This is the start of timing the cam chest. The followers have to have clearance first ,for the higher lift cams. Then all the followers need to be shimmed.
The half time pinion on the crankshaft has 5 slots for timing. Each slot 1.5 deg different. this gear also comes in 10 different sizes. in 2 thou increments from -10 thou to + 10 thou. Why, I'm glad you asked. The idler is on a movable mount. At completion of assembly you need to have zero clearance on all the gears when cold. So start the cam gears on to the cams by 1/8th of an inch and ensure they are square. Fit both cams. Noting the cam gears aren't keyed. The idler gear has 15 deg between each tooth. install idler gear on mount and push it up into mesh. Ensuring the gears rotate freely but with out free play. Now that sounds easy right. Not so. As you tighten the 3 nuts on the idler pedestal it moves. Fast forward 2 hours. Now pick the correct half time pinion to match the the idler to have no clearance , yet free to turn. Another 2 hours on.
I won't bore you with the rest unless you need to know. But using the crank 1.5 deg slots and the 15 degrees from the cam idler lets you get the rear cam close. Then pressing on and of the cam wheel and using a dial gauge and degree wheel you set up the rear cylinder. Then add 50 degrees and another 360 degrees and you do the front cylinder. This time you cant use the crank pinions 1.5 degree slots for adjustment as you will alter the rear cylinder. Any way 40 hours later it should look like this.
