because theres cams and alot of other parts for the SOHC block.

 

I have a 90 s13 with the SOHC and Im going to toss a small turbo on it. Im just looking for about 200HP, nothing to really get me in trouble, thats what my Z's for.

 

You can get the SOHC pistons and put them in your block and get 11:1 compression. That with the right cams would net some good power for not too much money. Still not more then 170-180 tho. KAs run about 120WHP stock.

 

OTOH theres always boost. A small turbo will give similar power but be very upgradeable.

 

Check out KA-T.org, freshalloy.com, zilvia.org (not sure on that one I dont go there much) lets see....then my 2 local ohio sites (ohiodrifting.com and ohionissans.com). AIM me and Ill put you in touch with some one that knows how to build a high HP SOHC.

 

Start searching Freshalloy, great side probably one of the best for nissan/infinity stuff w/o that bandwagon BS (only a little of it in the 240sx forums but LOTS of good info)

 

~Alex

[defrag010]

The amount of lift on a cam is proportional to the valve size. The number you need to find out for max lift on a certain valve size is the curtain area. Larger valves have a larger curtain area, and DOHC 4v heads have too small of a valve to have a large curtain area by themselves, which is why there are 2 intake and 2 exhaust valves.

 

Curtain Area = Lift * PI * ((Valve Diameter)-((Seat Width)*2*COSINE(SeatAngle)))

 

I don't remember what the forumla for the curtain area on a head with siamese valves (like 2 intake valves on a 4V head), but I can look at my notes later and get it.

 

*edit* nevermind, just read this site

http://www.araoengineering.com/4vs2.htm