I must be doing something wrong

DrinkMan

DrinkMan

Member
I'm getting confused over my working on my Model A (late '28) and the engine. When I got the car, it would only go 25 mph and backfire. My wife and I have been slowly going over everything to fix it. But have stalled in our efforts to make it a reliable driver.

Thus far:

  • Ignition system needed a lot of work - problems with getting spark. Turned out wire from pop-out ignition switch was bad inside the cable. Decided that we did not need the pop-out style and put a new style switch and cable.
  • The evil wire from lower plate to upper plate gave me fits. Replaced with the modern points per Les Andrews book.
  • Carburetor was not in good shape. We rebuilt it (that was actually a very fun project because I've rebuilt many a Solex, countless Webers, and even a Holley, this was my first Zenith and my wife got to do most of the work and we made it a fun project for the two of us).
  • Checked compression - 50 psi cold, 65 psi hot. Very little variation from cylinder to cylinder.
  • Way too much rotational play in the distributor cam - almost 90 degrees (no side-to-side). Found the lock washer missing. Still more backlash than I would like - almost 45 degrees play. Very hard to get the timing right but finally got that light to come on consistently at about 2 notches on the lever.
  • Adjusted carburetor per Les' book.
  • Other things that were needed - water pump, cooling system flush (with vinegar per this website). Radiator is evenly hot after a drive.
  • Note - new distributor cap, rotor, coil, coil wire.
Some pictures:
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Now - our end result: Easily climbs a local small hill accelerating at 35 mph (prior to this work, it struggled up that same hill at 10 mph), runs smooth at almost 40 mph. Never backfires. BUT - that is about it. It seems to top out at 42 mph even with the timing lever all the way down. And after only 5-10 miles, water starts coming out of the radiator overflow and then steam hissing. And just like another thread I read here, I can't restart it after 15 minutes, I have to wait about 40 minutes (vapor lock?).

I'm not looking for a high speed car - I have plenty of those. I just want to be confident to drive it to a car show 20-30 miles away without fearing overheating or breaking down. I'd also like to be able to drive it 45 mph for a long time and maybe a short distance at 55. Are my expectations too high and what have I missed. I feel rather embarrassed that this simple little car has me more stumped than any of my other cars. I'm "The Guy" that others come to help troubleshoot their car.

Where else should I look?
 
I would guess you have your timing too retarded. Especially with your comment about too much backlash and your overheating problem. Do a search on this site for Purdy Swoft or Tom Wesenberg and dig out their posts on timing the Model A. In particular, Purdy has posted numerous times about the process of setting timing taking backlash into account.
 
X2 on the ignition still being set too retarded. If fully retarded you are BTDC then you are not getting full advance.

Also...physically check that the throttle pedal can fully open the carb throttle. Mine was hitting a bolt and was only letting the throttle open about 3/4 full. Fixed the clearance problem and magically got more speed. ;-)
 
Here is one of Purdy's posts on timing. Once I wrapped my brain around it, I finally got my timing set right and could not believe the pep and power my Model A had:


When the engine has to turn to catch up the backlash before the distributor shaft will turn, the timing will always be retarded.. Most are running retarded to some degree because of confusing timing instructions. Most get pissed when I try to explain this... To put it as simple as I can, when the points cam is tightened, all of the backlash MUST be in the counterclockwise direction or the timing will be retarded . The points can be set at any time without loosening and moving the points cam off the sweet spot.. The sweet spot is when the timing pin drops in place, the trailing edge of the rotor tip must point at the number one contact in the distributor cap body . Forget all the BS about the spark lever and the confusion of trying to do too many things at one time. Its always best to just set the points first. Then set the rotor tip pointing correctly at the sweet spot with NO clockwise backlash when the cam screw is tightened and then don't mess with the cam screw again. Factory spec . for points gap is anywhere from .018 to .022 and it will run pretty good on any of those settings. It is said to be ideal for the points to be just rerady to open, yes, just ready . If you need to check when the points are just ready toi open, push the spark lever all the way up and take a look. Points gap will control how quick that the points open or close. More gap opens quicker or advances . Less gap causes the points to open slower or retards. Most like a points gap around .020 . I prefer more gap that advances the timing to the max. In other words I set mine at .022 . Maximum advance gives quick, crisp throttle response and pep. I say, to hell with retarded timing !!! Timing knock and bucking at low speed can be avoided by slightly retarding the spark lever when it begins to occur . The model A is the simplest car ever to set the timing on . If a person is trying to get by with the so called modern points, they will continue to have problems of one kind or another untill they change back to the simple to adjust original points setup .
 
Regardless of what Les Andrews shows, most folks here on the Barn that are Model A experts do like or use the modern points. I for one would suggest you go back to the original style points and then re-time per Purdy's post above. It sure sounds retarded to me also; a decent running Model A should easily run at 45 and higher.
 
I would install a thermostat to help keep the coolant in the system, rather than going out the overflow tube. Quicker warmups are also better for the engine.

If timing is right, you should never have to move the spark lever down more than 3/4.
 
