Sudden rough running, out of ideas

[ronn]

Have you tried replacing your carburetor with another working carburetor?


easy fix that you should do immed.

[alexiskai]

That would be an easy fix... if I had a $500 working carburetor sitting around that nobody was using.

[Ernie Vitucci]

Good afternoon...You might also wish to check to see if the nuts on the back of your amp meter and on your ignition switch are snug...if loose, a miss can occur and the spark from the loose wire can short to the gas tank. Snug things up and put some tape on the fuel tank so the spark can't jump. Also if you have the original pop out ignition, wiggle the cable when the engine is running and see if it runs rough or quits. Pop-outs can short to the inside of the covering cable...also just patiently check all of your clamped connections to see if one has worked loose. Look carefully at the distributor body for a crack...if you run the car at night, you might see a spark escaping from a crack in the body...it happened to me 40 some years ago...it made me say bad words as I had to drive from Newport Beach to Santa Ana to get a new one in those days...damn near did not make it. However the new/used/old stock distributor fixed the problem...also a little holly water on the radiator cap can't hurt. Ernie in Arizona

[BILL WILLIAMSON]

Is there a stripped kotter key, somewhere????
Bill Curious

[alexiskai]

Status update: I re-torqued the head and that brought cylinder #2 up to around 48-50 psi. This seems acceptable to me under the circumstances and makes me not want to go to the trouble of replacing the head gasket or re-doing the valves unless there's other symptoms such as oil in the coolant, exhaust leaks, etc.

I've purchased a new condenser and have almost finished getting the distributor back together and re-timed, I'll report on that soon. I've also gone ahead and ordered a rebuilt Zenith carb from Bert's. There were several factors: the current rough running problem, the fact that I've never been able to get the GAV to less than 1/2 turn, and the fact that it leaks gas. They are 1-2 weeks behind in road-testing their carbs, so that will have to wait a bit.

Thanks to Jacksonlll for your suggestion to retorque the head.

[heneste]

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When you check the distributor cap carbon point, don't forget to check the gap on the rotor itself and make sure there's no slop in the distributor shaft. If those are set to wrong gap or the shaft wiggles, you'll get an improper arc to the spark plugs and could cause weak firing on the cylinders as well.

[30 Closed Cab PU]

Originally Posted by alexiskai

Status update: I re-torqued the head and that brought cylinder #2 up to around 48-50 psi. This seems acceptable to me under the circumstances and makes me not want to go to the trouble of replacing the head gasket or re-doing the valves unless there's other symptoms such as oil in the coolant, exhaust leaks, etc.

I've purchased a new condenser and have almost finished getting the distributor back together and re-timed, I'll report on that soon. I've also gone ahead and ordered a rebuilt Zenith carb from Bert's. There were several factors: the current rough running problem, the fact that I've never been able to get the GAV to less than 1/2 turn, and the fact that it leaks gas. They are 1-2 weeks behind in road-testing their carbs, so that will have to wait a bit.

Thanks to Jacksonlll for your suggestion to retorque the head.

I have a carb on order from Berts too, was thinking about giving them a call to see what up. Guess I know why now. Just have to be patient.

[LeRoiGross]

I had my ammeter jumping around one time and traced it to the wire attached to the starter switch which carries power to everything. The nut was finger tight, not wrench tight. If you have a fuse at that point it may have a poor connection too.

[larrys40]

Originally Posted by Bob C

(Modern distributor plates installed last month, older coil)


Did you use the wireless upper and lower plates??


Bob

My bet is that is the problem . Get those junk plates out of there . I had two roadsters in my shop Saturday and both of them had that issue. Fixed with pigtail plates right and problems solved.
Larry shepard

[alexiskai]

Originally Posted by 30 Closed Cab PU

I have a carb on order from Berts too, was thinking about giving them a call to see what up. Guess I know why now. Just have to be patient.

Just talked to them now, he says they have six carbs ready to road test and will do that over the weekend, so they should ship out early next week.

