QuestionHi from New Zealand.
Great website and great advice you guys hand out!
When I depress the clutch (eg at the lights and ready to engage 1st gear)on my MkIII midget, the revs drop back and the engine will die unless I blip the throttle. Main bearings are good, no rumble and good compression. Engine also runs one a little bit when I switch off. I am told the problem is ignition- can I adjust this by the little dial on the automatic advance/retard unit leading into the distributor, or is it a specialist job and really needs a much more comprehensive tune up?
many thanks
alastair
Christchurch
New Zealand
AnswerHi Alastair,
When you depress the clutch on most cars, it applies about 400 lbs thrust on the end of the crankshaft and that plus the drag of the clutch release bearing tends to slow the engine a little but should not stall the engine.
Do this first, with a pry bar force the front pulley (don't bend it) towards the rear of the car, then have someone step down on the clutch pedal and push it to the floor while you look with a strong light as to how much the front pulley moved forward. You should not notice hardly any movement at all. Factory specs is .005", which is very difficult to see that little movement.
If this is ok then the crankshaft thrust bearings are ok in the engine so next is the tuning of the engine. The fact that the engine "Runs on" after the key is turned off is a clear indication the engine badly needs to be tuned. The fact of the engine stalling when the clutch is depressed is a second indicator that the engine is out of tune.
If your car was brought to me in a dealership with what you tell me, I would not touch the car unless I could run a compression test and only if it passed the compression test would I proceed. If it failed the compression test, I would first adjust the valve clearance and run a "Wet" compression test. While the plugs were out I would examine them to see if they needed cleaning or replacement. Then check the ignition point gap and timing (set to specs not set to try to make it run better) and last adjust the carburetors. We had a scope so I could quickly and easily check for bad plug wires and coil condition but there are methods to test those without a scope.
I learned early that it is a waste of time to try to do any less then that and it must be done in order, Compression test, Ignition tests and carburetors last.
A good tune up can be done by a DIY (Do It Yourself) person with just a few inexpensive tools and a manual. You don't have to be a "Pro" to do a good tune up.
Howard
