newbie questions

MrTube

MrTube

Well-known member
Hi, I'm pretty new to the "A" and have some basic questions.

I am in charge of maintaining my bosses 1931 model A truck and have run into some things i'm not 100% sure of. I recently installed a new carburetor on it which ran great until the float sunk (bad luck). New cap\distributor. new plugs and wires.

Truck runs great, idles great however we are having 3 issues with it.

We have a 20A fuse installed between the wire harness and the battery which occasionally blows when you shut the truck off. After thinking about it I have to assume this indicates a possible problem with the generator cut-out. The fuse never blows when the truck is running.

We keep using water. around a gallon over 30-40 minutes of slow driving on a 90F day. Not sure if this is normal? No visible leaks anywhere. I'm fearing head gasket but have not seen any steam from exhaust and oil is clean.

Friday the truck was driven pretty hard. We had it on a major highway here in new jersey on a 85F day pretty much full throttle for nearly an hour. truck was doing around 50MPH give or take depending on the hills and we overheated. I'm thinking this was normal and we should've been a little easier on the poor thing.

Any answers\tips are 100% welcome.
 
Hey Mr. Tube, Try not filling the radiator above the baffles, may be sneaking out the overflow tube while you are drivein. Don`t know but 50 on stock engine is probably pushin it some. Monte
 
if your not losing water on the ground from either a leak or overflow it has to be burning it out the exhaust. poss cracked head ,warped or head gasket. i dont know if your speedometer is accurate but i would not be driving my car around full throttle even on a cool day. am sure other wll chime in with some opinions
 
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If you are using/loosing a gallon of water in 30-40 minutes, it is not normal overflow. You should not, however fill the radiator to the top. As was mentioned, fill it to just below the baffle and see if you continue to loose water. If so it is probably a leaking gasket or a cracked head or block. Good luck! Don/WI
 
Water in the oil? Probably not if you got it really hot, but check the dipstick and the oil fill tube cap. If you find a lot of creamy streaks and foamy gunk ...
... No? Maybe the water is being sucked into a cylinder. Check for that by pulling the spark plugs. One or more that are scoured white will show that you have a problem that's letting the water drain out the tailpipe. You will need to correct that right away. It is very difficult for an engine to compress water!
 
Have been checking the dipstick and cap. Oil still looks clean.
Will check spark plugs again but they all looked about perfect Friday evening. No steam from exhaust or antifreeze smell that I can tell.

Will check with the boss to confirm he is not filling past the baffle. Might just be poor communication.
 
If there is no baffle installed in the radiator the water pump will continue to pump water sufficient for it to escape out the overfow tube. Ultimately the water supply will be reduced to a point where the engine will over heat. Put an extension on the overflow tube to bring it as near to the top of the filler neck as possible.
 
I can drive my '31 RDPU with 3.54 gears at 55 mph all day. What kind of truck are you talking about? pickup? "big" truck? any idea about the rear end ratio?

Charlie Stephens
 
its a 31 closed cab pickup with the widebed. No idea on what gears are in it. Its certainly not a big truck like the AA or anything.

I've got a feeling it overheated due to running low on water. I hope the chances of a cracked block are pretty low??

I was wondering about changing gears actually. Does the stock engine have enough power to cope with the 3.54 gears?
 
I like my '31 RDPU with 3.54 gears and it is about the same weight as yours. I have a stock B engine with a Model A police head and a Model A carburetor. I am probably slightly HP more than stock. Post your location and ask about someone good with rebuilding rear ends.

Charlie Stephens
 
Hi Mr. Tube, Try a 30 amp fuse. Most of us use that size on a one-fuse-only Model A circuit. If it continues to blow, you'll need some investigative work. Some A's overheat because the water circulates too fast! A smaller crank pulley is used by some, others find that a thermostat actually slows the circulation down by just the right amount. In addition, keeping the engine at the right temperature (160deg) will help it to run right all the time. Good Luck!
 
