Reply to "spark timing"

Barry,

That first pic that you posted is from my '71, #1490. 6° was the "factory" setting, and that is what I have used for the last 128k miles on my never rebuilt original 351C. At the time that I placed the yellow mark on 6°, I did not own a dial-back timing light.

Rocky's posting of the three emissions placards is my pic also. If you look at the bottom right of those three placards, you will see a year to which the vehicle emissions comply.

The first two placards show 1971, but with two different initial timing settings, 6° and 10°. The 6° is from my '71 (build date 5/71), and the 10° is from a late '71 with a build date of 10/71. From what I have observed, the 6° was changed to 10° late in the '71 "production" year.

Also note that the distributor point dwell increased from 29°-24° to 34°, which indicates that the distributor was changed to dual points instead of the (earlier) single points distributor. This was still in the '71 "production" year.

The third (bottom) placard is for 1972, and shows 16°. The 1972 cars had the compression ratio lowered to 8.8:1 with open chamber heads, and the cam specs were changed.

As George pointed out, those initial timing settings were for tailpipe emissions, and not (necessarily) for performance.

John