Timing a Farmall H Tractor

Picklesmith · Apr 26, 2012

A quick question about timing a 1951 Farmall H tractor: When the two notches on the fly wheel are generally aligned with the pointer on the front of the engine, does that indicate that the piston in the #1 cylindar is at top dead center (TDC)?

SadFarmall · Apr 26, 2012

Yes, but not necessarily on the compression stroke, which is what matters. The motor is at top dead centre on Number 1 or Number 4 cylinder when the first of the two close notches is in line with the timing pointer. If the magneto is already fitted and approximately correctly timed, you will know if you are at TDC for Number 1 cylinder, because the contact on the rotor disc will be pointing at the lead in the distributor cap for Number 1 cylinder. If not, rotate the motor through 360 degrees.

If the magneto has been removed, then you need to check which cylinder is on the compression stroke by other means. The book recommends removing Number 1 spark plug and cranking the engine (you need two people for this) until pressure is felt. This shows Number 1 is on the compression stroke. Otherwise, remove the rocker cover and check that both valves are closed on Number 1 cylinder at TDC.

If you crank the engine, you should ground the magneto to avoid accidental starting or a nasty electric shock from one of the HT leads.
SadFarmall

Bill in NJ · Apr 26, 2012

Close. But it does not mean the cylinder is at the top of 'compression' stroke. It could be at the top of 'exhaust' stroke. Best way to tell if piston is at TDC is to remove the number one spark plug, put a something like a drinking straw in the cylinder and watch as you turn the engine over slowly. When the item you have in the cylinder stops rising you are at TDC. However you might not be at firing point. You might be at the top of the exhaust stroke. To check that, remove the valve cover and assure that both valves of number one cylinder are closed.

John G. Hasler · Apr 26, 2012

> To check that, remove the valve cover and assure
> that both valves of number one cylinder are
> closed.

Or put your thumb over the plug opening and turn the engine until you feel pressure.

El Toro · Apr 26, 2012

Remove the sparkplug near the radiator and bring that piston to TDC on the compression stroke. Hold your thumb over the plug hole while a helper slowly cranks the engine until you feel pressure. Once you feel pressure drop a long plastic straw on top of the piston then you watch
the straw rise while the helper cranks the engine. When the straw quits rising the No1 piston should be at TDC on the compression stroke
and the timing marks should be aligned with the pointer. The rotor should also be pointing to the No1 plug tower. Hal

SadFarmall · Apr 26, 2012

If you put your thumb over the spark plug hole and feel pressure, then you really only need to crank the motor until the timing point and notch are aligned unless you suspect the pulley has been fitted incorrectly.
SadFarmall

Timing a Farmall H Tractor

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