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74 running after 18 years...but too hot?

chevyf16

Jr. Member
Joined
Aug 27, 2009
Messages
58
Loc.
Alexandria, VA
Have a 74 351W with stock 2v carb. Rebuilt carb and did some rewiring, and she's running again after 18 years in a barn! I've only let it run for about 5 minutes at a time because the exhaust manifolds are smoking so much! It looks like it's going to catch fire, so I cant tell if the thermostat/cooling system is working or not.

3 questions:
Can you see (in the radiator) if the water pump is working?
Can you tell when the thermostat opens?
and, why are the manifolds smoking so much?
 

Broncobowsher

Total hack
Joined
Jun 4, 2002
Messages
34,834
You can tell the waterpump works when the thermostat opens and you see water moving
You can tell the thermostat is opening because you can see water moving in the radiator and you will also feel the upper hose get hot.
The exhaust manifolds are probably smoking so much because the valve cover gaskets dried out and are drooling oil down on the exhaust. Combine that with 18 years of dust accumulated and burning off. Exhaust manifolds get very hot very fast. Well over 500° at idle in a few minutes of running. I would expect them to smoke. They smoke after every time I take them off and put them on, burning off the oils from my hands. Also when I spill a little oil on them from being sloppy during an oil change.

You will know if it is overheating on you. It will start boiling, bubbling, steaming coolant at you with the cap off. Not to be confused with a little surging, rise and fall, burping of coolant as it runs. Even with a stuck thermostat it will really let you know if it is overheating. Especially with the cap off.
 
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chevyf16

chevyf16

Jr. Member
Joined
Aug 27, 2009
Messages
58
Loc.
Alexandria, VA
I'm not the smartest guy...

The upper radiator hose is on the opposite side of the radiator from the cap. Can you still see the water moving in the radiator when the thermostat opens?
 

DirtDonk

Contributor
Bronco Guru
Joined
Nov 3, 2003
Messages
47,345
Yes, if the pump is pumping, you'll see coolant flowing out of the upper tubes right below the fill neck.
The more powerful the pump, the stronger the flow. You'll actually see the water level drop slightly when the upper tubes start spitting out, because it's pulling more coolant through the engine.

Leave the cap off though, so you don't get a surprise if it's already built up pressure inside. With it off, everything still works and it doesn't build up pressure.
If it's full, you might get some burping and sloshing at first, so don't get right down there in the fill neck until it's done it's thing (a few minutes).
Oh, and wear glasses!!!!!

Another thing a newly re-started engine might need is a little burping anyway. Air pockets can get trapped inside the cavities and promote uneven cooling/heating for awhile. If the heater is hooked up, make sure to pull the heat control knob all the way out so coolant flows through the heater core.

Maybe do a quick check/clean of the exhaust manifolds to make sure there is not a lot of oil or debris collected there. A little will burn off fairly quickly, but a lot might smoke for days!

What does the dash gauge say? You do have it hooked up, right? You can run it up to over 200° and still be in the "normal" range, but make sure the coolant level is always decent. Extremely low coolant levels can give you erratic gauge readings.

Have fun.

Paul
 

DirtDonk

Contributor
Bronco Guru
Joined
Nov 3, 2003
Messages
47,345
Oh, and the hose/cap orientation is on purpose. In the old days, when overheating, boil-overs, and other such maladies were commonplace, they found that the inlet hose being too close to the filler neck was not a good idea. Not only did it add a level of excitement for whoever was working on things and trying to take a cap off while the engine was running, but it also seemed to actually promote boil-overs. Especially when the radiator was starting to get clogged up.

Paul
 

jw0747

Contributor
Bronco Guru
Joined
Nov 22, 2006
Messages
2,434
Loc.
San Antonio, TX
my exhaust manifolds always smoke after sex. can't seem to break the habit. ;D

sorry, couldn't resist.
 
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chevyf16

chevyf16

Jr. Member
Joined
Aug 27, 2009
Messages
58
Loc.
Alexandria, VA
Thanks guys...I'll get out there this weekend and let it heat up to see if it's working... (then, maybe I'll start smoking!)
 

IL_BRONC

New Member
Joined
Sep 30, 2010
Messages
41
Loc.
Central IL
I can't help but recomend changing the thermostat regardless. It is in my opinion a wear item. Considering the price and effort involved with changing it, it would be cheap easy insurance against future overheating issues.

Although it just sounds like dirty manifolds is your current problem.
 
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