1973 Z1 Maui

Went through all the bearing locations one at a time with the other end supported by a lower half shell. I learned that three locations were pinching the split. Two on intake, one on exhaust. I lightly eased the very edges of the split on the caps and head, just like removing an edge burr. This fixed the problem, cams move easily now when fully assembled. 
this begs the question, why now?

My guess, the new bearing shells were not perfect, never seen this problem, I always check the cam spins free.
Newest project, camshafts and two bearing caps missing.

 

Obviously checking cam clearance with measuring tools and plastigauge is a must but I wonder about one thing. Aside from my specific problem I’ve suffered, let’s say you have good condition cams and new stock bearings. What if the clearance is somehow out of spec? I don’t think there are over or under size bearings available.
I’m going to replace these bearing shells and get a set of cams and I’ll of course do all the checks, hopefully the numbers come out ok.

I guess with no other size bearings available you would have to remove a little material from the back of the bearing (the coating isn't thick enough to risk scraping the face - how it was done a very long time ago) to relieve tightness. don't know how you could reduce clearance for a loose fit without a big spend (build the cam up with hard weld and regrind to spec)

If you checked the cams, why are you going to replace them?  Were they damaged when the bearings turned?

There were a few spots that are damaged, I don’t think I should use them. They do measure near the top of the tolerance, if I could find a shop that could resurface them and stay above the minimum they are usable. I imagine it would require some pretty nice grinding equipment, there is only one machine shop here, I may ask them.

I’m thinking an 8 or a 16 finish. Going down to a 4 might be too good and not pick up enough oil

wrote:

 
it has heavy duty studs but I don’t see how that could cause this, there are a lot of hot rod Z1s out there running HD studs.



 

Hopefully you have found the cause of your issues but i just spotted this statment i missed which you may want to check up on..
The stud holes in the barrel casting taper in towards the center from each end leaving a raised casting flash midway down..
In some cases there is quite a restriction in that area when fitting the larger diameter HD studs that can severely restrict oil flow to the cams and has been known to cause cam and cam bearing damage.
I always bore the four outer holes straight through with a 12mm drill to ensure sufficient clearance and oil flow.
You don't get this issue with the stock stud due to their reduced shank diameter ..

 

wrote:

wrote:

 
it has heavy duty studs but I don’t see how that could cause this, there are a lot of hot rod Z1s out there running HD studs.




 

Hopefully you have found the cause of your issues but i just spotted this statment i missed which you may want to check up on..
The stud holes in the barrel casting taper in towards the center from each end leaving a raised casting flash midway down..
In some cases there is quite a restriction in that area when fitting the larger diameter HD studs that can severely restrict oil flow to the cams and has been known to cause cam and cam bearing damage.
I always bore the four outer holes straight through with a 12mm drill to ensure sufficient clearance and oil flow.
You don't get this issue with the stock stud due to their reduced shank diameter ..

Zed1015 is this still relevant to the later “J” motor 

wrote:

wrote:

wrote:

 
it has heavy duty studs but I don’t see how that could cause this, there are a lot of hot rod Z1s out there running HD studs.





 

Hopefully you have found the cause of your issues but i just spotted this statment i missed which you may want to check up on..
The stud holes in the barrel casting taper in towards the center from each end leaving a raised casting flash midway down..
In some cases there is quite a restriction in that area when fitting the larger diameter HD studs that can severely restrict oil flow to the cams and has been known to cause cam and cam bearing damage.
I always bore the four outer holes straight through with a 12mm drill to ensure sufficient clearance and oil flow.
You don't get this issue with the stock stud due to their reduced shank diameter ..

Zed1015 is this still relevant to the later “J” motor 

Yes! It's relevent to them all and worth checking.
It's just a result of the way the stud holes in the blocks are cast and they don't drill them through.
It's not an issue with stock stud because even if the 10mm threaded end only just slips through there'll be enough clearance around the reduced shank.
With the HD studs the diameter is the same all the way down so that's where the tapered casting can cause problems.

 

Thanks for the info Zed, I never heard of this before you clued us in on it.

Rick H.

Thank you, that is a great tip, I will surely do this, still waiting on some parts to assemble the top end.

Howdy, now I can comment, have been lurking and following your build - keep it up !