Glenn M

I have Porken's CAM timing tool and need the timing specs. for an 88. The WSM says 1.8 +- 0.1 mm for cyl 1-4 and 2.0+- 0.1mm for cyl 5-8. What is this value in cam degrees or crank degrees. I'm missing something.

Thanks.

Jim_H

Those numbers are for indexing the cams themselves with a dial indicator. Totally seperate from what Ken's tool is used for.

Glenn M

With the cam tool I measured 2 cam degrees on the right cam and three cam degrees on the left cam. How does this compare to others? I

Thanks

Jim_H

To the right or left of the 'V' ??

Glenn M

Advanced, to the left.

PorKen

Glenn,

I missed this thread. What did you end up doing?

Peter F

I tried to measure the PS side on my 90 GT yesterday.
Got 2 holes to the left of center point, almost spot in the center of the V behind the cam gear.
That would be 2 cam degrees advanced right?
Not sure if that is normal from Factory or if someone has set it to advanced?
Will try and measure DS side tonight and see what I get.
I have not adjusted my cams so I will not make any changes at this point.

Cheers/Peter

Glenn M

I set mine to 0 degrees.

Glenn

docmirror

Glenn,

I don't have the WSM manual in front of me right now, but those numbers typically refer to the depression on a lifter using a dial gauge. That's why it's in mm not degrees. This is called "degree-ing" the cam or "indexing". The measurement is taken from the lifter, where the lobe actuates because there is slight differences in the lobes once the cams are ground. The tool you have only measures the location of the bolt holes in the flange of the cam. It is useful only to maintain a repeatable location of the cam index once the pullies or belt have been moved. It is not (I don't think) intended to replace the indexing of the cams on reassembly.

To perform a correct timing of the cams requires removal of the cam cover, and a dial indicator with plunging point. One of the lifters is used as a reference, and a certain amount of depression of the lifter by the cam lobe is used to define the relationship of the cam angle to the crank angle. The cam is set at this depression, the cam(s) are then locked in place using a matchbook cover under the cam journal. The engine is then set at 0TDC using the dial gauge, and the pullies and belt are assembled, and the slack is taken up. Then remove the cam locks from under the journal, rotate around twice and recheck the TDC, then the lifter depression.

PorKen

Peter,

Correct, using the 'ZVA': left (CCW) is advance, right (CW) is retard; the opposite of the crank balancer or ignition advance.
...

Technically, the tool's reference is the center of the camshaft woodruff key, via the cam gear hub. This is a static measurement.

Ideally, the user would determine each cams' degree measurement using my tool and the WSM dial indicator method to determine any tolerances. From that point, the cams can be reset to that degree measurement, for example, after changing a cam gear.

Because the measurement using the dial indicator is done on the intake cam (which is driven by a chain from the exhaust cam), operator error, chain slop, valve train wear, etc. can affect the reading given. The most accurate method would be to use a degree wheel and determine the opening and closing points of the cam, and set accordingly. People using this method, often measure off of an exhaust cam lifter, because of the reduced error threshold.

My tool reads off of the exhaust cam, so is more repeatable for the average user.

At some point in the future I hope to have a table (like the WSM cam tables, pages 15-121, 15-140) which shows the degree measurement by engine, and the percentage of variance, if any. But I will need more than one data point to do this (Jim_H 's GT is 1 degree advanced ).