TOPIC:

The base circle on all stock cams is the same.
The wider measurements you are encountering are the quietening ramps.
This is why you should take clearance measurements with the lobe pointing directly away ( 180 degrees )  from the shim to ensure you are fully on the base circle and not on the ramp.
Especially with higher lift / performance profiles.
You should also note that the upper clearance spec for the unitrack cams is 0.18mm so aim for that when shimming.

Thank you zed1015 for sharing that tasty morsel of knowledge.
Your fine comments bring much needed clarity to my blurry visualizations, and greatly enhance my forum participation experience.

zed1015 wrote:

The base circle on all stock cams is the same.
The wider measurements you are encountering are the quietening ramps.
This is why you should take clearance measurements with the lobe pointing directly away ( 180 degrees )  from the shim to ensure you are fully on the base circle and not on the ramp.
Especially with higher lift / performance profiles.
You should also note that the upper clearance spec for the unitrack cams is 0.18mm so aim for that when shimming.
 

Makes sense that the best lobe-shim engagement spot would be immediately past the quietening ramp, and no distance before or some point further down the lobe surface. 

Schumann was provided lash measurements of the head with it's standard-lift stock cams, along with valve tipping adjustments needed so I could utilize 2.50 shims throughout. 
Subsequently I purchased the set of Unitrak cams, and that list was revised to favor my wrong interpretation of the base circle measurement (being 0.10mm bigger) duh!  My request was that 0.05mm additional tip material be removed to maintain my shim preference.

If the lash ends up 0.15mm +/- then I will be a very happy man.





 

Might it of been an idea to send your head man the cams (or is he too far away 

The polished up ZN buckets will be reused in their original locations.

 

Wookie58 wrote:

Might it of been an idea to send your head man the cams (or is he too far away 

 

Chris Schumann heads are shipped with no cams, caps, or shim buckets.  He said those are not needed for his rebuild process, which maintain tip heights unless otherwise requested...

I thought that was "different" at first.  The program works...and it reduces the shipping costs as well. 

BIG Win-Wins! in my FSM...

daveo wrote:

 

Chris Schumann heads are shipped with no cams, caps, or shim buckets.  He said those are not needed for his rebuild process, which maintain tip heights unless otherwise requested...

I thought that was "different" at first.  The program works...and it reduces the shipping costs as well. 

BIG Win-Wins! in my FSM...

No need for the buckets and cams etc when doing a valve job.
Just aim to get as close as possible to 37.2mm on the stem heights to get in the upper end of the shim range.

daveo wrote:

The base circle and the measurable diameter of this 300° duration camshaft lobe are not one and the same.

The drawn lines show where the true base circle to lobe transition points are

 

Please consider the above information and dimensions below to be revised and corrected...

Checking out the head work...

Yup it's that close. 
Steve

Very close!




Out with old...







Done with that!

daveo wrote:

Done with that!

 

So I thought...Those two inserts were flush with the head surface, and that was no good. 



See: kzrider.com/forum/2-engine/620085-stripp...mesert-repair#897212


Fixed that, and cleaned things up: