948cc to 1098cc

[faversham999]

I have a 1098cc engine what do i have change to fit it to my 1961 948cc car.
Little as poss please
or is it best to replace it with another 948cc engine

[Fingolfin]

I assume you mean '948' and not '998' -- as the Minor never had the 998, though the Mini did. Perhaps yours has been replaced with the Mini unit? If made in '61, it would be logical that it would have the 948 engine.

Having never done the job I'm not sure of the details, but to make the car run really properly with the 1098 you should replace the smooth-case 948 gearbox with the ribbed-case 1098 unit, and (unless you're looking for a little more speed, but less torque) also the later rear axle. I suggest the axle because the earlier axle will throw off your speedo. It may also be necessary to replace the prop shaft, but don't take that to the bank.

I'll bet dollars to doughnuts that the smooth-case gearbox can't handle the extra power of the 1098 engine. So if you haven't got a ribbed-case gearbox to kick around, you may be better off sticking with a 948.

[PSL184]

The 1098 box is stronger than the 948 box but you could still run a 1098 engine with a 948 box OK. Prop is the same but as mentioned you would be better off with the 4.22 diff out of a 1098 car rather than your standard 4.55 ratio.If you keep your 948 box you will need to retain the 948 clutch and the 948 backplate of the engine for it all to work together or just fit the 1098 box with 1098 clutch....

[mike.perry]

And a pair of 1098 8in front brakes!
Just changing the engine and gearbox will not affect the speedo, you will only have to change it if you change the diff.

[faversham999]

If I put the Head of the 1098cc engine and fit the camshaft to my 948cc engine , do i need the 1098cc cam followerd and rods or 948cc ones

[bmcecosse]

Followers and push rods are the same both engines - use the best 8 followers from all you have. Inspect each one carefully on the base and reject any with pits or crazing. The head will need 60 thou skimmed off the face to keep a good compression ratio.

[faversham999]

Thank for that I will do that to the engine ( get someone to do it) this winter let you know how I get on . Have had the front brakes changed from 7 to 8 inch they had to use the 7 inch adjuster as the 8 inch were to big.

[faversham999]

I am upgrading the 948cc engine with a Head. Manifold and camshaft from a 1098cc .How much extra power would this give me I am having the head skimed by 60thou

[bmcecosse]

Potentially the same power as the 1098 - but at ~ 15 % more revs. The head/cam/carb/manifold are the limiting factors for power - so at ~ 15% more revs the 948 will be shifting the same volume of air as the 1098 at the lower revs = same power, neglecting any additional frictional losses of course - which may not be a good thing to do! Actually - the 60 thou skim will raise the comp ratio ratio rather higher than the 1098 - so this may help to compensate for the additional friction.

[faversham999]

Thanks I will let you know when I have changed the parts over

[faversham999]

I am putting a 1098cc head ,camshaft and manifold on my 948cc engine should I put the 1098cc carb as well are they any diferent

[bmcecosse]

The manifold is certainly better - be sure to use it. The carb is likely to be newer - so if in decent condition - use it too!

[faversham999]

Have a 1098cc head and camshaft fitted now on my 948cc engine. Its much better at 35 to 50MPH now . I fitted a new thermostat but that lasted only one day faulty . Only found out because I have a water Temp Gauage

[bmcecosse]

Hopefully you skimmed the 1098 head about 60 thou - assuming this - you should now get the 1098 power - but at some 15% more revs than the 1098 engine.

[faversham999]

Well the engineering shop said they skimmed it

[bmcecosse]

Excellent! I would check the thickness - if now 2.690" - that means 60 thou has been removed.