Cold blooded truck

[truckin 79]

So my 79 is real cold blooded in and out. The truck will srart fine but seems to take at least 10 minutes before it will move. Even then it barely moves just chugs along. I have the exhaust stove pipe set up to direct vacuum. The thermac on air cleaner is wide open as well. Well these 2 things hooked up correctly make a huge difference?
Now to the interior, the truck is a non AC equipped truck. So i can feel heat coming out but not much. Can i put on a stronger blowing fan since it is only a 3 seed switch. I have a 4 core radiator and not sure of temp on thermostat

[tucsonjwt]

To check your choke:

1) Open the hood, remove the cover from the air cleaner.

2) Pump the accelerator a few times, then depress the accelerator all the way to the floor once and remove your foot from the accelerator.

3) Check under to hood to see if the choke valve (aka butterfly valve) in the carburetor is all the way closed. If is not all the way closed when the engine is cold then the choke needs adjusting to make it close all the way.

4) Start the truck. Check under the hood again. The choke valve should be opening as the engine warms up. (If it is below zero outside this can take quite a while.)

5) Once the engine is at normal operating temperature, the choke valve should be all the way open (completely vertical.)

NOTE: I am the only person posting here who has owned several GM carbureted vehicles with all kinds of chokes and never had one work properly
on a consistent basis. For that reason, I have installed a $12 manual choke conversion in all of those vehicles, including my current 83 C20 454. If you have a manual choke you will always know when your choke is open, closed, or partially open. The only time you will be concerned about the choke is if the manual cable works loose and stretches out, then you tighten the cable with the set screw on the bracket.

You may have more than choke trouble but that is the first place to start.

For heater problems, grab on to the heater hoses to make sure that they are warm when the engine is at normal operating temperature. If your heater core is leaking you should be able to pull the carpeting back on the passenger side floor and see coolant under or on the carpet. Also, you might have oily fog on the inside of the windshield. You might have a clogged heater core and no leak, which could block coolant flow.

I have always had adequate heat and blower force with the stock equipment. I live in the 115 degree+ desert heat and have never had more than a stock radiator on my two 454 engines. I have always had normal engine operating temperature with the stock set up. Fan, fan clutch, etc. have also been stock.

Post here your engine size and others here will tell you what temperature thermostat you should have.

[Dead Parrot]

In addition to checking your choke, verify that the exhaust stove pipe valve moves to open when the engine warms up. Forcing full heat through the intake manifold with a hot engine will damage the carb and cause a run rich condition.

You want the THERMAC flap to be closed on a cold engine and open on a hot one.

Noticed you have Colorado location tag. What altitude are you at? If the truck is setup for near sea level and you are at 5000+, your carb is too rich.

Assuming a stock or near stock SBC, your thermostat should be a 195. A lot of folks will put in a 160 trying to fix a cooling issue rather then fix the real problem. The stock SBC wants a 195 and it will make a big difference in the amount of heat.

If you aren't getting much air flow, pull the blower fan and check for critter nests.

[rich weyand]

Couple other things.

The thermac valve should be open when the engine is not running. Once it starts, when cold, the valve should close immediately. After a couple of minutes, it will open part way and stay there as long as ambient air is cold. I can tell when my headers heat up and the thermac starts drawing warm air, because the rough cold idle evens out.

I put an electric fan on mine so the fan would not run until the engine was up to temp. There is some water circulation even with the thermostat closed, and the fan keeps the radiator stone cold.

In the winter, I put a cover over the part of the grill in front of the radiator to kill the ram air you get when moving. I just let the fan provide air. For the cover, I used a mechanic's fender protector from Classic Industries. Cheap. Works.

Finally, I used metal tape (like the HVAC guys use to seal ducts -- they don't actually use duck tape) to seal up the gap between the air box and the defroster Y-tube. There is like a 1/2" gap. Not sure why, but I taped it up.

All this solved the no-heat problem and greatly increased gas mileage.

http://forum.73-87chevytrucks.com/sm...?topic=27239.0

http://forum.73-87chevytrucks.com/sm...?topic=27899.0

[truckin 79]

Well this is what has been done to truck. I rebuilt carb and choke works well and I have a new distributor on truck as well. I have replaced almost every vacuum hose on truck but I do not trust the thermal vacuum switches on truck. I am going to try and hook up exhaust stove pipe and thermac and see how much that will help with cold starts. I might just try thermac first and see how that goes.
On heater inside with all the air gaps in doors and vent windows I figure a stronger fan might help. Any recommendations for a stronger fan for inside truck. I have changed outer door rubber weatherstripping but have not changed door felt weatherstripping around windows or vent window rubbers. I dont drive truck that much in winter but when I do it can be a little cold inside.

[Tom]

I remember as a teen starting my 78 when it was cold with no choke and needing to rev it around 2000rpm for a couple minutes before going anywhere. No way I was gonna put all that performance robbing crap on to make it run better. At least thats where my teen mind was lol.

[akart]

I live in Alaska and I stick some cardboard in front of the radiator, cover up most of if and drive @ 60 below. The other info here is good too. Just a thought....

[truckin 79]

I also do have a brand new heater core and had to put extra foam all around it because the newer aluminum heater cores are shorter than the original. I actually installed carpet in truck as well thinking that would retain more heat then the rubber mat that was in it. Well it looks like my truck is not the norm but the exception in being cold blooded

[friscobob]

I bought a used 67 C10 with a 283, one cold blooded truck, found the heat riser passage was blocked shut with carbon, once opened it ran tons better. Also check that your hear riser valve is working correctly.
Bob

[Shugalou]

If your choke doesn't open feel the choke thermostat to see if it's warm. If it's cold it's likely not working and you should test before purchasing a replacement. I discovered mine stopped working.

[truckin 79]

Yeah choke is working just like it should. Does anyone now where thermac vacuum should hook up to? I have a Chiltons but does not have air cleaner in vacuum diagram. My air cleaner is the type that does not have the air tempature sensor so I imagine it is supposed to hook up to one of these thermal vacuum switches. This is not my truck but looks exactly like the 2 TVS switches on my truck. The orange one in the thermostat housing and the purple one in the manifold right below it. Whosever picture this was I hope you don't mind I borrowed it

[rich weyand]

Originally Posted by truckin 79

... My air cleaner is the type that does not have the air tempature sensor so I imagine it is supposed to hook up to one of these thermal vacuum switches....

That's weird. I couldn't find the 1979 diagram, but the 1980 K5 350 sbc diagram is here:
http://67-72chevytrucks.com/vboard/s...d.php?t=671167

Note air cleaner has thermostatic switch. And my 1978 has the thermostatic switch.

Are you sure that is the right air cleaner? Does it have the spot for the thermostatic switch? Can you get one that does, like from a yard?

I think the thermostatic vacuum switch is the easiest solution.

[LT7A]

Didn't see this mentioned and you may have already checked it. But my first thought would be to make sure the thermostat isn't stuck open.