TDC Misalignment Question

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  • #581335

      Hi all. I’ve been working to verify TDC on the #1 plug, and the result I’m getting is a retarded 18 degree delta between my TDC mark and the balancers TDC mark. I verified using piston stop marks on the balancer for both clockwise and counterclockwise rotation of the motor, then dividing by 2. The dizzy does indeed point at the #1 cylinder when the balancers mark is at zero on the timing tab, but at #3 when I set my new TDC mark at zero.

      That said, the motor runs and starts OK, for the most part. Hard starts at times, but idling seems to be consistent with no dieseling. The dizzy is rotated far counterclockwise, to the point where i have to jimmy the air cleaner to seat properly, I ‘think’ that I’m hearing some very high pitched pinging at idle, and I do have a strong rich smell from the exhaust. I’m set at an initial 14 degrees advance against the stock timing tab, or 32 degrees with where I’ve measured TDC to be. I’m not sure about mechanical as I don’t have a tach to verify.

      After speaking with a friend, the question is could the dizzy be ‘off one tooth’, where its pointing at #3 for the first in the firing order, but compensating the misalignment through a lot of advance? I am looking to rotate the dizzy one position counterclockwise to line up with my TDC mark, and see where it stands.

      Sorry for the long post, but wanted to be sure I was illustrating this properly. Any insight would be appreciated.


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    • #581364
      college mancollege man

        What year,make,model and engine size are we working on?


          Sorry, thought I had created a signature with that info. It’s a ’67 Camaro with 350 SB. Thanks.

          EricTheCarGuy 1EricTheCarGuy

            It doesn’t sound like your distributor is positioned correctly. For me, I just line up the rotor with the #1 port on the distributor cap. It can be tricky, but I don’ do any fancy calculations or anything. It’s either in time or it’s not. Yes, you also have to get the housing in the correct orientation but I normally mark it before removal so I get it back into the same spot. Once you’ve got it positioned correctly and it starts, you’re going to have to set the ignition timing with a timing light. Here’s a video on how to find TDC easier.

            Keep us posted.


              Thanks again Eric. I actually watched your video a couple of weeks ago. Very easy to understand which is much appreciated!! I haven’t been able to get to this just yet. I’m planning on it tomorrow.

              With the car running OK, I just find it curious that the timing has been off as much as it appears to be (18 degrees) with the car still running acceptably. I say acceptable, but it is a bit unpredictable at times, mostly on startup and slightly choppy idle at times, but nothing that someone else would really notice. Which again, is it possible to advance the dizzy so much that it can compensate for the rotor to be pointing one cylinder off?

              I also have a new Pertronics dizzy that I’m putting in with new coil. Should be a big improvement over the original AC Delco points system, and hopefully more reliable on startup and better distribution up the power band.

              I’ll let you know how it goes. Hopefully no CAR-BBQ! 🙂

              Lorrin BarthLorrin Barth

                The timing mark on the damper can occasionally move. The inner part of the pulley is connected to the rim with rubber.


                  Thanks Barney. I had thought about that, as the car has been raced in the past, which might accelerate an issue like that. I’ll reaffirm the new TDC tomorrow and adjust the new dizzy accordingly. Thanks again!

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