[alexiskai]

Originally Posted by larrys40

My bet is that is the problem . Get those junk plates out of there . I had two roadsters in my shop Saturday and both of them had that issue. Fixed with pigtail plates right and problems solved.
Larry shepard

I do have new upper and lower plates on order along with that carb from Bert's.

[alexiskai]

An update! I replaced the upper and lower distributor plates with the Bert's (modern) plates. I have to say, the build quality on these plates is excellent. Very sturdy, good materials. Highly recommended.

The good news: It starts! And runs. Very smooth. Also I can turn the GAV down to 1/8 open.
The bad news: It stalls if the throttle lever goes above 3 o'clock or if I accelerate beyond a moderate tempo.

I think all signs point to the carburetor at this point. Thoughts? I have the new one from Bert's but haven't installed it yet.

[30 Closed Cab PU]

No opinion. But am planning on installing a new Bert's carb next week. ran into some other things to resolve 1st. Please review/let us know how yours works.


Easy to do, perhaps just swap the in teh new carb and see if it solves your issue

[Will N]

You should try opening the GAV more than and 1/8 of a turn, and then try idling it down and accelerating. The GAV controls the amount of fuel in the carb well from which the idle and the cap jets draw their fuel. With the GAV shut down like that, you may be starving for fuel.

[30 Closed Cab PU]

Originally Posted by alexiskai

An update! I replaced the upper and lower distributor plates with the Bert's (modern) plates. I have to say, the build quality on these plates is excellent. Very sturdy, good materials. Highly recommended.

The good news: It starts! And runs. Very smooth. Also I can turn the GAV down to 1/8 open.
The bad news: It stalls if the throttle lever goes above 3 o'clock or if I accelerate beyond a moderate tempo.

I think all signs point to the carburetor at this point. Thoughts? I have the new one from Bert's but haven't installed it yet.

This is very curious, yesterday installed my new Berts carb, same issue, stalls at med to quick stops.


The previous carb was a rebuild carb put on when my motor which was rebuilt by a model A shop this spring. This carb seems to run slightly rich, and had to adjust the idle mixture to 1 3/4 turn so the motor would not exhaust backfire when turned off.


This is on a rebuilt motor with less than 500 miles. Emailed Berts. Here is their response.


" You have a vacuem leak. Check your intake to block gasket, check intake manifold for a crack, and carb to intake gasket and vacuem wiper lines if you have a vacuem wiper.
We panic stop each carb several times when testing, to be sure that is not to happen.


I say put the new one on and update us.

[alexiskai]

I put the new one on, just haven't had time to drive it around. Will update when I do.

My manifold gasket is new and the port on the intake for vacuum wipers is securely plugged, so if I were to have a vacuum leak it'd have to be from a cracked intake. But I had it off recently and didn't see any cracks then.

[steve s]

Are you SURE you didn't crack one of your manifold's ears when you put it on?

[30 Closed Cab PU]

I understand, I believe you still have the old one installed, or maybe I misunderstood and you have the new Berts on?


If Berts is installed, or if you have yet to install Berts, install it. Then, do not change the screw settings and see if you still stall. If you still stall, note where the screws are set and then do the adjustments and then see if it stalls. This way you can return the Berts to the original Berts settings if it still stalls when adjusted.


If both old and Berts stall at this point, perhaps there is something exterior to the carbs causing the issue. I believe you are supposed to do the adjustments with the motor at operating temp.


If the old carb stalls and the New Berts does not, then the old carb has a problem.


When I installed mine, I 1st adjusted it warm without testing it as I received it, and do not remember exactly the screws were as I received the Carb.

[jm29henry]

Hey bud it’s so great to be getting all of your feedback on your baby! I am amazed at how much Jackson is able to hit the nail on the head time and time again. He also has some amazing how to videos on YouTube .I cannot wait to see how the new carburetor does .best of luck Joe.

[30 Closed Cab PU]

Please post your results, I am struggling myself, and any info you can provide is most useful. Even if the Berts cures you stalling issue.


If it is your old carb, do not know if it has been mentioned , am being lazy do not want to reread this string right now, you can try cleaning it up yourself, checking to see if the shafts have play/are worn, and perhaps install a set of Renners Corner flow tested Jets.