iitywygms, i'm going to try to answer your question regarding the angular differences between the 4-tooth method for doing an exhaust cam swap to the intake side and using the jwt drilled cam gear.
here's the tech article for drilling your own jwt cam gear:
zerothread?id=199832
ok, let's draw up (either with compass & protractor or autocad or whatever) a model of the cam gear. since we're only concerned about angular dimensions, diameters are unimportant.
draw a circle. this is 360* of angular rotation.
there are 19 teeth on the gear, equally spaced. the angle between each tooth is approximately 18.95* (360/19 = 18.947368...) so draw a line from the center of the circle to the edge of the circle, measuer ~18.95* and draw another line, repeat until you've come around to the first line you drew. you should have a sprocket with 19 "teeth" now.
here's what it will look like (NOT TO SCALE!):
there are 9 holes on the JWT template. let's assume that they're equally spaced (which they aren't, you'll understand in a minute). so based on our assumption the angular spacing between the holes is about 40* (360/9 = 40). now, take one of the lines that you all ready have for your cam gear teeth, measure 40 degrees from here and draw another line, measure 40 from that line and draw another and repeat until you're back where you started.
here's what it should look like (NOT TO SCALE!):
now, if you start measuring the angular differernce between the cam teeth and the center line of the holes, you'll start to see the differences are about 2.1*, 4.2*, 6.3*, 8.4", and 10.5* on each side starting from the overlap starting line. this is what creates the advanced and retarded cam timing.
here's kind of what it will look like. note that i adjusted the angles between the holes and the teeth in order to get the nice advances and retards advertised on the jwt cam gear and again, NOT TO SCALE!
what you need to keep in mind when you use the jwt (or homemade) cam gear, is that it has nothing to do with the orientation of the original pin-hole for the cam gear. the degree of adnvance or retard is based on the relative position to the closest tooth on the gear, not it's distance from the original pin-hole.
so if you're doing a hot cam swap and you use the 4-tooth method,
DjPantsSpecR from page 1 wrote:the moral of the story is: 248 on the intake side is retarded 1.7 degrees. with a homebrew-redrill cam gear, or i guess a real live JWT gear, you can advance this by 2.5 degrees for a total of .8 degrees advance.
this looks to be much more acceptable, and would put a factory cam .8 degrees away from the nismo 248 intake cam, for much cheaper.
hopefully this answers your question or helps you understand it a little better.
Modified by DeXteR at 9:06 AM 11/20/2007
Modified by DeXteR at 9:07 AM 11/20/2007