Balance and mixture-set triple carburettors
The three carburettors on any Aceca must draw equal airflow at idle before mixture can be sensibly set. This is done with a balance meter, each carburettor's throttle stop adjusted independently, then mixture walked in per carburettor until idle is smooth.
Tools
- Carburettor balance meter (airflow gauge)
- Vacuum gauge (useful cross-check)
- Screwdriver set
- Small spanner set
Parts / supplies
- SU damper oil (if applicable) of the specified grade
- Fresh linkage rubbers if any are perished
If you have a photograph of this job on your own car, the archive would be glad of it and will credit you; get in touch.
Procedure
Bring the engine to full operating temperature so the chokes are fully off and idle is stable.
Slacken the interconnecting throttle linkage between the three carburettors so each one idles independently.
Place the balance meter over each carburettor intake in turn. Adjust each carburettor's individual throttle stop until all three draw the same airflow at the target idle rpm.
Set the mixture control on each carburettor in turn for the smoothest, highest idle. Rebalance airflow after each adjustment; the two interact.
Reconnect the throttle linkage so all three throttles open together from a single pedal input, without disturbing the individual idle stops just set.
Road-test the car and re-check idle balance and mixture. Confirm all jet, needle and float settings against the workshop manual.
Warnings
- Do not run the engine with the air cleaners removed for longer than the balancing procedure requires.
- Never substitute jets or needles without a documented reason and the workshop-manual figures.
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About the author
A lifelong classic-car enthusiast in North Yorkshire, near Thornton-le-Dale, who owns and maintains an AC Aceca, writing the single-model reference he always wished existed. Read the full bio.