View Full Version : Q. about Yamatos, AND a thread for old-timers.

03-05-2015, 09:53 AM
First, somebody here has this info in their head:

I have some old Yamato 4-cyl stuff from the earliest piston-ported days of the mid-late Seventies. These are what I refer to as "3-port" motors, meaning about 1970-style with two transfers and a boost port. I recently acquired some 350 sleeves from a later engine that was a "5-port" (A and B transfers plus a boost port). When did Yamato do this, go from three to five transfer ports? Also, when did they go to reed valves?

Incidently, these sleeves are thinner (smaller O.D.) than the older sleeves, which were sized to press into the same sized hole as sleeves for a 500cc engine. When did that happen? Yamato went through some odd sleeve changes in the first years. The first 350 engines had two-part sleeves, aluminum cast around an iron sleeve. Evidently they decided that the iron-aluminum interface was enough of a barrier to heat transfer that the two-piece sleeve wouldn't shed heat any better than an all-iron sleeve, because they quickly went to that (well, maybe it was just simpler to build). Yet I heard that even later they went back to the two-piece sleeve! So I take it that the thin iron sleeves that I just acquired was their final answer. Yes? No? Doesn't matter; I'm just curious.

(EDIT) (The thread that might still be referred to in the title bar has outlived its usefulness).