mk1-forum.net

Hi

I just finished completely revamped engine. Driven 600km in the meantime. It does run very smoothly.
I still have the question of which needles I should put in. Eventually, after x number of km, I want to go to a rolling road. After 1000km ?

Here are my stats of the engine:
1295 engine
engine +020”
Polished, ported and modified
crankshaft nitriding, polishing, balancing

1.5 Hi lift forged rocker
illuminated flywheel

illuminated double timing chain
twin HS2 carburettors

differential 3.44

https://bmot.jalbum.net/Engine%20for%20Cooper%20%2767/

Cheers
Wesley

Wesley it realy comes on what Cam, Head, exhaust system carbs ect you use.

A rolling road is the best way to find out if your AFR is spot on.

Found out last weekend that with some minor modifications i still can improve the Power on my engine.

Dyno'd mine after a couple of 100km's the first time...

If you install an AFR gauge you can check the mixture and adjust or replace the needles (and spring, damper oil) accordingly

timmy201 wrote: ↑Tue Apr 01, 2025 1:54 am If you install an AFR gauge you can check the mixture and adjust or replace the needles (and spring, damper oil) accordingly

Have you installed the lambda sensor in the manifold of do you have some way of mounting it in the tailpipe?

Both work.

I for my application have it fitted after the Y Piece but on the dyno he clamp on in the Tailpipe to register the Mixture over the RPM range...

I have a friend who tests his freshly built engines on the Road with a clamped Sensor

M needles would be a good start.

gs.davies wrote: ↑Tue Apr 01, 2025 8:12 am

timmy201 wrote: ↑Tue Apr 01, 2025 1:54 am If you install an AFR gauge you can check the mixture and adjust or replace the needles (and spring, damper oil) accordingly

Have you installed the lambda sensor in the manifold of do you have some way of mounting it in the tailpipe?

At the moment I’ve got a sensor bung in the manifold after all the cylinders have merged. When I don’t have the gauge fitted there’s a little Allen grub screw that blocks the port



I have previously used a tailpipe adapter, although this doesn’t give a decent reading at idle.



If you can get a custom made one that’s a bit longer and pokes further in, and is longer after the sensor it might read better

I learn every day, didn't know about this tool. But personally I am thinking of going to a roller road.
Thanks for the replays, very useful info

WesleyB wrote: ↑Mon Mar 31, 2025 8:19 pm illuminated flywheel

illuminated double timing chain

HI Wesley,
I guess that lightened flywheel got lost in translation
>>disque d'inertie éclairé

chaîne de distribution double éclairée>>

Made me giggle, though. No harm meant, I just lack the very British politeness to NOT mention this little slip.

On a serious note: what needles have you currently fitted? What spring and which oil viscosity? Because if you don't know the starting point it is difficult to make it better even on the dyno.

Thanks MiNiKin ! you're right

I would have to check which needles I have now. The mini certainly doesn't drive badly now, but who knows, it could be better. I'm pretty sure of that.
This weekend I do a regularity rally, after the weekend I look further.

WesleyB wrote: ↑Tue Apr 01, 2025 1:11 pm I learn every day, didn't know about this tool. But personally I am thinking of going to a roller road.
Thanks for the replays, very useful info

It’s the same tool the rolling road should be using to tune your carbs

One good thing about having it fitted in your car is you can tell if it’s been properly tuned at all running conditions:
Idling
Full throttle
Part throttle cruising
Etc