> I think stock timing is 4 degrees ATDC, at least
> it was on my 74.
The 4 ATDC spec is only with the vacuum retard connected and working (in spite
of what some manuals say). Although US law at the time required that the timing
be set in that condition, IMO it's better to disconnect and plug the vacuum
line; then set the timing to the "static" value in the book (10-12 BTDC as I
recall). Then it's up to you whether to reconnect the retard or not.
> However, that year the car
> had a mechanism that would advance the timing a little bit whenever
> the engine temperature rose to a certain level. In my case, whenever
> the engine got hot, the timing would advance, and then car would run
> fine without stumbling.
That mechanism was the TVS; which disconnected the vacuum retard as above.
If you bump the timing up with the retard connected, then you risk
over-advancing the ignition under load (when the retard is no longer active).
Usually this will manifest as spark knock ... but I have a broken piston in my
collection that was caused by knock I didn't hear.
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