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I think we can assume that the original engine designers wouldn't have got to the bother and extra cost of the cutouts if they weren't needed.
The trouble with that assumption is it ignores what drove the designers of the engine at Coventry Climax. It's said they and the BLMC team that got them involved (Spen King, et al) were primarily interested in the 16-valve version of the slant-4 engine for competition, presumably for the Dolomite Sprint as a Group-1 race car, though possibly with an eye on Groups 2 and 4. And the restrictions and allowed modifications for those homologation groups may mean they designed in aspects that were only significant to the engine at the limit of tune the groups allowed.
I'm sure I've read the Group-1 engines ran to something like 175 bhp on a standard spec engine (at least to the tolerances the FIA's CSI allowed in 1973) and SU6s. On better carbs it could come close to what the far more specialized 2L Cosworth BDG engine gave. It's true that Group 2 and 4 engines could have used mods allowed under the 100-off rule from Appendix J to 1975 - that allowed alternative cylinder heads and transmissions just on production of 100 kits of parts to buy. But while that may have allowed alternative cams and other mods to the head they could do 100 fold, it doesn't appear to have allowed alternative pistons. So I assume even the Group 2 and 4 engines were using the pistons visually indistinguishable from the Mahle piston (homologated as evolution 3 in April 1975) in CSI inspections or CSI instructed scrutineering, like happened to DTV [Dealer Team Vauxhall] in Portugal 1978.
Yes, I know about the arguments that BLMC was short of cash in the early 70's. But that involved going so far bust by 1975 that the Ryder Plan reckoned it needed nearly £3 billion to dig BL out of the wreckage BLMC had become - something like £20-25 billion at today's values. And the leeway in that amount of misspending would make any, possibly all, of us rich.
And at only 5000 units a year maximum, the production of the Sprint engine would have been so far down the balance sheet, the production cost chasers wouldn't have noticed it. If you don't know about the work of production cost chasers in large Co.s like BLMC, you've probably never died of boredom.
Also, there was the supposedly significantly expensive cost reduction programme in the early-mid 70s (apparently ended in 1975 with the Ryder Plan), intended to make the 16-valve slant-4 suitable for mass production so SD2 could break into the US market (and separate from the the programme to meet emissions legislation from 1976). I think that must show that the engine really wasn't initially designed with large scale mass production in mind. You might feel qualified to say that's down to bad design. But I don't feel able to criticise Lewis Dawtrey and Harry Webster's, Harry Mundy's, and Spen King's design teams in that way.
Graham
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