ATR Hydraulic Roller Camshaft - Degree Measurements

[Spooling]

I degreed in my camshaft today. It is an old ATR 214/210 Billett Hydraulic Roller. Using the Rollmaster Timing Chain Set – certainly made changes rather easy.
The Cam Card defines Maximum Lift at 104* ATDC

I collected the following data:
--------------------------------------
At 2A (2* Advanced) on the crank gear - I measured (91+124)/2 = 107.5* ---> 3.5* Retarded
At 4A (4* Advanced) on the crank gear – I measured (88 + 123)/2 = 105.5* ---> 1.5* Retarded
At 6A (6* Advanced) on the crank gear – I measured (49 + 158)/2 = 103.5* ---> 0.5* Advanced
-------------------------------------
Last time I degreed in this camshaft back in ~ 2001 - I got pretty much the same numbers – well at 6A on the crank gear I measured 104* which is "dead nutts" (not retarded or advanced).

The timing chain set certainly corresponds to a 2* change per each tooth moved, yet I am curious why - if I was to install this assembly “straight-up” – it would be ~ 5.5* retarded?

 

[Spooling]

Is it possible that I am doing something wrong - I mean with this keyed crank gear, moving the gear with relation to the camshaft position really does not change the cam/crank alignment with reference to the key-way on the crank gear.

By this, I mean with the cam gear mark at exactly 6:00 position, the crank key-way is at ~ 2:00 position, and by me moving the keyway on the crank to another position - namely from 4* to 6* does not change the position of the crankshaft with relation to the camshaft - yet my numbers I collected changed by 2*

Reference the attached pic:

 

[turbo nasty]

How did you verify TDC and zero your pointer? Heads on or off?

 

[Spooling]

Heads off. I used the piston stop technique and divided my numbers obtained by the degree wheel by 2. I was pretty close everytime I did it by eye, only off by a couple degrees eyeballing it - yet I set it "dead nutts" each time - using the degree wheel.

Thanks for your assistance.

 

[turbo nasty]

Confused you used a stop acroos the bore and did forward and reverse and split the two or "eyeballed it" ?

 

[Spooling]

"eyeballed it" ?

No-No-No.

I "eyeballed" where I thought true TDC was, set my degree wheel at 0* and rotated the engine to installed my piston stop protruding into the bore of cylinder # 1. T then went one way, recorded that number and back around teh other way, and recorded that number and "split the difference" - then found TRUE TDC based on the measurements obtained off of the degree wheen, and in comparision to my initial assumption (eyeballed) - I was only off by a couple of degrees - so my eyeball method was "close" - yet I used TRUE TDC obtained using the degree wheel.

Upon re-examining what I did today - by looking over the pics, I see that each adjustment I made, I simply moved the crank gear CCW to obtain another 2* of advance. Yet in doing this, the "clocking" of the keyway remains in the exact same position as the camshaft position - so what is really changing? I don't think anything - with relation to TDC and the position of the camshaft and the crankshaft keyway.

Appreciate all input, and I am probably gonna have some free time over the weekend to see if my assumptions are correct.

 

[bison]

You have to pick your initial install point and use the intake centerline method when degreeing as you explained. You will see variations in lift and duration on the card compared to reality since the lobes are generally meant to be ground on larger cores. The result is a shrunken lobe and valve events that don't match the card. also the card assumes a symmetrical lobe and they are not. Knowing where you want the ex closing @.050 or the intake opening at .050, etc will let you know if you need to advance the cam or not.

 

[turbo nasty]

Bisons makes good points as most cams are skewed slightly from what the card shows.
For example when I was degreeing my cam in I noticed that the exh didnt close all the way and stayed off the seat about .005 or so into the intake event for scavegening effect. Cam card didnt show it staying open slightly.

 

[bison]

Bisons makes good points as most cams are skewed slightly from what the card shows.
For example when I was degreeing my cam in I noticed that the exh didnt close all the way and stayed off the seat about .005 or so into the intake event for scavegening effect. Cam card didnt show it staying open slightly.

There are a lot of things that cause the variation. It's not for scavenging either since once the piston is at and beyond tdc there is no ex scavenging. The back pressure is higher than intake pressure so when the intake valve opens
the flow is in reverse near tdc and has the same effect as reducing the intake duration and diluting the intake stroke with inert gas. The valve timing events are all a compromise. A better compromise can be achieved with some careful analysis and experience.

