[Rick_Laycock]

Now I wanted to post this in the help section for a few reasons. I've been on this forum for quite some time and I haven't seen a 100% positive answer to this questions. I have read multiple threads that contradict one another.

*note I plan on editing this thread and/or perhaps make this a sticky so the info will always be around and easy to point to.*


Question #1. Cam gear differences. There are two types of cam gears, round tooth and square tooth. Now I have been told there is 4* difference swapping between the two. I am currently running a square tooth gear on a round tooth head (93' head). Now the question is would this make this the cam set to TDC 4* advanced or 4* retarded to start with.

Question #2. Which direction do you rotate the cam gear to advance or retard the cam timing. (is the 2nd image correct or reversed of what it needs to be?)


I'll post some awesomely drawn images to help depict this topic.

Additional Information.

Advancing the cam will give better low end power while sacrificing high end power. - Better for heavier car

Retarding the cam will give you better top end power while sacrificing low end torque. - Better for lighter car

 

[Rick_Laycock]

advance is always with the direction of rotation
retard is always against or opposite to the direction of rotation

Well this solves the first of the topics. So the above image would be correct as you are spinning the the cam gear the correct direction.

also , heh heh
there are early and late square tooth pulleys - I forget the years for each and the degree difference in their centerlines

as well as I think 2 different centerlines for the roller cams and maybe a couple of diff sets of pulleys for them too
?? Idono for sure - someone should

I suppose as long as we 'assume' the users are using the adjustable pulley it wouldn't matter what kind *early or late* for square or round gear. It would matter the cam which cam they are using.

it helps to know exactly what you may have before trying to call the cam "centered" 'cause it may not end up centered to what you think it is

example - my numbers may not be correct so don't quote em
early pulley , cl-108
314 cam , cl-110
late pulley , cl - 112

Sounds like a project I could work on for a while. Time to dig up some cam info and get it fact checked.

 

[Rick_Laycock]

from DDG: "There are 6 cam sprockets for the SOHC 2.2/2.5 family

1984-1988 "4201974" Square tooth 2.2 Turbo, 2.2 N/A
1984-1987 "4201992" Square tooth hi-output 2.2 N/A
1989-1992 "4387557" Round tooth 2.2/2.5 Turbo, 2.2 N/A
1989-1993 "4448690" Round tooth 2.5 N/A "common block"
1986-1987 "4273238" Square tooth, "tall deck" 2.5 TBI ONLY
1988 ......... "4387535" Round tooth, "tall deck" 2.5 TBI ONLY "

if you consider a TURBO cam "straight up",
then both the 4201992 and the 4448690 will provide 4 degrees of 'retard'

I've never seen the 'tall-deck' gears .. dunno what is special about them ?

I wonder with this information should we collectively decide a year or cam to put as the "base" cam and show the differences based off the change form the year to year / pulley difference vs the 'base' cam?