Setting timing with a Petronix?

[Paul Rossmann]

I have a Series III with the Petronix ignition. Some recent issues with the car inspired a tune-up and I found the timing to be way off (I could barely see the timing mark) but the car seemed to run fine. It seems that I have heard from a couple of sources that the timing cannot be set "correctly" if one is running the Petronix. Any truth to this? Can anyone shed any light on what would be the correct setting for the timing (if it is different at all)?

Thanks.

[greenmeanie]

I have not got one but I don't see why a Pertronix would be an issue. It's basically a hall effect sensor providing a trigger signal so you should be able to set it in the same fashion as any other system.

Now the thing that cannot be varied is dwell as this is controlled by the electronickery. Of course, if you have the Pertronix you should have ditched the ballast resistor for a high output coil for a nice reliable fat spark which will result in better charge ignition which allows you to play with your timing a little but ultimately to very limited effect on a 2.25. You can also play with your plug gaps but after much playing around I never found any significant gain from that either.

Too much advance will show up as pinking at high load. You might want to pull the dizzy and check the advance isn't stuck and also that it is timed off the correct cylinder. Other than that it is either a don't fix what ain't broke or reset to the book values and tweak from there.

Cheers
Gregor

[Daurie]

Also dont forget to unplug the vacuum advance before you set the timing. The timing jumps up quite a bit when one re-connects it after checking the timing.

[luckyjoe]

With a pertronix, I've found it works best to time by ear. I also run a stock coil (really no need for the performance coil), and gapped the plugs to 0.045. Runs great for a 7:1 2.25p.

Regards,

[I Leak Oil]

I had no problem re-timing my engine after installing the petronix. Just put a timing light on it and set it as you normally would. The timing light doesn't know or care what you have under the distributor cap, it's just telling you when the plug is firing. If you can't set it using a light then something is wrong and you better chase it down before it gets worse.
Jason T.

[Paul Rossmann]

Thanks to all. I think my problem was that I did not disconnect the vacuum hose... the ol' girl is running great, but "off the mark" with the vacuum hose connected. I had always heard (as stated here) that one had to tune by ear, and/or the timing marks would never properly line up.

Thanks

[luckyjoe]

Paul,

Just to clarify, in my case it is not that a timing gun will not do the job, but on my 109, I have to view the timing marks through the port on the bellhousing! To read the timing, my head and the timing gun would have to occupy the same space where my dual tank fuel valve and Kodiak heater reside.

So I time by ear cause I've done it that way for many years, many vehicles and find it a very effective method...

Regards,

[Paul Rossmann]

Tom,
Up until now, I had also set the timing by ear (with the Petronix). But when I finally got a light on it, it was way off. I am going to go back to Timing 101 and set with the light and without the vacuum hose... if she is rough, tune by ear as necessary. Thanks.

[lrdukdog]

I used to do the "ear" timing myself. Then my new next door neighbor who was/is a Brit car guy. Told me that you get the best tune-up at a garage with the electric tune-up stuff. He was right! They set the sensors etc and started her up and kept twiking her until she was smoooth and that lasted for a long time. Gas mileage improved as well.
Just my two pence, but it isn't that pricey to let the pros do that part.
You will probably need and older indepent garage to set the carb. at it's best setting. These new/younger folks are all about electrickery fuel systems.
Jim Wolf
Elvenwood Kennel