Ignition problem

A

aermotor

Well-known member
In my original post (fuel or ignition problem?) posted 8/11 I miss spoke saying the problem was fixed. The carb was taken apart 2 times and could find no problems, I have checked the timing several times with a New Rex tool. I still have missing. The car starts easy and from there on things go South. Idle is pretty smooth, as I start to press the gas pedal the miss becomes more prominent and the more I press the engine begins to "lug" down. Starting with a constant speed slightly above idle pulling down on the spark advance lever same thing happens. I did notice something curious to me, #1 and #2 cylinder will spark from the wire to the spark plug strong 1/2" away and the #3 weak from 3/8" inch away and # 4 weak from 1/4". What is going on with that and does it have anything to do with above problems? I removed all 4 spark plugs, cleaned and reinstalled and ran for about 1 min. They all had about the some amount of soot. I did not do a compression test as I don't have a leak down tester. I don't feel that compression would have anything to do with the problem, considering the above observation to be the problem.

John
 
A leak tester isn't a compression gauge. A compression gauge should be all thats needed.

Refresh my memory, are you using the modern upper plate ?

The engine should run fine for all speeds above idle with the spark lever at 9:00-9:30.

But, it sounds to me as though there is a carburetor high speed circuit issue. Did you spray cleaner and compressed air thru all passages to make sure they are clean ?

Check the gap of distributor rotor especially at #3 and #4 And look for a crack or carbon track.
 
Check the distributor cam and shaft bushings. If these are bad, the points may not be opening the same amount for each cylinder. To check this, turn the engine over by hand and check each cylinder to see if the points are opening the same amount. At the same time, check the rotor to distributor body gap for each cylinder to see if they are all about the same. This can cause a strong spark for some cylinders and a weaker spark for others. The spark should be about the same for each cylinder.

Check the upper plate for looseness. With the points open, grab the arm that sticks out of the distributor and try to move it side to side. If the point gap changes by very much, this can cause uneven spark.

My opinion,

Chris W.
 
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The above 2 suggestions are very valid and I will check and also trade distributers with my speedster, which runs very good. I can't swap carbs as the speedster has a 2 barrel downdraft. I did clean the carb and blew out all the jets and replaced a couple for good measure. I am using the modern upper plate.

Thanks, John
 
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When cleaning the jets, did you blow out the passageways as well ?

The wireless upper plates can be a problem, they'll lose the ground. Adding the wire solves it.
 
Patrick L. said:
When cleaning the jets, did you blow out the passageways as well ?

The wireless upper plates can be a problem, they'll lose the ground. Adding the wire solves it.
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Yes and I also soaked it in carb cleaner for 24 hours, when I change the distributor with my good one I will know for sure. Should have done that in the first place but I do want to have booth cars running.

John
 
aermotor said:
Yes and I also soaked it in carb cleaner for 24 hours, when I change the distributor with my good one I will know for sure. Should have done that in the first place but I do want to have booth cars running.

John
Click to expand...

You can only drive one at a time. Most people have a "modern" car that can be used as a back up.
 
Katy, that’s probably true, but my personal philosophy, and for my own peace of mind, once restored or refurbished, I have always kept all my A’s running and able to drive at any moment. I have never considered one as a parts car for another. Today I only have two. They are carefully maintained and serviced and always ready to go. If something fails, it is immediately addressed. This is just the way I feel most comfortable with my cars and the hobby.
 
if you have good spark at 1-2 but less at 3-4 perhaps there is a bad spot in the cap and the spark is being diverted internally---try another cap also check point gap to see if big difference between 1-2 and 3-4
 
aermotor said:
Where would the added wire go?

John
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As in the original distributor the wire goes between lower and upper plate to the points stud.

The modern wireless eliminates that wire using the brass ring and the points stud tab to contact the brass ring. Use an original lower or remove the ring, remove the points stud tab and affix the fine flexible wire. Basically you end up as original with modern V8 points/ condenser.
To make the modern points easily adjustable I mark the upper plate and then drill/file a screwdriver slot to match that of the points.
 
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