What MAG says is worth investigating. No Baffle = water loss. One way around that problem is to install a thermostat in the upper hose, which acts like a baffle. The over flow tube should be at the back of the neck and pretty high up. To rule out or in a leaky head gasket, there are kits available that attach to the radiator neck and test for combustion gases in the radiator. Also check the timing. A retarded spark contributes to overheating. The advance lever should be at 3/4 at 50 MPH. If it continues to overheat with a thermostat, adjusted overflow tube, correct timing and tests free of combustion gas in the radiator, odds are its a radiator problem. Marco has a few hints on his website:

http://www.abarnyard.com/workshop/inlet-1.htm

regarding the fuse, its probably a repop cutout sticking. Test it with a continuity tester when its off.
 
If it is an old, original radiator, it may have quite a few totally plugged tubes. If that is the case, a few of the other problems mentioned such as retarded timing could easily make it overheat some. But you are also losing some serious water so be sure it is not going out the overflow tube while you are driving.
 
I believe timing should be about right. It idles best with the timing lever around 3/4 of the way advanced. If you go further it gets rough. We pull it all the way down when cruising and it definitely likes it. When I first started working on the truck someone had the timing so far off it wouldn't even run fully retarded. When I set it after doing some reading I went a little more advanced then stock.

I *think* I remember seeing a baffle in the top of the radiator. I couldn't see down into it. I also believe the overflow tube was just under the cap.


pat in Santa Cruz : why 3/4 of the way advanced at 50? ours definitely seems happier fully advanced at any rpm and load above 1K.
 
Check your timing again.

distrib-2.jpg
 
Bob A. Since I feel my timing is correctly set can you tell me why you think it may be off?

I will double check it with the truck comes back. The hardest part for me was the backlash in the gear. I set it a few times and had it way too advanced just due to the pressure I put against the gear with the cam screw.

I just want a little more information on exactly what i'm looking for. How the timing lever should act at idle would be good. Should it idle rough full advance, should i be able to run full advance at idle without it getting rough and so on.
 
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MrTube said:
I believe timing should be about right. It idles best with the timing lever around 3/4 of the way advanced. If you go further it gets rough. We pull it all the way down when cruising and it definitely likes it. When I first started working on the truck someone had the timing so far off it wouldn't even run fully retarded. When I set it after doing some reading I went a little more advanced then stock.

pat in Santa Cruz : why 3/4 of the way advanced at 50? ours definitely seems happier fully advanced at any rpm and load above 1K.
Click to expand...

Hi Mr. Tube, The basic "set" of your timing is too far retarded. At idle, the best idle behaviour is with the timing lever about 3 clicks down. Hill climbing, about halfway down. Cruising at 45 or better? 3/4 of the way down. Since you say that currently your best idle behaviour is 3/4 way down, your initial timing (lever all the way up) is too far retarded. By the way, this can definitely be the source of your overheating problem. (It will also screw-up your valves and burn valve seats!)
 
Chris in CT : See now thats the kind of timing advance I would expect. But the instructions to start a Model A threw me off. They say once it starts to pull the timing lever all the way down and leave it there which lead me to believe it should idle fine full advanced.


Interesting. This also tells me I wasn't as far off due to backlash as I had thought the first try. Why do all of the "to start a model A" instructions tell you either full advance or 3/4 advance after starting?
 
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Nine O'Clock for the spark lever is good for around town, and seven o'clock for highway conditions.
What is your performance?
My guideline is being able to wind second gear to thirty MPH with the spark down is about right, if not a bit conservative.
How does it feel at, say 45 MPH in third when you drop the lever to seven o'clock? Does the engine scream for more advance, or is it content at seven o'clock?

The water issue is generally a result of the pump pushing more coolant than the radiator can process, the balance either going over the top or out the overflow. Try just topping the tubes and see if it stays in at those levels. Radiators often "Gum Up" from overgreasing the aft "zerk" on the water pump, which should only be greased by what you can push in from your finger with the "zerk" removed.

I hope this proves helpful !
Good luck !
 
I just looked at my "MODEL "A" INSTRUCTION BOOK," by Ford Motor Company, for the 1931 car and it says...
"After the engine is started, advance the spark lever about half way down the quadrant."

That is what I would call the Nine O'Clock position.

Do you have this manual?
Its about eight dollars, (reprint) from the vendors.
 
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