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Old 03-14-2013, 03:44 AM
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Originally Posted by PontiLac View Post
in the 9:1 +. a ball park number is good for me thank you

so im guessing pining is not a detonating issue, 91 octane should be just fine right? its a timing or air to fuel mixture problem?
Could be timing, f/a ratio, or even a hot spot in the chamber(s). Again- be sure there's no vacuum leaks.

Look at the plugs to see if they're the right heat range and at the plug color to see if they look lean.

Get the carb secondaries working. Using the vacuum reading at idle, see if the power valve is correct. Again- if the carb had been used previously then allowed to sit dry, the PV needs replacing.

Map the timing curve and see what the initial and total is, and at what rpm the total is all in by. See how much the vacuum advance is adding. Note whether the vacuum advance is connected to manifold or ported vacuum.

See that the mechanical advance and vacuum advance mechanisms are working freely and not hanging up.

If you don't have a dial back timing light you can make a temporary timing tape (or buy one), in order to use a regular timing light to see where the advance is at various rpm. Post #8 has a link to info on timing.

After you are sure the total timing is not excessive, take it out and see if it's still pinging. If it is, it's time to look closer at the fuel/air delivery. Or the possibility the heads were milled excessively, or that you may have domed pistons.
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