Rocker shaft installation

[johnnn]

I have a contradiction in my Aero-Vee build. I think my Rocker Shafts are assembled incorrectly. The manual specifies the gap in the rocker blocks should face toward the pushrod side of the assembly. The rocker blocks can go on the rocker shaft mounting studs only one way. The top hole in the block is smaller than the bottom hole. I think I have to disassemble the rocker shaft and turn the blocks around. Am I right? Does it matter? John

[Rynoth]

From the manual:

"Note: Pre-assembled rocker assemblies often need to be disassembled for proper installation."

If it doesn't match the manual, I would redo them.

[GraemeSmith]

Manual is pretty specific about spacing the rockers and then shimming the whole assembly correctly so the tappets contact the valve stems so the valves rotate. I just did a head job which involved two new exhaust valves and that threw the geometry out enough when I put the rockers back on that I had to reshim. I assume you would have to take them apart and rebuild them for this reason alone.

[Area 51%]

I've got no less than 3 (make that 4 if you count the Aerovee assembly manual) repair manuals for the air-cooled VW engine. In every case, except for the Aerovee, it has the gap in the blocks installed toward the valves and not the pushrods. As delivered, the Empi rocker assemblies confirm this orientation.
Not sure why Sonex has the block turned around.

[Outlaw6]

I asked Sonex that very question, here's what Kerry said:
Hi Chris,

In practice, the direction of the gap doesn't matter. The belief behind installing it facing up is that it will “catch” the oil that is being tossed around inside the head.

Blue Skies....

Kerry


Sonex Aircraft Tech Support

[Outlaw6]

Here's where I'm stuck. I put on the new style EMPI heads from Sonex last year and set the rockers and shaft based on the Aerovee 2.1 Rev Q, which gave me one 0.032 shim under each rocker block. At 10 hours with the new heads I pulled the valve covers and rockers had no lash remaining, so I torqued the heads and adjusted the valves (0.008" Intake and .014"Exhaust for the turbo Aerovee) and flew another 12 but the average CHT seemed to be getting high so I figured I would check the valve adjustment and once again there was no lash remaining. This prompted me to start researching rocker valve geometry and the procedure is different than explained in the Aerovee manual. From what I've found the goal is to get the swivel pad adjuster screw parallel to the valve stem at half lift. Here I'm only referring what the rocker shaft block shims are for not the rocker shaft shim which are for adjusting the lateral placement of the swivel ball on the valve stem.
With the goal of getting the swivel ball adjuster screw parallel to the valve stem at half lift, I began the iterative process of adding shims and checking the resultant angle between the adjustment screw and valve stem at half lift and I finally get close to parallel with 0.152" of shim, that's two 0.06" shims and one 0.032" shim and probably need to add a 0.016" to it even closer to parallel. Comparing the adjustable pushrod to the old pushrods it looks like I'll need to remake another set of pushrods about 0.22" longer.
I don't know what the geometry was on the old heads, only that it was like the Aerovee manual and I only got 150 hours before the #3 exhaust valve wasn't seating well enough to pass a compression test. Disassembly showed that valve stem was galled pretty bad and the valve to seat mating surface was cupped and worn beyond regrinding them.

I don't know if the instructions in the manual were made for the old style heads where one or two shims and trying to match up the look in the "correct" picture gives near parallel or if Sonex has another reason for setting the geometry differently.

Anyone else run into this quandry?