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Discussion Starter · #1 ·
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
 

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

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

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

... a set of square tooth pulleys scavenged from say an 86 charger that had a head from an 82 tc3 slaped on it 20 years ago and now installed on somthig like an 87 TII motor could cause some issues truing to center things up

there is I think a 6 degree difference in the old pulleys -I remember because the 314 cams I bought don't center with either pulley set - the cam centers at the middle of those 6 degrees

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

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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 ?
 

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The OP is correct in that there are some issues with our knowledge of the oem cams.
I've brought this up on occasion, but it's never gone very far.

1st Issue) Definitive cam gear geometry. I personally believe that there is no difference between late slider and roller cam sprockets, there was a different sprocket for the carbed H.O. car, other than that it is unknown. Many people will tell you there is a 4' difference in the sprocket however this does not work out mathematically with the given LSA's of the cams.

2nd) Cam durations, I've brought this up a number of times as well. Mopar advertised their cams duration @ 0.02" lift. Since 99% of cams are described with lift @ 0" or 0.05". This makes comparing very difficult. I can guarantee you that a mild roller cam with an advertised duration of 228' DOES NOT produce a HP peak @ 5500rpm, try 3500rpm. There is clearly more duration there than advertised. Even if the cam had an aggressive profile (ramp rate) and a butt-load of dwell over the nose it still could not make the power band we see on 2.2/2.5's. There is something missing there...
 

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Discussion Starter · #6 ·
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.
 

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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 ?
sooo according to ddg there's 2 late square tooth , 2 round tooth and 2 more for the tall deck

so , how'd they turn a cam in 82-3 with no pulleys ??
 

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Discussion Starter · #8 ·
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?
 
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