I highly recommend this upgrade. If you look at the stock setup of rockers with the clips, you will find this was adequate back in the 70’s, when the speed limits were lower and the fuels were better. Nowadays it’s common for Thing owners to be doing 65-75 mph on modern highways.
That’s especially true out here in the western states where it can be a far piece to the next town, even on state roads. For modern application of your Thing, and for long distance touring trips, it’s a good idea to go to solid rocker arm shafts.For those who know me, I am all for keeping our Things as stock as possible. My exceptions have always been for upgrades that enhance safety or performance, without compromising longevity. Solid rocker arm shafts have proven themselves on many of our yearly rallies and in day-to-day service.
To better understand my point, if you look at Figure 1 you will see the stock set up with the spring clips on each end of the rocker arm shaft.
These can, and at times do come off under higher sustained speed conditions.
The clips get hot, and then pop off the end of the rocker arm shaft. This allows the rocker arm itself to move down the shaft and start really messing up your engines internals, and your wallet.
The arm can’t come off the shaft, but it does move off of the valve stem, and allows it to commence beating itself to death. Sometimes it allows the valve stem keepers to come out, and the valve to drop into the cylinder. Sounds like the pistons are swapping holes back there, and the engine runs very rough, because you got one valve trying its best to go somewhere more comfortable. That is NOT fun 1,200 miles from home, or just outside of Elephant Breath, Idaho.
Figure 3 shows the difference between the stock shafts and the newer solid shafts. The two primary differences are evident in the larger diameter center portion of the solid shaft and the fact the ends are bolted on to the shaft, thus replacing the clips.
The new solid shafts can be ordered from Cip1, or Moore Parts Source. They usually run about $50.00 a set. You can install these yourself, and you can do it without pulling the engine. The shafts come with everything you need to do the job, and you won’t be sorry you installed them. They do run quieter and they do the job.
Set up of Solid Shafts
The new solids come with the shafts, end bolts, and shims.
The shims are two thicknesses, about .10 and .30 thousands. These are used on the shaft for two main functions: first, to take slop out of the spacing between the rockers and the rocker arm perches; second, to set the rockers up so the valve adjuster contacts the valve stem .10 thousands off center so the valve will rotate.
This shows the exhaust rocker on the left correctly set up so the adjuster makes contact .10 thousands off center, while the intake valve on the right is incorrectly set up dead center of the valve stem. You set the adjuster .10 off center to enable the valve to rotate, and that reduces the chance of a valve burning if a piece of carbon gets in there and sticks to the seat. You get this spacing by inserting different thickness shims in between the rockers and the center machined area of the shaft or between the rocker arm shaft perches. The slot in the perch IS ALWAYS installed up
You will assemble the shafts a couple of times using different combinations of shims to get the desired offset on the valve, and the best tightness on the shaft itself so the arms don’t have excessive play from side to side. Feel free to use shims from the old shafts if you need them to set up properly. Just clean them before use. I use a new cylinder head to do the set up on the bench, but it can be done while the engine is in the Thing, it just takes longer.
After you get the shafts set up the way you want, disassemble them and coat them lightly with wheel bearing grease, or oil. I use the wheel bearing grease if the engine is going to sit around the shop for a while before installation.
If you have any questions about setup or installation, you can contact me through my web site at www.vwthing.us.