>"110 HORSEPOWER FROM 1200 CC! THE ULTIMATE "A" SERIES MOD.
Uhhh, well, not quite. The standard three-out, two-in A Series
head is quite capable of shearing axle shafts on its own, thank
you, isn't it, Miq? Car 0 puts out more than 10% more than this
cylinder head, at the rear wheels. Of course, it's also completely
unsuitable for street driving.
>'Jomo Eight Port Head'. Designed for any 'A' Series engined car, and
>designed for those who want the ultimate in power from the BMC 'tiddler',
>the new head is cast in high quality aluminum (hardened and x-rayed) and
It is a good idea, so good it's hardly new. There are at least
three different aftermarket cylinder heads aside from this one
that I know of for the A Series:
- The factory had Morris' Eddie Maher build a prototype head
when Honda was testing the S800 roadster in Britain. This
car (with 78 bhp out of an 800cc twin-cam four) scared
the Castrol out of BMC, so they decided to see what they
could do to an A Series. Maher's head would have been
cheaper to produce, had a proper crossflow design --
and made the Spridget faster from 0-60 and in top speed
than any of the other BMC sports cars of the time (the
E Type wasn't yet part of the conglomerate). When Honda
pulled out of the market, BMC killed the head.
- The works Sprites had a crossflow cylinder head that
they used in the 1967-68 Le Mans races, as Robb suggests.
I don't think the race and street heads were the same.
- Janspeed (I think -- if not them then another big tuner)
produces a SOHC crossflow head that bolts onto an A Series
block. It is alloy and apparently does produce some nice
power figures, as well as being simple and well designed.
>Fitted with such a head, the bhp of a Weber carburetted, 1293cc (late) 'A'
>Series engine is typically around 110(!) at 6800rpm, enough to give the A40,
>Sprite, Midget, or modern Metro, a somewhat unbelievable performance.
Well, the lightweight Sprite coupe that ran at Le Mans had a
top speed of 147 mph, an average speed (in 1967) of 110 mph
around the track -- faster than the 1961 winner, which points
out what kind of development was going in in the Sixties -- and
returned over 20 mpg *during the race*. Not bad...
>Now, if I remember correctly, toward the end of the Healey family's
>involvement with the BMC Spridget racing program, they were getting about
>110 hp out of a fuel-injected 1275cc 'A' Series engine.
110 in 1967, using twin 45DCOEs. In 1968, they went to Lucas
petrol injection and got 120 bhp, then the BMC-to-BL thing
happened and right after the 1968 race, the competition programme
got shut down. This was with 1293cc, mild compression and a
racing cam. For comparison, some of today's racing Sprites
for SCCA F Production are putting out well over 130 bhp with a
ported and polished stock cylinder head. Again, though, these
engines aren't suitable for the street, but it's possible
to get about 110 bhp out of a stock cylinder head even if
the street is your main goal -- displacement, cam, porting,
header, intake, and balancing. Of course, by then you'll
have spent a lot more than $2500 on the motor, too.
--Scott "How fast can you afford to go?" Fisher
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