TOPIC:

I have put the engine together now with GPZ pistons and a 0,7mm shaved KZ750 head. I still have very good piston to valve clearance. Even with the GPZ 83-85 cams set at 105 degrees.
I found a couple of GPZ 83-85 cams on Ebay that I’m planning on grinding.
Talked to a couple of companies that can grind the cams without welding. Maybe take 0,5mm of the backside.
Hopefully the hardening will be deeper then that.
As I understand the intake and exhaust cams have the same lift and duration but the exhaust has smaller diameter to compensate for the lower valve seat in GPZ heads.
So im thinking about using an intake cam for exhaust to avoid having very thick shims.
Right now I have 2,85mm shims for some exhaust valves with a standard GPZ 83-85 exhaust cam.

It says here that these cams with 9,27mm lift don’t require racing valve springs.
www.bikeside.de/Racing-camshafts-STAGE-1...7mm-control-time-283.

If I take 0,5mm of the back of a GPZ cam the lift will be 9,492 based on info I found here in the forum.
Maybe that’s risky with stock valve springs?

Sixten wrote:

It says here that these cams with 9,27mm lift don’t require racing valve springs.
www.bikeside.de/Racing-camshafts-STAGE-1...7mm-control-time-283.

If I take 0,5mm of the back of a GPZ cam the lift will be 9,492 based on info I found here in the forum.
Maybe that’s risky with stock valve springs?
 

Stock springs that have been installed for 40 years will be making about 60 PSI on a valve spring checker at installed height (usually not enough to seal)
To seal your valves and get repeatable high RPM without float use aftermarket springs. APE springs out of the box give 80-90 PSI installed seat pressure and they are not a lot of $$

 

If you take that much off the back of the cams "can you get shims thick enough?" And if so will they stay seated in the buckets at high RPM ? With regards the hardening, I don't believe the stock hardening goes to that depth (one for the engineers out there) so I would think they would need re-hardening and polishing, repeating the hardening process may make them brittle !! (I've watched "forged in fire"  )

Thanks for the advice on APE springs. 

Shims will increase from ~2.25 to 2,75 so it’s ok.
It will be a test of how deep the original hardening goes.