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“Name that engine” competition at the end, with fabulous prizes!)
I’m excited. Can you tell? Every time someone mentions even the faintest possibility of fitting an OHV top-end onto a Chief or a Scout, I go weak at the knees, and my jaw starts flapping with directives about “do it this way!”, or “make it that way!”. Which is easy for me to say, when I’m not the one making it.
So this time I’ll just shuddup and let some pictures do the talking. These pix are intended to give a bit of historical context to Indian OHV conversions. Except that I’m no historian – I’m simply gazing at these pictures like a palaeontologist who looks at old bones and thinks “Well, these two come from the same Family” or “This one must have evolved from that one”. If you want historical accuracy, go and read Sucher’s book.
By way of background, I should mention that there’s at least three, maybe four, different initiatives that could be going on to make an overhead valve conversion for Indian Chiefs and/or Scouts.
There’s one on the market already, made by Peter Arundel and others in Australia and sold through Starklite. These imitate the look of the stock side-valve Chief top-end, so concept-wise are a bit of an apology for OHV though they reportedly work well enough.
Now Rocky is at an advanced stage of reproducing Koslo twin-port OHV heads, that were originally an aftermarket item for hillclimbers during the ‘20s (see Rocky’s article last month in VI magazine).
Next, Rick Abbott has been wondering aloud about the possibility of casting up reproductions of the Crocker speedway heads made during the ‘20s and ‘30s for fitment to 101 Scouts.
Lastly, Lyle has the germ of an idea for something high-perf and twin-carbed, inspired by Harley XR heads.
Some of these projects involve exact reproduction, so no new design work is needed, but some may need modification to make them more streetable (for example, more generous finning) while others seem to be starting with a clean sheet of paper and can go to wherever inspiration takes them.
From an engineering point of view, it is relatively easy to make an OHV top-end that will give satisfactory results, because the design principles have been well established these last 70 years. What is not so easy is to make a top-end that is attractive, and stirs up lust in our hearts. This is in the realm of art, not science. I’ve said before that my own criteria for wanting a particular bike has always been based upon looks and sound, not on strictly engineering criteria which I regard as a “given”. In this regard, an OHV top-end design for an Indian can either be a work of art, or it can be a clunker.
If anyone out there is looking for inspiration, to prevent their doubtless well-engineered OHV design from becoming a “clunker”, then read on …
First up, lets have a look at the heads that Al Crocker and Paul Bigsby made for 101 Scouts in the late ‘20s. The November issue of British rag “The Classic Motorcycle” has a feature on two bikes fitted with these heads – one is a speedway bike using a Rudge frame, and one is a streetable 101 Scout. The speedway and hillclimb pedigree of these two engines is evident in the almost complete lack of cylinder head finning – presumably they used cooler-running alcohol fuels and also needed to cut down on weight.
The article accompanying these pix unfortunately shows a typical Brit misunderstanding of pre-war American bikes. Firstly, the bikes are referred to as “Crockers” when in fact both bikes are only Crocker from cylinder base-flange up, the rest being 101 Scout (yellow bike) or 101 Scout/Rudge (red bike). Secondly, the author assumes that side-valve Indians are boring, and must be made OHV in order to be exciting – “the Crocker story shows how engineering skill can turn pretty ordinary grey porridge into something special”, he says. Well, only in England were sidevalve machines “grey porridge”! His article also confuses these OHV-conversion “Crockers” with the later “Crocker-from-the-ground-up” Crockers.
Still, it’s good to see some exposure of such rare American iron in a Brit magazine. And he comes up with some interesting tidbits of information. Like, the fellow that restored these bikes (for a Mr Corbin, of seat fame) is Mr Gwen Banquer of Florida, who’s already borrowed a set of Crocker heads and has cast up 10 sets (the lender wouldn’t allow more than 10 to be made) to be used for Scout conversions. He says that modifications to the 101 frame are necessary because of the extra height of these motors – the cases have to be lowered in the frame. This somewhat reduces the appeal of such conversions, he says, as 101 Scouts are “not exactly thick on the ground” and nowadays owners are loath to butcher them.
Builders of a Warpath Scout should have no such qualms though, and would get a stronger Sport Scout bottom end to boot. And the idea of OHV could well appeal to someone with an incomplete 101 basket who has to look around for new engine parts anyway.
As for the heads themselves, well, for a streetable bike I am put off by the lack of cylinder head finning, and by the square profile of the rocker brackets which to me look kinda clunky. Indian’s own 45-in. OHV looks much more handsome in this regard. Though this matters not a whit to anyone for whom exact reproduction of a famous model is the name of the game – they’ll want them done exactly the way they were done back then.
Next, here’s a picture of the bike that allegedly got the mainstream American factories all dabbling in OHV again (according to Alan Girdler) during a period in which, after earlier post-WWI OHV tryouts, sidevalve had pretty much become the US industry standard. This is the Excelsior 45-in. Super X inlet-over-exhaust model released in 1925, which established 45-in. capacity as a class (previously most US bikes were either 61-in. or 30.50-in.) and this led later to Class C racing. Excelsior apparently had both Indian and Harley scrambling to come up with a counter-punch. Charles Franklin prudently increased the 37-in. Scouts to 45-in. for the production side of things, but made doubly sure for competition purposes by creating a batch of OHV machines in 1926.
Indian’s OHV is somewhat better known than H-D’s, because even though only a handful were made they were apparently a force to be reckoned with in hillclimbing competition. The story of these engines are very scanty, and deserving of some in-depth research by J. Hatfield or other such motorcycle historians. At least one batch of 26 was made in the ‘20s, and possibly some more in the early ‘30s (a photo of a later engine appears in Jerry’s “Indian Photographic History” with caption “Scout overhead-valve, 1930-33”). Hatfield and Halberstadt’s “Indian Motorcycles” offers two versions of the tale, one is that 26 were made in 1926, the other is that they were made in dribs and drabs from 1926 to the early ‘30s.
I like the look of these engines, they’re kinda neat. They’ve got more in the way of cylinder-head finning, though its still obvious that they’re are intended to be alcohol-swilling monsters. I also like the shape of the rocker brackets – more pleasing to the eye than Crocker’s effort.
The same top-end was also used to add some
pep to the Prince singles, again as a limited edition released only to
favoured riders for competition.
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