I agree with the timing being late.

I'm one of the few that doesn't have an issue with using one of the newer modern upper plates as long as you use quality points and condenser. The good points and condensers are getting hard to come by and are expensive.

That said, the lash needs to be taken out when setting the timing. If the lash is too much like yours seems to be, then I'd recommend removing the distributor drive shaft and look for excessive wear in the shafts and drive gear.

Once the timing is set correctly, if the problem persists, try loosening the fuel cap. From the OP it seems there may be a fuel delivery issue.

If these don't fix it, let us know. We'll get it fixed.
 
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I had a 29 cp that I did everything to stop it from over heating. the only thing that worked for me was putting a pencil down the over flow tube in the radiator, I know its not a approved fix but it works. it seems the water moves to fast to stay in the rad. going up a hill would empty the rad. then it would over heat no more over heating after that, only my opinion for what its worth. my rad was new, water pump new, car would fly 55-60 no problem.
 
Haven't seen mention of the condenser, this little chap can have you chasing your tail. I think this as you said it went fine, and now it's playing up.
But do go through that timing instructions above.
Good luck,
Martin.
 
The thing that catches my eye here is "45 degrees" of dist cam rotation. If I am reading it correctly, somewhere between the camshaft and the distributor is a bunch of wear. Correct ignition timing would be impossible. This problem needs to be corrected first.
Again, perhaps I am reading it wrong.
 
If the freeplay is kept to the leading side of the cam rotation (as it would be while running) the timing should be able to be set correctly, but that much freeplay does need to be fixed, or you might be fixing it on the side of the road.
 
Thanks all for the information. Looks like a consensus. I'm going to attack the timing again on Saturday and while I'm at it - make sure the throttle has full travel. Luckily I'm only about 25 minutes from Mike's so getting a thermostat is fast and easy (and cheap). When done, I'll post results. (and we've discussed the thought of getting a new distributor upper shaft)
 
Here is one not mentioned. If the ferrule on the end of the fuel line going into the carb is set too far from the end of the tube, it can let the tube go in too deep and hit the filter. That means that all of your fuel has to go though that little patch of filter. Easy to check. We had this problem in our club.
On you overheating, I am pretty sure your radiator is plugged up. They all are to different degrees.
Also, make sure those head bolts are tight. If combustion gases gets into the water jacket, that will cause things to get pretty hot.
 
As said in #3, check your throttle linkage. Mine was hitting the fly wheel housing and couldn't fully open the throttle, and I couldn't get full power. Fixed mine by removing the assembly, heating it at the appropriate spot and bending the arm a little.
 
I know my wagon has the 4:11 gears in the back for good low speed torque but it's not the best choice of rear end if you do want to go 50mph or more.
If your car is revving high when you are around your top end of 42 then another possibility could be that you have a low gear in the back.
 
First of all I would like to to propose marriage to your wife. We could duel over her, I am quite a good shot, I must add. At this point timing being retarded is the problem as it seems all the guys agree to, My a buzzes around at 50 + for miles at a time without any problem and runs up most hills in third gear, like a scared rabbit. I hope all this overheating has not caused the head gasket to blow!! That's a very distinct possibility at this stage of the game , I would suggest a block exhaust gas check. Go back a few days it's on an older post. You could get the timing issue fixed and still have a problem with a leaking head gasket. Good luck and send my love to that wonderful woman you have tell her I'm jealous. Frank pkny
 
DrinkMan said:
  • Ignition system needed a lot of work - problems with getting spark. Turned out wire from pop-out ignition switch was bad inside the cable. Decided that we did not need the pop-out style and put a new style switch and cable.

    They sell a cable that looks like an original cable.


    .
  • Carburetor was not in good shape. We rebuilt it (that was actually a very fun project because I've rebuilt many a Solex, countless Webers, and even a Holley, this was my first Zenith and my wife got to do most of the work and we made it a fun project for the two of us).

    Did you flow test the jets or buy tested jets? Did you remove the throttle linkage and see if the throttle plate still continure to move in the open position with the linkage removed?

  • Checked compression - 50 psi cold, 65 psi hot. Very little variation from cylinder to cylinder.

    That's fine!
  • Way too much rotational play in the distributor cam - almost 90 degrees (no side-to-side). Found the lock washer missing. Still more backlash than I would like - almost 45 degrees play. Very hard to get the timing right but finally got that light to come on consistently at about 2 notches on the lever.

    45 degrees of play is still way too much you need to inspect the dist. shaft ends that go into the engine.
  • Adjusted carburetor per Les' book.
  • Other things that were needed - water pump, cooling system flush (with vinegar per this website). Radiator is evenly hot after a drive.
  • Note - new distributor cap, rotor, coil, coil wire.

I see nothing about fuel flow to the carb. possible blockage, do you have an aux filter in line.

And after only 5-10 miles, water starts coming out of the radiator overflow and then steam hissing.

Does it have a thermostat?

Are my expectations too high ....

Not at all!!
Click to expand...

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