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I am probably going to cause some consternation here, but, all I am doing is conveying how I do this operation, nothing more. It WILL be long winded.
As everyone is aware, I am a big fixture, jig, holder and tool person, and, I make my own tools for most operations. One of the sets I have made over the years is jigs to add dowel pins to the base and head gasket areas of air cooled two strokes I work a lot on. These tools are not simple ones to make, and the average mechanic that doesn't have machine tools would have problems making them in their garage.
As we all know, the base and head interfaces on our engines aren't that accurate, once the head bolts are loosened, we can usually move the barrels and heads a lot, and they aren't guide pinned to each other, nor to the cases. So, I add dowel pins to keep 'em aligned, like a 4 stroke has.
The tools for the head to cylinder I made, and use, are double ended. A flat plate is in the middle, to fit up against the top of the cylinder on one side, head gasket face on the other, with one side for the head, locates through the spark plug hole center, the other side, an expanding centering ring to center on the bore, all different bore sizes for that engine family. So, one tool locates and guides both the head and cylinder for dowel pin holes.
I have over 25 sets of fixtures for all sorts of engine families. Decades of making these tools.
Another pair of tools sit on the base gasket surfaces, center up, and add the holes for the bases.
A bench hand punch, with interchangeable hole size anvils are used to trim the base and head gasket holes for the dowels.
I prefer a very thin hollow dowel around the stud/bolt, instead of a pin, just keeps it a lot easier.
The whole purpose of this stuff is to get and keep the various parts centered on each other, so things like the edges of squish bands align dead straight centered on the cylinders, and cylinders sit on the cases straight.
I have also faced the heads and cylinders, then cut the cylinder deck for a special O ring to replace the copper head gasket, works good, IF you get everything flat, square, and done right. For the O rings, I learned from a machinist that always came into RC Engineering, that had a business that cut a tapered O ring grooves, in pantogram, that angled out from the head surface, down into the ring hole, wider down in the hole than at the top. So when compression would hit the ring, it was pushed into an angle instead of a flat 90 degree wall of the groove. Helps to seal the junction immensely On these interfaces, no copper or other type of hard head gasket was used, just the O ring and squared head/cylinder surfaces.
Yes, a lot of work, but, could you imagine what chaos would occur if the cases weren't dowel pinned to each other, clutch cover not doweled to the case side, not good.
I also do a lot of tri-power, dual quad Pontiac/Corvette/Ford carb/manifold doweling. Those intake setups usually use an end set of carbs opened by hard linkages, with end carbs that MUST close all the way, and, if the carbs aren't dowel located, if one is taken off the manifold for any reason, when reinstalled, the linkage usualy has to be readjusted. With the dowels, once the carbs are tightened down, and the linkage is set correctly, it stays adjusted, even with he carbs taken off and put back on, because the carbs sit in the same place when they are reinstalled.
Like I said, lots and lots of work to do, but, that is the way I like to do things, fully located.
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