803cc to 948cc

[steve jw]

Hi,

I have only ever had 803 engines and 1 1098cc engine car - I was wondering how much difference there is between the 803 and 948 and what other changes are on the engine, does the extra power make much difference to the feel or running of the car? also does the 948 still use the early gearbox?

[rogerowen]

Hi, I started this thread a while back;

http://www.mmoc.org.uk/viewtopic.php?f=4&t=42842

Lots of useful comments, especially about the gearbox. There are a couple of outfits who will create a recon box with 1098 (or 948) workings encased in an 803 / 948 outer case.

[bmcecosse]

Or just fit the 803 gear lever to the 948 gearbox.....

[rogerowen]

Or just fit the 803 gear lever to the 948 gearbox.....

That flagged up a few issues before. It's do-able but............

[bmcecosse]

It's just bolt off/bolt on. Straight swap.......

[rogerowen]

It's just bolt off/bolt on. Straight swap.......

Do you mean the whole tail shaft unit from the 803 to 948/1098 box. Not just the gear-lever? Isn't the 803 the magic wand type gear change whereas the later 948 and 1098 have a remote linkage (further back / shorter gear lever) that would not fit the floor of the 803 car (without modification)?

[steve jw]

Thank you for the replies and for the link to the other thread - is there much noticeable difference in the power between the 803 and 948?

[bmcecosse]

A LOT more power..... But you will also need to change the final drive ratio (and speedo) to get the best from it. And yes -complete tail unit swap to the 948 box is bolt off/bolt on. It's Not nearly so easy to a 1098 box - although it can be done and is detailed on various threads.

[liammonty]

the tail shaft of the gearbox is indeed 'bolt on bolt off', however unless you change the reverse selector, you'll find you have nothing stopping the gear lever moving over in to the reverse gate, as the 803 gear lever has to be lifted to get the reverse gate, whereas the 948 one has a spring in the tailshaft to stop you from inadvertantly engaging reverse. You will regret it if you don't swap this over.

You will also regret not changing the speedo drive worm gear in the gearbox, because your speedo will over read by 50% if you don't do it, rendering it useless. The drive from the 803 box will not fit unless you change the internal drive gear, as the teeth won't mesh. So, it's not quite as straightforward as you've been told, but it's really not that difficult.

There is no comparison between the hateful, asthmatic, fragile, snappy-crank 803 and the 948, which is a lovely, sweet and tough engine. As BMC says though, change all the running gear (i.e. diff and gearbox too) to make the most of it, otherwise you'll still be crippled by the ridiculous diff ratio, which becomes even more tiresome when you've got more power. Just make sure you've got the later Austin back axle, else the diff won't be possible to change (only very early 'Cheesegrater' grille cars had this axle). I did exactly this conversion to my early 803 when, inevitably, the big ends went in the original engine, and it totally transformed the car, which I thoroughly regret selling. BTW, you shoud be able to pick up the running gear cheaply second-hand. Phone around some of the smaller suppliers for bits, don't fall into the trap of only trying the big suppliers on the internet, who charge much more for second-hand stuff (as they have to buy it from the smaller traders themselves!).

[steve jw]

Thanks for the replies - I didn't think there was so much to changing the unit but I think it sounds like a good thing to do, thanks, steve.