Carburetor Timing

[bigcol]

1951 M38 Serial 11116.

Having difficulty with an apparent advanced timing problem. Crankshaft is at the required properly marked "5 TDC, but distributor cam & rotor at
#1 is not where they are supposed to be at (7 o'clock position).

I'm clear on firing order 1-3-4-2 as per manual. Points are set at .20. Crankshaft is properly marked "5 TDC position.

Where should #1 piston be when it comes to the TDC on compression stroke? How can we best judge this is occuring?

Am I looking at the tech manual (figure 5.4 PG 177) the wrong way in regards to positioning of no.#1?

Col.B

[wesk]

Where should #1 piston be when it comes to the TDC on compression stroke? How can we best judge this is occuring?

#1 piston should be approaching the very top most position in the cylinder on the compression stroke (determined by holding your finger over the #1 plug hole and feeling the compression build up then confirm the timing mark is approaching 5 Deg BTDC)( this is easier to do with a helper who slowly rotates the crank by holding pressure on the generator belts and turning the fan by hand in it's normal rotation).

Am I looking at the tech manual (figure 5.4 PG 177) the wrong way in regards to positioning of no.#1?

No, you are reading it correctly.

Let's go back a bit.

1-The cam has a gear on it that drives the oil pump.
2-The oil pump has an offset slot in it that fits the distributor's offset tab and the oil pump drives the distributor.
3-For the distributor to be installed and indexed correctly the oil pump must first be installed and indexed correctly.
4-Can the distributor function correctly when the pump is not installed and indexed correctly? Yes it can in most cases. However sometimes due to the shape of the large military distributor swivel room can be inadequate for adjusting timing to spec.

So if your engine ran ok with a distributor that will not point at the 7 o'clock position when #1 is 5 Deg BTDC on compression then it was not installed and indexed correctly. You can usually work around this issue by installing the #1 plug wire in the tower that the rotor is pointing at with #1 at 5 Deg BTDC and then install the remaining three wires in their correct order.

Or you can remove the oil pump and follow the directions in the engine manual TM 9-1804A on page 95.

[bigcol]

Wes,

Can't locate the directions you mentioned in my manual as to oil pump. Could you please post article.

Generally speaking how much oil is needed to properly pressurise engine via pump?

Many thanks for your help.

Col

[wesk]

TM 9-1804A on page 95

Go to our downloads page and download the PDF copy of that manual.

http://www.willysmjeeps.com/v2/modules. ... tit&lid=89

Generally speaking how much oil is needed to properly pressurise engine via pump?

Not sure what you are asking for here. The dipstick shows the safe range for your oil level in the sump. Any lower and you risk cavitating the pump.