Timing & Mixture 998cc A Plus

[cabrio1275]

Can anyone advise the best approach to getting the timing & fuelling right on my 998cc A plus engine. The only mods are a Morspeed 12G295 head which I was told should have a CR of about 10.5:1 and a pair of 1.25" SU carbs on an original Cooper inlet manifold. It has new air filters (from a Triumph Spitfire). It also has a Maniflow exhaust manifold & single box side exit Maniflow exhaust system. It has just had the mixture leaned enough to get it through the MOT. Also recommendations on spark plug gap with this set up please.

[carbon]

One of the few sure approaches to getting timing and fuelling right is to take it to a competent rolling road.

That said it is possible to get the fuelling in right ballpark by careful choice of carb needles & springs, but can be a faff. The 998 Cooper spec rich needles might be a starting point as you have a modified 295 head, but exhaust system will also make a difference. Rocker ratio also makes a difference to fuelling.

As for timing this will depend a lot on CR, you really need to know an exact number and decide what fuel octane you will use. And the ignition advance curve will not be standard, has to be set up to suit the motor.

Spark plug gaps depend on the coil and system being used, likely to be from 25 thou for standard non-ballast coil up to 35 thou for some electronic sports systems.

[Retroman]

I would be trying M needles with your spec,

and as per Carbon 25 or 35 thou NGKBP6 ES plugs

And reiterate a Rolling Road session as the best way to optimize the whole setup

[cabrio1275]

Thanks for the recommendations. Any ideas on Mini friendly rolling roads near me? I am about 30 miles south of Birmingham, 7 miles east of Worcester

[carbon]

I've used Aldon Automotive in the past, but that was over 30 years ago...

My experience was that Aldon were good for SU carbs, and also very competent on ignition and ignition timing.

Aldon Automotive. Breener Ind Est/Station Drive, Brierley Hill DY5 3JZ. Phone: 01384 572553

[Chewie Baker]

has anyone used Aldon recently?

[Fanfaniracing]

Going to a good rolling road will save you a lot if money and bring a lot of Fun with your Engine