A couple more hours of concentrated effort got the engine together. This was only moderately traumatic as I only lost two intake trumpets, and both reappeared eventually.
Looking at the various cam covers and whatnot, it looks more likely that the engine is in fact a pair of flat eights, not a set of four flat fours I as surmised earlier; the cam drives all appear to be at the front of the engine. Wikipedia supports this, saying it was a development of the 1.5 litre V8 used in the previous formula.
The zoomed in photo above shows detail that is hard to see, even with the 4X glass: the little BRM badge on the upper exhaust cam cover, the lumpy black injection system between the intake trumpets and driven by a belt off an intake cam, the equally lumpy aluminum water pump driven off the lower exhaust cam. As models go it is very nice but zooming in too far can show a lot of microscopic flaws. (Picture taken with the macro setting on my little point-and-shoot Canon).
Overall, Wikipedia doesn't have much good to say about the motor; it was heavy, complicated and unreliable, and Jim Clark managed the only win with it, in a Lotus at Watkins Glen in 1966. Lotus wisely moved to the Cosworth DFV in 1967, leaving BRM to soldier on with the H16. By 1968 even BRM had given up and had switched to a V12, not that this improved things. Still it's a lovely little oddball.
Overall the kit will be only just over 90 mm in length. As with many kits, it's too bad that much of the motor will be obscured once it is all assembled and ready to display.
I'll be busy with other things for a few days, so no further progress is likely until mid-week. Next will be rear suspension and those lovely exhaust headers. Stay tuned!