Originally Posted by
smittythewelder
Steve, maybe I'm the one getting it wrong, but I believe that it was the 2-cylinder B deflector engine, which used individual iron cylinders, and a bolt-together crank, and that three of these 10 cubic inch cylinders were used in the deflector C engine, which also shared crankshaft and crankcase parts with the 20" B, but not the 15" A engine. The later loop-scavenged 2-cylinder FB and FC engines also had the bolt-together crank. Apologies if I have misunderstood you or just don't know enough about this Fifties stuff. Did that deflector C triple really put out 75hp?!! Amazing!
About the A motors that were built for so long (piston-port intake, later with added case-reeds), I have a block from one of the first 1957(?) versions (unhappily, someone cut it in half to make an M engine). Loop-scavenged, and it is approximately the same block as used until the mid-60s, but it lacks a boost port. The water-jacketing, if you can call it that, consists of holes drilled around the outsides of the cylinders; the holes do not connect with each other, and the water could not flow, but sort of shake in place!! I have to learn to post photos so y'all can see this thing! Surely this feature was quickly revised, and I've seen the next version of this block, which looks like any block from the next ten years; the water jacket is cast-in so that the water can actually flow around the cylinders, but there still is no boost port. These engines had the pork chop counterweights on the top and bottom crankshaft sections, and I think this feature lasted into the early 60s.
Somewhere in the early 60s, the 25mm slide-type Bing (and maybe some Amals??) carbs got reoriented from vertical to horizontal.
Around 1966(?), the gear driven Bosch magneto was replaced by a heavy but otherwise very good energy-transfer type of flywheel magneto. I saw one of these on an FC, so they might have come on FBs and FCs at that time, but I don't know. At least some of the A motors at this time came with 25mm Bing butterfly-valve carbs. These little Bings were also used on the new piston-port C and D four-cylinder Konigs, and Mikuni versions (license-built, one assumes) of this carb were later used on Yamato 80s and the first RB and RC Yamato fours. Also about this time, the A Konig cranks had full-circle throws which were also thinker than before, and the crankpins, where they pressed into the throws, were increased in diameter form 17mm to 18mm. This made it less likely that you'd break a crankpin (done that) and more likely that you crack the thinner edge of the hole the pin pressed into (done that).
I think it was 1968 when Konig brought out the aluminum block A. I've talked about this somewhere else; a can of worms that didn't last long, though it certainly could be made to work. Besides the new block, this engine had a new crankcase, which used long studs in the center section to affix it to the block, and this case was used from then on, I believe.
Was it 1970 or '71 when the last generation FA arrived here, with an iron block, and for a few years siamesed exhaust elbows and a single pipe. No change in the crank, I don't think.
Oh, I should have mentioned the progression of big-end rod bearings, which started with nice long rollers and steel retainers, then (maybe 1964) went to little stubby rollers with rounded ends riding in retainers of (we thought) "beer-can" aluminum. These were revised very slightly when the stubby little rollers were given just slightly more length by squaring up the rounded ends, the aluminum cages being broached with squared-up holes to accomodate them. After my short time fooling with this stuff, I understand that the last of the FAs went back to long rollers and steel retainers; true?
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