Before ECMs and EFI where you create 3D maps to vary the setting depending on specific load, RPM and other inputs, timing was set mechanically and as such, quite compromised and limited. Add to that the fact that most mass produced engines are knock limited, meaning as you increase timing you will eventually create knock or a “knock event” before you get to the most efficient timing possible.
Then there’s the fact that optimal timing is not constant. It depends on parameters such as AFR, RPM, load, fuel grade, temperature, barometric pressure, etc.
In the end, it’s a false sense of accuracy to endeavor to set timing at 60 year old factory specifications on a vehicle with mileage, age, and untold modifications by now. Perhaps a good initial target if your marks are intact and accurate, but by no means an absolute or a necessity.
Jim
Highly doubt that its the chain. If it was the chain the engine would barely run or have any power. Put the timing light in your tool box. Old engines have a bad habit of slipping the outer collar of the harmonic balancer. So if you're
the type of person who only sets timing with a light it's going to be difficult. I would encourage you to abandon the light for right now. At idle bring the timing up till the engine speed flattened out. Then dial it back till the engine bogs. Just the
slightest little bit. Lock it down. Take it for a drive. This is the old school method of power timing. Every engine I have ever worked with has had a slightly different tolerance for ideal timing. I rebuilt my 440 3x for various reasons. Each time
with a different cam. And each time desiring a different advance on the distributor. If the timing is too quick on initial. It will crank hard when hot. Just pull a little more timing out till it cranks satisfactory. This is the way I set all my mopars
and all I work on For others. Once you find the sweet spot. Check it with the light. You may have to make a new mark on the harmonic balancer it will be soo far off. Now if you install a new harmonica then a timing light is a great tool.
My opinions have been shared here and may not be shared by all who read this. That is ok. This is the way I do it here in Indiana.
Jason
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