I'm getting ready to pull my K8 motor, after spending dozens of hours pouring over the Hondaman Bible, and wondering if the '69 - 76' kits will work in my '78 motor. If not, does anyone have an idea if/when the later model kits will be available? My thanks to everyone for this thread full of useful info!
Like ^^ they said, it will be fine in the K engine. It is actually OK in the F2/3 engine if you don't mind dropping the compression ratio a bit: the OEM in the F3, for example, was 9.2:1 CR, and if you mill 0.040" (1mm) from the head with the 836 CI pistons, it comes in at 9.02:1, which is about where the K0-K6 engines are, stock.
If you use the DOHC750 pistons (1979-1982) with the shoulders trimmed down 1.5mm, for 12mm in from the outer edge (w/o milling the head), it comes in at about 9.2:1 CR at 760cc. This works fine, too. If you use these pistons in the K7-8 engine, the CR is about 9.8:1, requiring premium-fuel--only operation. On these, I have added some extra quench band width and done other things, like trimming back the chamber near the valves to improve flow anyway, to augment the chambers a little bit. This ends up requiring you "CC" the chambers afterward to make sure they are close in size to each other, though, a messy thing to have to do...
