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 Posted: 07-15-2015 05:15 pm
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blawrence
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I have a 1973 to which I have just fitted new toothed belt and all me sprockets. I have also fitted a Petronix flame thrower distributor and a MSD coil. Now the static timing for smooth idling seems to be 30 degrees BTDC. Revs drop significantly at 10 - 12 degrees BTDC. Is this what I should expect with this set up?

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 Posted: 07-16-2015 06:03 pm
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Jensen Healey
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You'll want your total advance to be 32^. How much advance does the Pertronix distributor have? Just subtract for the proper static setting. You could cause engine damage at higher rpm with a high static setting.

Idle quality issues indicate another problem. I'm thinking incorrect timing marks, vacuum leaks, phasing issues and the like.

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 Posted: 07-16-2015 08:58 pm
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blawrence
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Many thanks for this information. I don't know much about the distributor, it was among the spares that came with the car and I have only just decided to try it out. The part number is D1706, which must be an old number since I cannot find it on the Pertronix site. I did get the car started OK With simple static timing method, and once warmed up I observed the timing mark with my strobe light. It seemed to run best with the light showing about 30^ BTDC. I was not expecting this, but from what you say, maybe I should actually set it at 32^ as seen on the strobe. Am I understanding you correctly? What rpm do you recommend when setting dynamic timing to 32^ BTDC?

Last edited on 07-16-2015 10:44 pm by blawrence

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 Posted: 07-17-2015 07:12 am
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Tim Murphy
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I remember going thru something similar years ago. At the regular setting (8*BTDC?, don't have my manual handy) the idle was a bit lumpy with an occasional misfire. At around 30*BTDC, it increased in RPM's and smoothed out. Its just a trick the Engine Gods play on us mere mortals. The car is not drivable at that 32* setting, no power and possible engine damage.

Set your idle timing at the factory recommended setting. Since you are using a timing light, you can check the advance at higher RPMs. Max advance (about 17 additional degrees) is achieved at around 2,500 or more rpms. I think you will have to accept whatever the distributor gives you for the present.

The JH will never idle like a modern car, it is usually a bit rough in comparison. You will need to eventually balance the carbs. For the Zenith's there are a couple special tools (a airflow measurer,and special,long hex key for the carb needle value)to do properly. For now you can adjust the throttle to give you more rpms. A cold engine will idle about 100-200 rpms lower than a hot engine IME.

Congratulations on changing the timing belt and sprockets. That was always a "scary" job for me. Take care and good luck.

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 Posted: 07-17-2015 11:41 am
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blawrence
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Many thanks, Tim. Did you have the Pertronix distributor in your car at the time, or some other type of electronic ignition? I appreciate your congratulations on my recent belt and sprocket change. It was scary but not as bad as the thought of my belt jumping over my badly worn sprockets.

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 Posted: 07-18-2015 03:45 pm
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Jensen Healey
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As Tim says, set your static timing to factory specs. You can play around a little and go to 12^ but no more.
The Pertronix distributor is functionally the same as the stock unit.

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 Posted: 07-18-2015 04:01 pm
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blawrence
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Thanks again for this information. Yesterday I was driving around quite comfortably at 30^ BTDC as read with my strobe, but clearly this could be a problem. I will go back to a strobe light reading of 10 to 12^ and try some other adjustments to get smooth idle. Any other information to help me with this would be appreciated. I guess spark plug gaps need to be increased, and maybe I need to change my plug leads.

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 Posted: 07-18-2015 11:15 pm
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Tim Murphy
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This, if the link works, may help. Also, the JH factory workshop manual, as terribly written as it is, is still a necessity for every JH owner. I have an older Allison electronic ignition system using the stock distributor. Take care.

https://sites.google.com/site/johnsjensenhealeywebpage/maintenance-projects/2-pertronix-ignition

Last edited on 07-19-2015 12:18 am by Tim Murphy

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 Posted: 07-19-2015 01:29 pm
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blawrence
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Thanks again, Tim. The link works and the article is very helpful.

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