How many degrees BTDC?

[steve1973]

How many degrees BTDC should I run?

1973 CJ5 , AMC 258 i6 / 4.2l 6 cylinder, 3.73 gears, 30" tires. The emmision sticker and Jeep Tech service manual both say 3 degrees BTDC. For mods, I have a weber 34/34 carb (which is fantastic) Pertronix ignitor II with 50,000 volt coil, MSD 8.5 MM wires, NGK plugs and .040 gap and I live at sea level. No other mods. The Jeep seems to run best @ 8 degrees BTDC. Where should it be?

 

[Old Dog]

If it likes 8* I'd leave it there, it won't hurt it. Just listen to be sure you don't get any ping under a load. If you do back it off a couple degrees.

 

[kencc56]

You can check out the link below. It tells you how to vacuum tune for timing.
Classic Inlines You also can adjust the carb this way. I have a Weber upgrade & it's a good way to check your carb settings against Weber's "lean best" adjustments. You can buy a decent vacuum gauge for $20-$25 at Napa.

 

[steve1973]

Thanks,
I forgot how usefull a Vacuum gauge can be on a carb/distributer engine.