Basic Engine Swap / Gear ratio question !

[jl46]

Hello All,
Lets just say someone was to remove an original 1962 Countryman (850 cc,3.76 FD) and
swap in a MG 1100 (1098CC, 4.13 FD) engine.

I'm sure this engine swap would provide a much quicker Countryman around town and
on the back roads.. but I'm wondering about the engine revs at the higher motorway and
interstate speeds. How would you rate the overall driving experence after
making this swap.

What say you ?

Thanks,
Jim

[iain1967s]

There’s a ratio calculator on the guessworks site

http://guess-works.uk/Tech/ratio.htm

Don’t forget you need sandwich plate remote for an 1100 diff casing

[Thorp]

Jim,

I think you might find this too low geared. The 1100
Engine is longer stroke and has the highest torque of the small bore lumps. Consequently it can pull a higher geared (3.44 for example) FD with ease. Don’t know what the limits are on the interstate where you are but with a 3.44 FD it’s approx 16mph per 1000 rpm in 4th gear. Assuming you can cruise at 60-70mph, thats still quite a few revs.

[Costafortune]

If you can find one, a 3.1 FD or at least a crown wheel and pinion.

For simplicity, the 850's diff and pinion straight in the 1100. It will be very nippy in 4th gear.

[CooperTune]

I have been pulling 3.44 CWPs left and right. The new popular is the 3.2, 3.1, 2.95 and 2.76. I install a 3.76
for a customer over my objection. After his four hour drive home he called wondering what it would cost to
change to something more reasonable. My personal mini has a 1360 Cooper S on a rod change wide ratio with
a 2.75 CWP and two OD drop gears. Seventy MPH at 3000 rpm and 96 at 4000. Steve (CTR)

[timmy201]

I put a modified 1098 & 3.44 ratio in my 850 last year, swapping from a 998 & 3.76

In hindsight if I’d known how much low down grunt the 1098 had I would have gone for a 3.1 or 3.2

With a 4.13 you’d be at nearly 4500rpm to do 60mph in top gear, and 5000rpm to do 70mph.

And stock vs stock a 1098 puts out about 40% more power than a 848, so less rpm is needed everywhere

[roymck]

Years ago I had a MG1100 engine and box in a early mini didn’t change the FD brilliant acceleration rubbish top speed . My next mini I put a 1300GT engine in but changed the FD to a 2.7-1 it didn’t appear to be over geared . My next build will be 2.7-1 geared .

[nick@dunsdale]

Unless you are doing hill climbing i would say 4.13 will be way to low geared, i drove a mini powered with a 1300 riley kestrel engine in it, with what i would assume to have a 4.13 crown wheel and pinion it, the acceleration up to 60-70 was phenomenal but it was topped out and screaming by the time it hit 70

The best one i tried was a 2.9 out of a mini city in medium tuned 1300gt engine in a mini brilliant diff loved it.

[jayare]

My pickup had an 1100 engine with a 4.13 FD in it when I bought it - it was absolutely awful!! I swapped it for a 3.44 which is nice and nippy without screaming it's wotsits off at 60-70mph. 3.76 would probably still be too low a ratio to be comfortable on the faster roads,

JR

[Spider]

When you remove the 4.1 CW & P, I'd be interested in buying them !