I must confess that i had not seen, or read, this very interesting article before. The combustion chamber shape bears a strange resemblance to the Polysphere chamber, sometimes called the "Semi Hemi", of about 1955, but of course, it's not identical. Quite similar in my view,.. but not identical.
The constant use of the word "hemi" in this article is not warranted, or justified & belittles the project unjustly by making it sound like there is a measure of "penis envy". If it truly is a better design, then it will stand alone with a name of it's own.

It looks like someone has taken the better mousetrap & done all in his power to make it even better still. The hemi chamber was actually in production in '51, so it has taken over 50 years for a serious attemt to improve it to take place. I wish him every success.

I was unaware that the BBC was still in production. I had believed that Gov't mandated fuel mileage rerquirements had killed all the big engines. It's a well designed pushrod engine with a good reputation that has always lived in the shadow of the long discontinued 426 Hemi, but it certainly outlived it in production.

I was also of the [mistaken] belief that the SBC had been replaced by the Gen III. I doubt that the SB2 will directly bolt into 1955 & '56 cars due to a diferent fromt mount, but thats nit picking, & i adjusted your 1952 date up to 1955 as i really start counting from date of actual manufacture. Chryslers experiments with their design date to the early forties with their 12 & 16 cylinder aircraft engines. Lets just stick with the first production year for simplicity.

Continuous production for 50 years, well, i guess that these are some of the "very few" that i refered to earlier.
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A15 DATSUN______A15 DATSUN______A15 DATSUN

But the subject of this thread was the A15, & this wonderfull engine, sadly no longer produced in this version, has the potential to comfortably haul around the heavier, small model Datsun bodies by virtue of its 82mm stroke, but is generally not regarded as a desirable swap in place of an L series engine, which is where this thread started.
A better plan, when we remember that the 140J was built for the larger L series, is to go for the L18 as this seems to be the version that responds best to performance improvements, is still both readily & cheaply available, & is a direct bolt in. The shorter stroke [than the L20b] allows a free reving engine & the lower height [than the L20b] will minimise any clearance issues, so thats my suggestion & recomendation for this car, with the L20b as the alternate.