[BMFH]

Hello All

Since you are going to remove the Head and Possibly replace the Exhaust Valves.

They Should be .850 thousandths of an inch, Plus or Minus .020 thousandths of an inch above the BARE AND CLEAN Mating Surface for the Cam Housing.

Since you will have the Head Off you need to check the Installed tip Height on ALL 12 OF THE VALVE TIPS, and Adjust them as Needed.

I use a Bridge with a Dial Indicator Installed thru it, I have a Gage Block that Measures .850 thousandths of an inch to Pre-Set the Proper Measurement for the Dial Indicator on a CLEAN AND FLAT SURFACE, then I set the Bridge and Dial Indicator on EACH VALVE TIP to record their Measurements, then, I can adjust each Valve tip Stick-up or Down as Needed, if it is too LOW you Might be able to Grind the Valve Seat and or Valve just a "SMALL AMOUNT" if it is "Close" to the Specified Measurement, If that will not work then you need to replace the Valve or Valves that Do Not Measure to the Proper Spec's. If the Valve tip is TOO High, then you need to trim the Valve TIP to bring it down the the Proper Spec's. Be careful, if trimming the Valve Tip, be aware of the Clearance between the Cam Follower and the Valve Spring Retainer.

THEY SHOULD NOT BE SO CLOSE THAT THEY WILL TOUCH EACH OTHER IN NORMAL OPERATION.

Also check the UNDER SIDE of the Cam Followers, the Contact area between the Follower and the Valve Tip WILL have Some Wear, but it Should Be Just a Slight Amount, If the Follower is really Worn it will effect the Cam and Follower Geometery and will not Contact the Cam Properly and will Effect the Lash Adjuster in it's total Extension to create ZERO LASH AT THE CAM Base Circle, the Follower ROCKS ON THE CAM IN ITS OPERATION,
The Lash Adjuster Compensates for this Wear.

If you are Trimming or Facing the tip of the Valve Stem, it needs to be Done on a Valve Grinding Machine so that it will be Soothe and Square to the Valve tip, You can Trim Very Small amounts of Metal Off the Valve tip to get into the Required Spec's, It will be a TRIAL AND FIT PROCESS, and Takes Careful Thought to do it RIGHT.

IF you have the Head OFF you might be WISE to Check the Valve Guides and Valve Seats, and do a Clean-Up on them, Re Seat them and Replace the Valve Stem Oil Seals, the old saying,

"AN OUNCE OF PREVENTION, SAVES A POUND OF CURE"

Tale Care,

Dusty