Jacob, Try very hard not to use an Austin 8 engine. The block is about half an inch longer and it will give serious problems with the location of the rear mounting that picks up the gearbox. You will need to transfer (and perhaps modify) the plates for the front support and the bell housing support. The clutch plate also quite different and, if memory serves me right, you may be forced to use an A8 gearbox which then takes the gearbox mounting point even further back. I tried all this nearly sixty years ago and gave up in favour of a Big Seven engine. Happy hunting for the right block.
Ron

Location: Thornbury

It is surprising that after such a major engine redesign the Big Seven engine had such a short life. The new Austin 8 engine doesn't seem to share very much - I wonder what was learned ?

Tony.

Location: Malvern, Melbourne, Australia

Hi Tony

A bent wire crank would be less costly to forge than a fully counterbalanced one.
The Seven type hardened steel cam followers with fancy broached bronze guides would have been more expensive than simple chilled iron followers running in the block. I guess Austin took note of the competition. When their vast model range in the 30s is considered, it is surprising Austin did not adopt a more conventional, cheaper, construction for the Seven earlier.

Bob Culver

Location: Auckland

Ron, a good friend of mine fitted an Austin 8 engine in his Big 7 when the original broke a crank. It went straight in without any issue the only difference being that the fan was closer to the rad??

Ruairidh, OK, looks as though he managed to reposition the front mountings, but all my other comments apply, including my query re needing to employ an A8 gearbox (possibly because the clutch release parts are different - it was a long time ago!). Not my idea of going straight in. It would be interesting to check just what he did so there are no surprises for Jacob. Much better to go looking for a Big Seven mono-block.
Ron

Location: Thornbury

I'm sure your recollections are correct Ron.

He tells me that he used an A8 engine and gearbox, went straight in, no moving of mounts. He and car are well known up here and I have no reason to doubt him either. I wonder if there is any variance in Austin 8 or Big 7 engines that could explain the varying experiences?

Interesting! I'm confident that during the production run there was no variation in the Big Seven mounting plates which bolt on to each end of the block. Maybe the pre-war A8 matches the Big Seven as regards mounting, and I had a post war one that was different. I'm pretty sure the holes to take the bell housing bolts for the Big Seven gearbox had different centres from those on the A8 box - hence the transfer of gearbox - as well as the need to also transfer the clutch and driven plate. The front end definitely needed the old plate to be transferred in order to mate with the rubber mountings.
So............ anyone know more about Austin Eights???? I suggest Jacob gets some pictures before buying any (otherwise unseen) A8 engine - and he needs to buy the clutch and gearbox as well.
Ron

Location: Thornbury