>My father made a suggestion that perhaps these engines were originally
>sleeved and thus, of less displacement like earlier models of 1296.
>Then, to increase displacement (and performance), the sleeves could
>have been removed and over-sized pistons could have been used to bring
>the engine to 1493 without major production changes. (the 1500) --
>this may account for the recession of the cylinders--where the sleeve
>flange would have gone? make sense? Or just an off-target guess?
******************************************
Well, a good guess, but incorrect. A brief little Spitfire engine history
if you will- If I err, someone will correct me as I'm using my rapidly
failing memory. All my references are at home.
The increase (and major changes to the block and heads) came with the
introduction of the Spitfire MKIII and the increase from 1147cc (which was
about the limit that this particular block could safely handle) to 1296cc.
At that time the engineers found that by "siamesing" cyl 1/2 and 3/4 they
could increase the displacement, but this would require a new block,
crankshaft, and cylinder head with different head bolt spacing (might as
well make separate intake ports also). This would also require a
different. (and might as well make it better breathing) intake manifold
with separate ports for each cylinder to match the new head configuration.
There is a lot of commonality between parts but for all practical purposes
the MK 1/2 engines and the MK 3/4/1500 engines are different. This
cylinder spacing would allow a further displacement increase to I believe
just over 1600cc, but that was never realized. In 1972 the block was
changed to allow the use of the same bearings and connecting rods as the
TR6/GT6 line (probably in a move to commonize (sp?) and reduce costs).
Also in 1972 the cylinders were recessed in the block and the head gaskets
"O-ringed" to help in head gasket sealing. In 1973 (in the USA, as British
spec's were different) the increase to 1500cc (1493cc) was accomplished by
stroking the engine but leaving the bore dia. the same. The engine
remained essentially the same until Spitfire production ceased in 1980.
The block was never sleeved (to my knowledge) but sleeves are available in
case you damage a cylinder beyond repair-
Barry Schwartz (San Diego) bschwart@pacbell.net
72 V6 Spitfire (daily driver)
70 GT6+ (when I don't drive the Spit)
70 Spitfire
|