THE SIDE-VALVE ALVIS
I was interested in the reference made by the writer of the June ” General Notes ” to the old side-valve Alvis 12 h.p.—which he calls a ” 12-50.”
As the owner of one of these cars, of the ’24 vintage, might I be allowed to comment that the Alvis Company always appear to have referred to this car as a ” 1240,” whilst only the o.h.v. engine was expected to do the work of fifty horses. I have always been very interested in both the ” 12-40 ” and the ” 12-50.” Even the Side-valve engine could Make most other 12 h.p. jobs look sick when it was ten years old, and withal it did a very easy 30 m.p.g. under all sorts
of conditions. Incidentally I have the old Zenith vertical carburetter on my engine, whereas the makers fitted a Solex. The induction passages were for the most part inside the block, but a small external aluminium casting formed a rather good hot spot, which was rather interesting in that a portion of the exhaust gas was brought in a small pipe round the rear of the engine, through the hot spot and thence down to a tiny little aluminium silencer of its own by the side of the sump. The engine Would always start exceptionally easily and has never given a ha’porth of mechanical trouble in the whole of its life, even when it was
neglected for two years at a time. It once started with six turns of the handle after standing unused for six months. The crankcase, sump, crankshaft—in fact, everything except the block and head are interchangeable between the
” 12-40 ” and the ” 12-50.” The sidevalve eagine has a fixed head, with brass plugs over the tops of the valves, so that the valves could be ground in with no trouble at all.
The side-valve engine would rev, up to about 4,000 r.p.m., representing a road speed of about 75 m.p.h. theoretically, although I have never done this myself, having had the carburetter set too fine for high maximum speeds. The ” 12-50 “uses slightly more juice and revs. up to 4,500 r.p.m., hence the greater h.p. and better all out maximum. I have a 4.5 axle with which the ” 12-50 ” will do nearly 90 m.p.h. on paper, but a normal touring body makes such a ratio give the tar a feeling of being under-powered.
It is very easy to replace a s.v. engine with an o.h.v., by fitting a different exhaust system and shortening one radiator connection. Everything else is the same. I have done this myself, though I must admit my car is very definitely non-standard by tow. I am, Yours etc.,
R. K. MATTERsoN. Rochdale.