Valve overlap clearance ?

[koko64]

Interested to see your solution. Good luck.

[Speeddog]

Monsta may have solved the issue by this time, but I was doing some heads and took advantage of the situation to swap parts and take a few measurements.

'95 900SS V2 heads, stock size valves with minimum cut on valve seats and valves to freshen them up.

With the carbie cams (OHT, VHT) valve overlap clearance was 0.042".

With ST2 cams (OHZ, VHZ) valve overlap clearance was 0.033".

Fitting larger valves reduces that clearance by 0.017" for every 1mm increase in valve diameter.

So...... if you go +1mm on both valves, with ST2 cams, they'd just touch. 


Going from carbie to ST2 cams, the shimming had to change, thinner closers and thicker openers:

                  CLOSER   OPENER
INTAKE         -0.18      0.41   
EXHAUST      -0.23      1.35

<Caveat: The above numbers are influenced by the manufacturing tolerances of all of the parts, and I didn't fiddle the shimming down to the last thou. YMMV.>

[monsta]

thanks for that SD..   

I've done the heads, the valves got trimmed a bit more. I bought a decent magnifying glass and blued the seats so that I could see the sealing surface better then turned them down to that.
Ended up with about 0.8mm. I'm pretty sure that'll be ok.

the heads are still sitting on my bench! 
But I have a new job that'll give me a LOT more time at home.
Hope to get onto it this week or next if I dont let this    doesn't get in the way!   
Will be around 43 deg C (109 F) here for next few days! so wont be going out to the garage much.