Cold Running Issue

[AdirondackM37]

My '54 M-37 has always been cold blooded. While it fires up immediately on the first crank without any choke, it has to idle for at least ten minutes before I can give it gas without stalling. With colder temps now it seems even more reluctant to idle. Using even a little choke seems to flood it. Where should I start looking? Fuel pump pressure? Vac leak? Carb adjustment? Thanks in advance for any advice.

[NAM VET]

is your air/fuel intake heater turned correctly, the triangular slotted, flap-thing below the carb which pre-heats the incoming charge. It is just below the carb, where the two manifolds are bolted together, allows for heating the charge, or turning the pre-heat off for summer use. Here, in this pic, it is the swinging "arm" thing with the brass nut, turn the flap vertically to heat, and up for summer running. In this pic, mine is turned off. Hal
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[PoW]

There is one and only one type of thermostat for the M37. I've never seen one at an auto parts store.

It is very large, compared to those sold today, and without it the water flow and resultant operating temp will never be achieved.

Make sure to check the one you have, and if it doesn't match the image in the TM, get the right one.

And the advice about the Summer-Winter heat riser adjustment is very important, too.

PoW

[John Mc]

is your air/fuel intake heater turned correctly, the triangular slotted, flap-thing below the carb which pre-heats the incoming charge. It is just below the carb, where the two manifolds are bolted together, allows for heating the charge, or turning the pre-heat off for summer use. Here, in this pic, it is the swinging "arm" thing with the brass nut, turn the flap vertically to heat, and up for summer running. In this pic, mine is turned off. Hal
[url=https://postimg.cc/62k2ycHH][img]h ... .jpg[/img][/url]

Hal -
The heat riser is the part in the lower right corner of your photo with the curved slot in it, right?

If so, from your description it would appear to be ON, not off... since the tab is flipped down (vertical). Or am I misunderstanding your description?

[Murf]

There is one and only one type of thermostat for the M37. I've never seen one at an auto parts store.

It is very large, compared to those sold today, and without it the water flow and resultant operating temp will never be achieved.

Make sure to check the one you have, and if it doesn't match the image in the TM, get the right one.

And the advice about the Summer-Winter heat riser adjustment is very important, too.

PoW

AND with regards to the above. IF you have the hot water personnel heater you need to have the t-stat that is included with that kit. I don't know the heat range differences off-hand but the manual says they need to changed out.

[John Mc]

If I remember correctly, stock thermostat is 160˚F, the one used with the hot water heater is 180˚F (but I'm far from an expert in these things).

[NAM VET]

John, thanks for noting my error in my post and pic of the tunable intake heater flap. Sure enough, I was wrong, I went out and checked my TM, and it is clear that the plate in the intake is symmetrical with the slot in the swing arm. So, slot vertical is open, for cold weather, turn the swing plate slot horizontal, it closes it for summer. Means I drove all summer in the SC heat with my intake heating my fuel mixture! Ran fine, thought. Be sure to use a brass nut on the shaft, to avoid seizing on the shaft.

NV

[John Mc]

John, thanks for noting my error in my post and pic of the tunable intake heater flap. Sure enough, I was wrong, I went out and checked my TM, and it is clear that the plate in the intake is symmetrical with the slot in the swing arm. So, slot vertical is open, for cold weather, turn the swing plate slot horizontal, it closes it for summer. Means I drove all summer in the SC heat with my intake heating my fuel mixture! Ran fine, thought. Be sure to use a brass nut on the shaft, to avoid seizing on the shaft.

NV

I was just going from how I understood your description. I could not remember myself. When I swapped in the 251 engine, it had an automatic adjustment on it, so I don't have to fiddle with it as the seasons change. (I'm hoping that the fact that it moves on it's own regularly might help keep it from freezing up.)

By the way - where did you find the description of this system in the TM? I have not been able to find it.

[NAM VET]

picture and discussion of the summer/winter intake flap is on page 2-86 in TM 9-2320-212-20. "Organizational Maintenance Manual for ...." By the way -10 manuals are for the operator, -20 are Organization maintenance, ie, a company''s maintenance section, and so forth.

In my picture posted earlier, my flap is horizontal, ie, for summer driving. NV

[John Mc]

Well, that explains why I could not find it. I assumed something as simple as this would be in TM 9-2320-212-10 (or perhaps in in TM 9-8030).

The description is interesting: "Set plate at SUMMER position for ambient temperatures consistently above 60˚F and at WINTER position for ambient temperatures consistently below 30˚F."

So what do you do in the in-between times when temperatures are in the 30-60˚F range? Just leave it wherever it was set until temperatures swing enough to consistently be above or below the noted set points? On my old engine, the control was set halfway, and corroded in place. I was afraid to adjust it since it was locked so tight I thought I would break something.

[NAM VET]

I had my flap set in the winter position all this past hot SC summer, and my truck drove fine, even on long trips. It may help a lot for really cold weather starting and driving. A cooler air/fuel charge does make a little more power. I think I will check my idle screw setting when I get around to it. NV