A couple of problems - overheating - backfire

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izze_8

Junior Member
I have been doing a lot of reading, but I thought I would make new post explaining all my problems, as they might trigger someone to recognize a specific resolution.

1. I think my engine is overheating. When I received the vehicle, it was running with antifreeze. The radiator would boil over after about two miles and make a hellova mess. I drained the antifreeze and flushed the engine about 6 times with water. I am now running the engine with water only. It runs much cooler now. And I can drive it about town. But, the radiator will still overflow when I get back home and shut off the engine. The overflow is much much less then when it was running on antifreeze, but still.... Also, I cannot get the radiator cap to stay on. I get about an 8th of a turn before I cannot turn it any further. And after about a mile of driving I can see that the cap is loose and wobbling around.

2. I get backfire, usually in second and third gear. I have only had my Model A for about 4 weeks now. I found the a clog in the fuel line a week into repairs. I installed a gas tank filter, and an inline filter. Also replaced the fuel lines inside and out. She starts up like a champ now. So I start her up, let her warm up a little, then take her out. I don't know much about the Model A, but it feels like I do not have a whole lot of power. I have to start off really slow, build up speed to hit second, and build up speed slow to hit third. If I try to increase speed to fast (pushing down on the accelerator pedal to hard) I get backfire, and a loss of power. I have to open up the GAV 1/2 to 3/4 turn to give more fuel to prevent backfire. The hotter the engine gets, the more I have to open the GAV. I have not had to open it more then 2 1/2 turns total. And if I kill the engine, I cannot hold out the choke all the way the next time I try to start the engine. I will pull it all the way out, then slowly release it until the engine starts up. If the engine is cold, it starts with the choke pulled all the way out without a problem.

I wonder if the loss of power and backfire is from a bad head gasket? And I wonder if the overheating is from a bad water pump? Mine leaks, but I hear the originals always do. I will be going to a swap meet in a few weeks and hope to find a leakless pump.

I have read up on these issues. But I hope someone can tell me if these issues are related. Or give me some things to try out to diagnose my problems further.

Sorry for such a long post! :)
 
Dear Izze 8,
I had some similar problems when I got my 31 Coupe a few years ago and did not know anything about Model As at that time. So remember the positive side, the more problems you have with her, the more you will be forced to learn about her.
Use a good radiator flush like Simple Green or commercial type radiator flush and follow the directions. I ran mine for a period of time with water only but it caused the inside of my engine to rust a lot so get it flushed out good and then use antifreeze which has anti-rust properties. If repeated flushing does not cool it down then you may have damaged radiator tubes which have been solder closed so take a good look to see if you have any tube damage. My radiator was fine but it just needed to be flushed out several times and runs normal now.
I had the radiator cap problem...it came loose on the road and then pucked the rusty water all over my nice paint job, yuck! The cap only turns 1/8 or less to close but there is no lock dentent so what I did is to make the gasket thicker so, when I turned the cap to close it, there was some resistance to turning...that will keep the cap from self-opening and leaking. I have the fancy bird cap so it may be different if you are running the standard cap but may fix it by the same token.
If your engine runs too hot, you will have backfiring problems...especially if there is unburned fuel getting into the exhaust system as was the case with my Coupe. Sometimes it was expecially exciting when I would shut it off in the grocery store or the auto parts store and a few seconds after turning her off a huge backfire would scare everyone including me out of their wits! Even with my engine leaned out, I occasionally will get a little quiet backfiring when shifting especially if I back off on the accelerator fast.
So have fun trouble shooting and fun learning about what makes her tick! The longer I have my Model A, the more I know and the more I like her. Won't trade her for anything!
 
One more thing. I had the same loss of power problem, very frustrating until I completely dissembled the fuel system and cleaned out a lot of bugs, sawdust and other crud. I had to buy a new filter for the one in the carburetor since it was damaged and full of bug wings and what looked like saw dust. But the biggest problem causing the loss of power and acceleration was that the shut-off valve was almost completely plugged up with gunk. So I had to empty the fuel tank and remove the shut-off valve which is in the cab on my 31 Couple. I couldn't believe that she even ran at all with all that stuff in there. I don't think the prior owner drove her at all with all that junk in the fuel system. So go through the fuel system completely and make it as clean as a whistle and that should keep full fuel flow to fix your loss of power issue.
 
Make sure that your new gas line from the bowl to the carb is not inserted too deeply. The line should only go about 1/8 inch past the Ferell. Should you go much past 1/8 inch you could well be restricting the gas flow to the carb which will cause a backfire.
 
For the loss of power, I would first check the points gap. Too close points gap has a retarding effect on the timing. The book says that the points gap should be .018 to .022 . I set my points at .022. If the initial timing is retarded this will cause overheating. If you are driving with the spark lever retarded it will cause overheating.I crank with the spark lever fully retarded and drive at speed with full advance . As long as enough speed and momentum is maintained to prevent lugging in high gear, you don't need to worry much about the spark. It could also be that you are running too lean. Check the knob on the choke rod. The reproduction choke rods have the knob threaded on. The knob can become loose on the threads and the knob will turn without really adjusting the GAV. A lean mix will cause overheating and backfire. Using water as a coolant was a smart move, it cools much better and leaks less. I use water pump lubricant to quiet my water pump, it also fights rust. Water pump lubricant may hinder cooling a small amount but nothing like antifreeze. Antifreeze works best with a fully pressurized system to keep it in.
 
I also think the timing might be your loss of power and overheating. When the timing pin drops into the cam gear detent, the rear edge of the rotor should be in line with #1 contact in the distributor cap. Remember the rotor turns CCW and all the freeplay should be on the leading side of the rotor.

Original water pumps don't all leak, only the ones not maintained or properly rebuilt. I rebuilt mine exactly as original and never leaked a drop in 10 years. In fact when I rebuilt it the only part that wasn't a good reused original part is the 2 lead packing rings. I did add the locking collar on the front of the pump because that way the same pump is good to go for any engine. Just be sure your pump shaft is smooth and pack grease around the new lead packing rings, and you should have a good leakless water pump. I would use the rear brass bushing with the seal at the rear of it though, as this better keeps the antifreeze out of the grease, and the grease out of the antifreeze.
 
This is all great advice. And is warding off my fears of replacing a head gasket. I have learned so much from this forum and find everyone to be extremely helpful. I will try everything recommended tonight and get back to you all. If there is anything else I could check, please let me know.

Learning a lot here, and having a blast in the process!
 
Searching here for a while and not coming up with a really good image or video to show me how to check the point gap. At first I thought you were talking about the spark plug gap. But now I see the point gap is inside the distributor. But I do not see how to check the gap specifically.
 
welcome. Marco's site has a fool proof way to set the points, and/or do a "search" about timing. What year is your A? Stock rad cap,quail, moto meter??

Paul in CT
 
I should have that information before I posted I guess. But I am still very new to this so I will play the noobie card.

The car is a 30 coupe. I believe it is a stock cap, but recently replaced. I found Marco's site but am still confused on how to set the points. I think I need to do some more reading. If I had to guess right now, "setting" the points is lining up the points so they open/close along with TDC? Or is "setting" the points adjusting the distance when open or closed? Sorry I am so confused about this. I am learning as I go. Still getting the basics of electricity when I started re-wiring the lighting switch last week. Thanks for the patience...
 
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