17 replies to this topic

[Burgerdale]

Hi everyone,
I'm looking for some advice/ experience on what final drive to go for.
It's going to be my daily toy as I won't need it for long journeys other than shows. Given the spec I expect it to be quite noisy inside anyway so road noise won't be too much of an issue. I'm more concerned about traffic light races and being able to put the power down.
Spec:
10x6 kn mercurys
1380
Powermax pistons
Wedged lightened balanced and nitrided crank
Balanced con rods
286 cam and vernier timing
Strengthened pushrods
Stage 3 head / ported and balanced chambers
rim flow valves
Weber 45 on long manifold and ram pipes.
Med ultralight flywheel and clutch assy
minispares clubman straight cut gearset.
x-pin diff

Ive current got a 3.1 final drive crown wheel and pinion but I also have a 3.44. I'm considering buying a 3.6.

like I said I prefer acceleration but I don't want to just have a ton of wheel spin.

[Dr s]

That's a hot cam, I'd go for the 3.6 for a toy. Best option probably would be with the 1275 close ratios box. Sounds like fun!

[racingbob]

yes probably a 3.6 with that cam

 

my race mini had 3.76 and a 3.9

 

with 310 kent cam close ratio box

 

and was fine

 

you would probably get away with a 3.4 to

 

definitely not a 3.1

[Spider]

I did have a similar spec engine in one of the Minis and ran initially with the 3.6, but found it too easy to light up the tyres and while the gearbox did have S Ratio Gearset (Helical CR), I felt 2nd and 3rd 'ran out' rather quick. I then tried the 3.1, but found the acceleration disappointing. Ended up settling on a 3.4 and found that to be the happy medium.

[Burgerdale]

Great, thanks for the input. I'm torn between using the 3.4 I already have and the 3.6 I can buy.
To use the 3.4 ill need to strip it out of an old box but to buy its £30 and im not sure of the quality as its an eBay job.

[GraemeC]

3.6
With that cam, the tall 1st gear of the SCCR and the light fly your clutch will thank you for it.

[1968andyf]

Got almost the same spec engine and use a 3.44 diff its just right. Plus you already have one

[Almond-1]

Run both 3.44 & 3.6 on similar spec. 3.44 was the best all rounder. Again NOT the 3.1.

[Cooperman]

I run a 3.9:1 with a 286 and lightweight flywheel and SCCR gears..

A 3.44:1 will still give a long 1st gear, but that won't be too much of an issue unless you need to start off up steep hills.

[Burgerdale]

I'm really tempted to get the 3.6, it saves me stripping the old box and diff. Its only £30 and when we do go to shows we tend to do around 60 all the way.(if we're lucky)

I've had a vtec conversion and that would spin into 4th in the damp.
If I can just feather it a little if setting off in first ill be ok with that.

[racingbob]

my fast road cooper s back in the 90's in AUS

 

had a spv4 scatter cam vizard cam like a 296

 

ran a 3,44 was fine for road

 

if I recall pulled nice from 3000

[Midas Mk1]

Ran a 3.6, 3.44, and 3.2 with a 286 ish cam (sw10),  with the 3.2 being my choice.

Did over 3k in two weeks doing l2b and the thistle run last year with the 3.6, just runs out of legs anything over 80.

[Guess-Works.com]

If you're ever unsure of what final drive to run, start with a 3.4 it will do in 99% of cases.

[Haynes]

I have almost identical spec and run 3.7 with 10x6 wheels.  With the SCCR box 1st and 2nd are quite tall, up to 40 and 70mph respectively.    I dont have a problem with wheel spin.

 

Youre going to have to rev the nuts off it to get it off the line anyway as it wont get on cam til 2500 - 3000rpm, so trying to burn people off at the lights will be a little too ostentatious.

 

Forget cruising around with a 3.1, if thats what you want re think the cam.  I think the 3.7 is a compromise for road use, the 3.4 even more so, when youre not compromising on the engine spec.  

 

In fact I'm thinking of changing to 3.9 or 4.1 so that its on cam at lower road speeds.  On the rolling road 7500rpm is around 110mph, when you consider power band is 3000 to 7500, just dont use that speed.

[mk1coopers]

3:44 in mine, more than happy with it