My ignition timing is going crazy, very unstable

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1966DartConvertible

1966DartConvertible

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I trued setting the ignition timing today to 2.5 deg BTDC as per factory but the mark was running all over I.e. Very unstable. I set the thing the best I can and took a long drive, after about 50 miles of driving the engine start pinking badly at anything above 1/3 throttle. I suspect the timing went crazy and advanced by itself.

What could cause this? The spring inside the distributor? Is it hard to take the distributor out?

Thanks

Syed
 
Broken rotor button ? Is the keeper holding the distributer so it doesn't move by hand?
Factory tune up specs were meant for real gasoline. Today you will need at least 6 to 10 before TDC.
 
RedFish said:
Broken rotor button ? Is the keeper holding the distributer so it doesn't move by hand?
Factory tune up specs were meant for real gasoline. Today you will need at least 6 to 10 before TDC.
Click to expand...

Yes the distributor is tight and won't move by hand. What puzzles me is that I can set it at 2.5 n it runs perfect for about 20 miles then its like it has mind of its own. Even if I set it at 6-10 static timing by the time I drive a good distance, it will be off again and start pinking.

Do u think I need to take the distributor out, FYI the timing chain n harmonic damper are new.

Syed
 
how about disconnting the vacuum line and running without it, eliminate that part of
the distributor.
 
ok what octane fuel o you run? here in the states you can get to 10* on most motor's on 87...

for checking the timing you need to disconect the vacuum line from the carb to the distributor, but remember to plug it with a golf tee or something so you dont have a leak...

then set the timing around 8*, reset the idle, and re check timing...

now tighten down the bolt for the distributor, after it is snug try to turn the distributor... if it turns there is another bolt under the dizzy for more adjustment need to tighten it up...
 
Could you have stretch in your timing chain? That could cause timing variation.
 
How are the plug wires. ?Could a bad old wire be tricking your timing light. Try your light on another wire to see if its erratic. Check the timing cold and hot.Maybe its not timing at all and its leaning out when the choke pulls off.
 
What led up to this? Why did you change it in the first place?

Slants have a bolt UNDER the distributor case that tightens the bracket against the distributor, and the bolt you SEE that tightens the bracket on the engine block.

I'd be suspecting something in the dist is wrong, or the plastic drive gear is AFU

You have a shop manual? Download a 66 manual for free here:

http://www.mymopar.com/downloads/servicemanuals/1966_Plymouth_Service_Manual.zip

2p28g.jpg


3588dj5.jpg



A photo of the bottom showing the clamp bolt

2efunac.jpg
 
Could,be timing jumped a tooth or and I have had this scenario happen a few times with a bad coil after the engine gets hot.
Try a new coil or check your output.
Also male sure you have good plug wires with no hot spots, And if they are questionable try a new set.
 
You may have a broken or weak spring that retracts the weights of governor controlling mechanical advance. Also sticking governor weights will cause fluttering timing at idle.

After 30 years or so, some of the parts on our cars become crusted from dried lubricant, and corroded from just being around. The distributor’s governor is exposed to the elements and often regular maintenance as well.

Disassemble top side of distributor to examine governor springs, clean and lubricate the action of its weights. Slant six distributors require a few drops of light oil be placed on the felt located in distributor shaft under rotor button at every tune up 12 months, or 12,000 miles. This oil point lubricates the innards of the distributor.

To remove top plate of distributor, look under oiling felt for a horse shoe shaped wire retainer that acts as a spring clip holding governor on the shaft. Sometimes it comes out easily, and sometimes it is a royal PIA to extract, but once it is removed the plate covering the weights comes out easily.

Pay attention to direction of slotted weight retainer as the rotor button attaches to this part, mark it if needed, if this part is reassembled 180 degrees from its original position, the timing will be out 180 degrees when distributor is reinstalled in its original position, and engine won’t run.
 
That is a common indication of a worn timing chain, but could be something simpler mentioned above. Don't assume it is the timing chain without doing the diagnostic for that first ("lost motion" in distributor rotor when turning crank forward then backwards).
 
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