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Ignition advance and hesitation


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Hey y'all! Guess I haven't been around cuz this site has a new look to it. For about 3 cruising summers I have always had a hesitation from start. I've learned how to drive the car by a little "pump" of the pedal at take off. I've replaced the entire fuel system, rebuilt the pump/carb and replaced the accelerator pump. Fuel/air mixtures screw set and filter's clean also. I was thinking about it so I looked up that symptom again and advance came up. I remember doing the points and timing years ago but that was about it. I notice at the distributor cap a tab marked advance on the left side and retard on the right. I loosened the cap bolt and gave it a 1/8" turn clockwise. Actually, there isn't much movement left or right so I cranked it as far as it could go clockwise. Well, I went to a big parking lot and tried to stall it out by stop/go, stop/go. Nope. Took it for a cruise and tried to hit every red light. It took off perfectly each time except maybe one little hiccup. Boy what a difference! I feel like I'm driving a different car. Maybe now the wife can take it for a spin!! LOL

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  • 3 weeks later...

Howdy - do you have a timing light where you can check the current ignition timing after you cranked it clockwise ?  Or even if you do a static check with a test light to see where the ignition is occurring related to BTDC.  

It would be interesting to see where its currently timed at as compared to before when the engine was  suffering the hiccup before.  Some of the old engines that have a significant of timing chain wear require more advance due to the lag in the valve timing as the chain stretches and of course then retards the ignition. 

1/8th of a turn is a significant amount to rotate the distributor in relation to static ignition timing and then of course total advance. Even though these engines are low compression, too much advance is not good. By the sounds of it, it may have been running with the spark timing  well retarded before

High HT Plug lead resistance can also cause a hiccup off idle as well as the spark will be extinguished as the load comes on the engine to move off from standstill. 

 

Be interested in what you find as to the current / previous settings.

 

More importantly its good that you have cured the hiccup :)

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Does your distributor have the Octane selector tab fitted as per this picture - ( the tab thats shown sitting up against the block and is held in place by the distributor base  ?) 
 Be interested to see what you refer to as the tab at the distributor cap as Im assuming we are talking about the same part ??

 

 

DSCF4323.JPG

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I do have an old timing light but found if I touched the vehicle while running I got zapped. Not a big fan of that! I remember checking it and the mark on the crank was lining up with the indicator so I assumed it was correct. The timing chain is new but I did question how much of a tighter fit it was compared to the used one. Plugs and wires are new. 

Is this the Octane selector tab I've circled? Yes it's what I meant. 

DSCF4323.JPG.6991d5b438db29337138b870c2da8844.jpg.4dc972b43879a7e8dd52609039116990.jpg

 

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Ok so we are on the same page then regards the octane selector tab .

 

Are you familiar with checking the static ignition timing with the engine stopped and using a test light ? Thats as good a starting point as any for ignition timing checking.   And i found both methods accurate when compared to one another ie static vs dynamic checking.

 

The beauty of using a strobe timing   light is that you can verify not only ignition timing at idle but more importantly the amount of total advance.  In my opinion total advance is more critical for engine performance and economy than initial timing at idle hence i tend to tune engines on the total advance number rather than at idle. Not so much with these old girls with low compression ratios but later model engines running greater than 8.5:1 Compression ratios then are prone to detonation with resultant damage incurred if there is too much advance dialed in.

On the Pontiacs I have, i found to have total advance of 34 deg BTDC required initial timing of approx 7deg BTDC whereas the manual for memory quotes  3 deg ?  obviously there may well be some cam drive / distributor drive slack in there that may account for this as well.   

 

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