DOWN ON POWER
Q I have a 1979 Mini Clubman, still fitted with its original 1098cc engine and gearbox. Both appear to be in good condition, with the engine consuming little or no oil. However, it seems to be working extremely hard at anything over 60mph. I’ve set the timing as per the workshop manual, and I think the fuelling is right too. However, it’s just wheezy and gutless! I know it’s know a performance car, but I’ve driven loads of Minis over the years and even a 998 would make mincemeat of mine. A friend suggested it’s down to valve seat recession, but surely it would smoke if that was so? Stephan
A Before fitting any form of tuning upgrade, you need to make sure what you have is fit and healthy. First, get a leak-down test done, and if that looks good, get it set up on a rolling road with a Mini-savvy operator.
No to be confused with a compression test, the leakdown test is used to determine the health of each individual cylinder. This is done by setting each cylinder in turn on its firing stroke with the piston at top dead centre and both valves closed.
A tube with a threaded adaptor at one end is screwed into the spark plug hole, while the other end has a coupling that attaches to an air line so the cylinder can be pressurised with compressed air. The main section of the equipment is two gauges that show the air pressure being applied, and a second showing the amount of air being leaked out by way of a percentage. Up to 10 per cent leakage is pretty good, 20 is okay and up to 30 is concerning. More than that, and you’ve got major issues.
It is not just the gauges that reveal any problems; air heard escaping can lead you to the specific problem. If heard coming out of the carburettor, it’s the inlet valves not sealing. Out of the exhaust, it’s the exhaust valves not sealing. If it’s out of the rocker cover and dipstick tube, the rings are not sealing as they should.
Getting the car set up on a rolling road will optimise fuelling and ignition, and give a power output reading. Whilst rolling roads rarely produce actual and real performance readings, the figures obtained can be directly compared with other similar units run up on it to give some idea of the health of the engine.
Before heading off to the rolling road though, there are a couple of things to check and sort. Make sure the ignition system is in good health – so points, condenser, rotor arm, dizzy cap, spark plugs and plug leads. Also check and set the valve clearances, as these can make a big difference too.
The other thing to check is the oil – foremost the oil level. Some reports of engines that won’t rev and feel flat turned out to be because of excessive oil in the gearbox!
Check your engine is fit and healthy before making upgrades.