Am I correct that the ignition timing on a 383 Plymouth 1970 engine is 12.5 before TDC. Just want to check mine today and don't have literature handy.

Thanks.

That's not correct. It might be 2.5 degrees,but the decal on my 70 RR 383 engine says set it at TDC

Wow! thanks so much for the info.

Leave it at 12 if it runs good there.

Get a baseline & see what you have now:(A) at idle(vac disconnected)(B) total(vac disconnected)(C) and at what rpm it stops advancing & (D) what springs(turn the crank until you hit the 2 places where you can see them)& see if they're the orig light one and the thick one w the long loop on one end. The TDC @ idle setting was for the very strict emission std's of those days & the bandaid way they attempted to control them. You most likely can advance it, If no ping & no kickback when starting there's no problem & to max it out you'd probably want to shorten the slots/change springs and do alot of experimenting until you get the exact right combo for your eng(you'll get to where you can get that clip out of there on the 1st try ).

i think my 68 RR 383 4-speed sticker says 0 also my 383 is basicly stock with a cam a size bigger than stock. i have mine set at 12 btc runs much better that way.

Check your total timing with the vacuum advance disconnected. If you are at 34-36 degrees leave it.