Tuning of MGB`s and Midgets
We tune SU carburettors but go the extra distance -
One of the most common request we receive is “can you tune my carburettors? ” The customer is really asking us to get the engine running as it should. The engine will never run at its optimum performance if the tappets are not set correctly. The spark plugs, the dwell and the timing also all have to be correct. Take one look at an engine rocker cover and it is usually apparent that it has not been removed for a long time, so it goes to say the tappets have been ignored. To set the carburettors all the other settings must be addressed first.
The good news is that once a “B” or “A” series engine is set up as it should be, they perform well and our customers notice the difference.
The original SU carbs upon most MG`s have had a lot of use and wear upon the butterfly spindles (the moving parts that open and close as you accelerate). This is not a problem, but some is sucked down the gap in the spindle bushes. This causes the engine tick over speed, to speed up, particularly when the engine gets hot. This is because the aluminium casing expands with the heat increasing the air gap. In these instances; as a compromise we set the engine tick over low for start-up, knowing it will speed up when it gets warm.
If you want to know if your engine is running as it should and the mixture is correct - take out the spark plugs. Upon removal keep them in order, then examine their colour and condition (against pictures of plug conditions upon the internet). This will soon tell you if one or both carbs are running as they should. If the plug 1 & 2 or 3 & 4 are different in condition then the carbs require attention.