I live in high altitude CO and I have a 200ci 1970 Mav. It says on the valce cover sticker that it should be 6 deg. BTDC and its at about 10 deg BTDC. I got the car a little while agoa nd just got around to timing it. 10 seems a little high to me but I am in high altitude so should I put it at 8 deg BTDC? thanks -Drew
I always set the timing to the highest idle speed it would run clean at and steady on a vacuum gauge then run the light on it make sure it wasn't going to have 50 degrees of total and ran it consistently it would be 14-16 degrees your might be higher or lower depending on the altitude
The only way to time your engine for maximum performance is to keep advancing the timing by 2 degrees at a time until you get spark knock. Once that happens set it back four degrees and lock it down. That means you have to advance it, drive it for a few days and if you don't get spark knock advance it again.... You have to drive it like you are going to be driving it and you have to drive it hard too. If you get any spark knock then you back it down 4 degrees. OK, There is one other way to set your timing - on an engine dyno.... but that's for rich kids (or lucky ones)
Sorry, but that is not the best way to do it, or even a good way. Pre-ignition (detonation) can occur even when you're not hearing it, so timing by ear is not going to be accurate. You can do so just to get it into the "ball park", but you should then use a timing light. 6 degrees is the factory setting. It is normal to advance timing 2 to 4 degrees in higher altitudes such as where I live. I actually ran my old motor at 12 degrees initial, but that was at 6000 feet above sea level and with an 8:1 compression ratio. I don't know for sure where I'll be running it on the new engine (9.5:1). I figure anywhere from 8 to 12 degrees initial though. 38 degrees total is the maximum for 302s...
I find that the 250 in my brother's '72 and the 200 in my '69.5 run the best at the factory specification of 6 degrees BTDC. I can advance both of them a ton before they audibly detonate, but they get sluggish and alot worse fuel mileage.
