To know when you are at top dead center, remember that on a four cylinder
engine, the middle two cylinders (2 and 3) come up at the same time as do
the outer two cylinders (1,4). I roll the engine until a set of valves
"rock." By this I mean that you see one valve closing and the other valve
opening so both valves are moving at the same time. The middle of this
will be very close to top dead center of the non-power stroke so the other
cylinder up will be at TDC on the power stroke. So adjust 1 when 4 rocks,
etc.
For power loss at high load, I would first think ignition, then mixture.
Check the gap of the points and plugs. Check the distributor for wobble as
this can cause this symptom. Make sure your vacuum advance moves. Check
your vacuum lines, etc for leaks. If adjusting all of these to spec and
making sure that they are in good shape doesn't help, I would try running
the car for a few seconds under the high load condition and shut it down.
Pull a the plugs and look at them. Are they all the same? They should be
medium to dark brown. If they are too light, make the mixture richer. Too
dark, lean it out a tad and see if this helps. If your carbs are worn and
you adjust the mixture at no load using the lift the dashpot routine, it is
not unheard of for the engine to run lean under load. This is a
potentially damaging situation so you should get it fixed as soon as
possible.
Another thing that you could check is your exhaust. If you have a
restriction there your engine would refuse to pull.
If everything looks OK and none of the above help, I would just start
replacing every part in the ignition circuit starting with the cheapest
part and working my way up. It can't hurt anything.
Remember the cardinal rule of troubleshooting- ONLY CHANGE ONE THING AT A
TIME! If the change doesn't help, go back to original (if it makes sense
such as fuel mixture) and try something else.
Regards,
Bill Eastman
61 MGA which lacks power at top end but only when compared to over powered
brute machines such as the MGB
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