Timing and plugs

[David McIntyre]

I have a 67 firebird with a 413 engine, 6X heads, what's the best plugs and at what gap. and what's the best and most timing with 93 octane

 

[melsg5]

Timing should be set with a curve kit installed, lighter springs and stop bushing. Total timing with vacuum advance disconnected 36 degrees. If a stock ignition the plug gap is .035 if modified .045. and the plug would be a R45TSX AC.

 

[David McIntyre]

I have a HEI distributer, I read on one site that they were gapping the plugs at 80, and some were running as much as 44 on timing

 

[melsg5]

the .080 gaps were necessary for the lean mixtures caused by pollution standards. I'm going to asssume your not trying to get your 67 to pass later emission requirements. The 36 degrees is mechanical advance only. You get additional advance from the vacuum advance unit which may raise the total to as high as 52.

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[David McIntyre]

OK, I didn't know why they were gaping the plugs so wide, this helps alot, I have a pro comp distributer, so I should change the springs to let it speed timing quicker I'm supposing

 

[melsg5]

Your total timing should be reached at 3,000 RPM with 36 degrees total with vacuum, if it has one, disconnected.