I finally got the tools I needed to check this stuff. I hooked up the dwell meter and it was sitting at 35 and used the timing light, adjusted the distributor a bit to get the timing mark to 0. But it is wanting to jump from 0 to the 1st tick mark to the left if you were standing in front of the engine. should the mark be solid on the 0? why does it want to bounce like this?

 

I'm not sure I understand what you mean by "it wants to jump to the first tick to the left." Are you talking about the marks on the balancer?

As you read below, keep in mind, I have HEI...But most procedures are the same.

First, make sure your car is at operating temperature, and your idle is set for lean best. I'm not sure about your carb, but for mine (Edelbrock), I attach a vacuum gauge and adjust the idle mixture screws until I obtain the highest vacuum...your procedure may be slightly different.

If you have a vacuum advance, disconnect it. Then, aim your timing light at the balancer. Rotate the distributor until you see 10-12 degrees advance. Zero advance is not good. You'll run lean. Combustion will actually take place outside of the chambers and in your headers/manifolds. Your exhaust will be louder because of this. Not good.

So go for 10-12 degrees. If you hear pinging, or the engine becomes rough, back it off.

Then, attach your vacuum advance, if you're running one, and check the difference. The difference between the two, obviously, is your vacuum advance. Disconnect the vacuum advance again. Now, rev the engine while the light is pointed at the balancer. You'll see the centrifigal advance come in. If your balancer is marked for it, you should be able to verify just how much you have. For most engines, 34 degrees is optimal. If your balancer is not marked for this, Lars has a great page that explains how to mark your balancer to be able to view what the advance is. If you have an advance light, just dial in the advance, and look for the zero.

Once all this is checked, reattach the vacuum, and you're ready to go.


[Modified by joeveto, 9:51 AM 4/29/2003]

 

:iagree: See Lars paper. http://www.corvettefaq.com/redir.asp?site=26

 

skruball73
I am assuming that you have a point distributer in a 73. If this is true your dwell needs to be between 28-32 degrees, or 30 degrees on average. If you have a MSD type of ignition box, the reason for the bounce could be the double fire of the iginition that is typical of these iginition systems up to 3000 rpm.
Ed

 

Hi
This 1 degree jumping could be a worn distributor gear or worn camshaft chain. If I understand you correctly, you mean 1 segment, should be 1 degree. This is not so bad.
Gunther