Hi Dan,
People do occasionally move the 6 cylinder engines back. It's a lot of work. Mainly bulkhead mods, but chassis fit is a bit challenging further back if you want overdrive, especially if J-type. Not gone to that extent myself, just nudged things back as far as I could without doing any bulkhead chopping by slotting the negine mount brackets (was shoehorning the Toyota 5 speed in at the same time so gearbox mounts were being recreated anyway. Probably gained no more than 15mm. That said, with that, a few alloy parts up front (water pump housing mainly) and careful setup of the suspension, it's actually pretty nimble. Not sure if a 6 will go under a GT4s bonnet if not moved back?
You can't put a Vitesse / GT6 box on a 4 pot, or at least not easily. The input shaft size and spline are the main fitting issue. It is (or was) possible to get hybrid shafts as the Spitfire racers liked the close ratio gearsets from the 6 cylinder. Whether you want such a tall first gear with a 4 pot is another question - probably not for a 1200 or 1300, but maybe ok with a 1500. Does depend a bit on the final drive. In my opinion most of the cars were under geared from the factory and need to go up one. Ie 4.11 -> 3.89 for the 1200 &1300 cars (though standard 1200 might struggle a little), 3.89 -> 3.63 for the 2L cars (3.27 is ok for GT6) and only the 1500 is about right with the 3.63 from the factory.
Fuel injection and economy. It depends.... The 2L is actually capable of good economy on the original Strombergs when all set up right, though more on long runs. There is no doubt that injection pushes the average up by doing quite a bit better on the shorter runs and a bit better on the long runs. With my original, fairly standard 2L mk2 engine on injection I was averaging low to mid 30s daily running around, mid to upper 30s on longer runs (including 10CR type long runs where it was being driven hard and fast) and a best ever of 43 mpg pottering in France. Current, rather snortier engine isn't much behind on the long run stuff but doesn't do so well in the day to day stuff because it's over-cammed and has to run a bit rich low down for driveability. Still in the early 30s though. Performance wise, I was getting about 120bhp out of the standard-ish engine (some head work and 6-3-1 but original 308778 cam) and really nice manners. Pinking and running on was banished instantly even though the timing map is more aggressive that factory and running 95 fuel. I've recently rediscovered pinking and running-on with my bone stock GT6 engine.....
Best economy I know of is a 1500 Spit on megasquirt injection. He's pretty much always in the 40s and claims to have seen early 50s....
Nick
People do occasionally move the 6 cylinder engines back. It's a lot of work. Mainly bulkhead mods, but chassis fit is a bit challenging further back if you want overdrive, especially if J-type. Not gone to that extent myself, just nudged things back as far as I could without doing any bulkhead chopping by slotting the negine mount brackets (was shoehorning the Toyota 5 speed in at the same time so gearbox mounts were being recreated anyway. Probably gained no more than 15mm. That said, with that, a few alloy parts up front (water pump housing mainly) and careful setup of the suspension, it's actually pretty nimble. Not sure if a 6 will go under a GT4s bonnet if not moved back?
You can't put a Vitesse / GT6 box on a 4 pot, or at least not easily. The input shaft size and spline are the main fitting issue. It is (or was) possible to get hybrid shafts as the Spitfire racers liked the close ratio gearsets from the 6 cylinder. Whether you want such a tall first gear with a 4 pot is another question - probably not for a 1200 or 1300, but maybe ok with a 1500. Does depend a bit on the final drive. In my opinion most of the cars were under geared from the factory and need to go up one. Ie 4.11 -> 3.89 for the 1200 &1300 cars (though standard 1200 might struggle a little), 3.89 -> 3.63 for the 2L cars (3.27 is ok for GT6) and only the 1500 is about right with the 3.63 from the factory.
Fuel injection and economy. It depends.... The 2L is actually capable of good economy on the original Strombergs when all set up right, though more on long runs. There is no doubt that injection pushes the average up by doing quite a bit better on the shorter runs and a bit better on the long runs. With my original, fairly standard 2L mk2 engine on injection I was averaging low to mid 30s daily running around, mid to upper 30s on longer runs (including 10CR type long runs where it was being driven hard and fast) and a best ever of 43 mpg pottering in France. Current, rather snortier engine isn't much behind on the long run stuff but doesn't do so well in the day to day stuff because it's over-cammed and has to run a bit rich low down for driveability. Still in the early 30s though. Performance wise, I was getting about 120bhp out of the standard-ish engine (some head work and 6-3-1 but original 308778 cam) and really nice manners. Pinking and running on was banished instantly even though the timing map is more aggressive that factory and running 95 fuel. I've recently rediscovered pinking and running-on with my bone stock GT6 engine.....
Best economy I know of is a 1500 Spit on megasquirt injection. He's pretty much always in the 40s and claims to have seen early 50s....
Nick
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