 

[turbobitt]

I degreed in my camshaft today. It is an old ATR 214/210 Billett Hydraulic Roller. Using the Rollmaster Timing Chain Set – certainly made changes rather easy.
The Cam Card defines Maximum Lift at 104* ATDC

I collected the following data:
--------------------------------------
At 2A (2* Advanced) on the crank gear - I measured (91+124)/2 = 107.5* ---> 3.5* Retarded
At 4A (4* Advanced) on the crank gear – I measured (88 + 123)/2 = 105.5* ---> 1.5* Retarded
At 6A (6* Advanced) on the crank gear – I measured (49 + 158)/2 = 103.5* ---> 0.5* Advanced
-------------------------------------
Last time I degreed in this camshaft back in ~ 2001 - I got pretty much the same numbers – well at 6A on the crank gear I measured 104* which is "dead nutts" (not retarded or advanced).

The timing chain set certainly corresponds to a 2* change per each tooth moved, yet I am curious why - if I was to install this assembly “straight-up” – it would be ~ 5.5* retarded?

I wonder how much one cam tooth throws off the measurment. Did you try the "Straight-up" measurment and move the cam gear over one tooth ? It's been a while since I messed with a chain so don't have a feel for how much change one tooth movement will give.
Allan G.

 

[Spooling]

I should have some free time over the weekend - and I plan to do a better analysis.

I been thinking about what I wrote earlier, and I understand the logic behind the Rollmaster with the various keyways on teh crank gear, and how they all effect my readings by 2* per change - exactly like the gear is stamped.

I believe that the slots machined in the crank gear - with relation to the centerline are at ALL different angles.

For example, with the crank gear set at 2*A and it's mark lined-up with the cam gear - if you were to draw a verticle line and another line from the center point - to where the crank keyway is - and measure with a protractor - you would get ... say 37* (hypothetical).

Repeat again at 4*A and you sould measure ... say 39* (hypothetical).

Repeat again at 6*A and you sould measure ... say 41* (hypothetical).

All along, I was thinking I was doing something wrong - yet such is not teh case.

Again - Thanks guys for offering your viewpoints.

 

[fastblackracing]

You are onto it now. What happens is the crank gear key stays in the same place but the camshaft gear rotates clockwise ever so slightly for each 2 degree advance change you make. If you look at the crank gear key slot relative to the tooth above it, it moves a bit with each 2 degree change. Look at the -8 degree slot to tooth position and compare to the +8 degree slot to tooth position and you can see the difference. The cams almost never measure exactly duration to cam card numbers and that is why you should use the Intake centerline method. It is common from my experiences for the cam to be off between 2 and 10 degrees on the intake center line. the duration is usually within 4 degrees. I like to write down the lobe lift on a line at [BTDC] 10*,8*,6*,4*,2*,0, intake and exhaust, this will show intake valve opening vs. exhaust valve closing lift giving you a better idea of what is happening at tdc crossover period.

 

[fastblackracing]

there is no need to concern yourself with what key slot you end up using as long as you get the intake center line where you want it. Does your cam card state what what the lobe centers or lobe separation angle is? This is a seperate number from the intake center line.

 

[Spooling]

It is common from my experiences for the cam to be off between 2 and 10 degrees on the intake center line.

Wow - that really is quite a large amount of variability !!!

I am set at 6A now (6* Advanced) and I measure 103.5* which correlates to 0.5* Advanced. Think I should add 2 more degrees of advance for a total advance = 2.5*?

I am gonna measure over the weekend:

1. Setting straight-up at dot-to-dot (assuming measured results will be = 5.5* retarded)
2. Setting at 8A (8* Advanced) (assuming measured results will be = 2.5* Advanced)

This is based on each movement or change increment on the Rollmaster Crank Sproket correlates to a 2* change.

Lastly - "Many Thanks" for sharing your experience with me !!!

 

[Spooling]

Forgot the cam card:

 

[fastblackracing]

ok your lobe separation angle is 109* what does your intake center line check at right now is it 103.5?

 

[87GN_70GS]

I wonder how much one cam tooth throws off the measurment. Did you try the "Straight-up" measurment and move the cam gear over one tooth ? It's been a while since I messed with a chain so don't have a feel for how much change one tooth movement will give.
Allan G.

It would be : [1 cam tooth/(total # of cam teeth)] x 180 deg

(it's not "x 360" cuz the cam moves at half the crank)

 

[87GN_70GS]

It looks like at 103.5 ICL, the cam is 5.5 deg advanced. I would leave it there.

 

[fastblackracing]

It would be : [1 cam tooth/(total # of cam teeth)] x 180 deg

(it's not "x 360" cuz the cam moves at half the crank)

But 4 cam degrees=8 crank degrees and we measure/degree in crank degrees. If the cam gear has 40 teeth and I move it 40 teeth it is right back were we started 360* not 180*

 

[fastblackracing]

Spooling if your cam is at 103.5 ICL leave it there or move it back to 107.5 ICL you do not need to advance it any further.