Optimal Timing SBC 350

[kna4977]

Decal says 8 but that was with 1972 fuel. What is optimal initial timing with todays fuel?

[geezer#99]

I run mine at 14 here at sea level.

[kna4977]

Originally Posted by geezer#99

I run mine at 14 here at sea level.

I’m in the Dallas TX area. Was thinking maybe 10-12 range?

[geezer#99]

Start at 12 and bump it up a couple degrees until it pings or is hard to crank.

[Willshook]

Initial timing is just one aspect of timing - mechanical and vacuum advance are key for performance, fuel economy and drivability.

For mechanical advance you want ~36 degrees at 3K RPM. If the initial timing then ends up over 14 degrees...then you should do some digging to make sure the timing marks are right. Kits are cheap from MSD and Mr. Gasket for weights and springs.

Vacuum advance is a little more tweaky, but unless you have (or want to install) an adjustable can you can ignore it for a daily driver. Just make sure you're using manifold and not "ported" (above the carb butterflies) vacuum.

If you don't want to monkey with this, 10-12 degrees initial is usually in the ballpark. I wouldn't run anything more than that on a daily driver. There's no advantage to "more" timing...

Lots of great articles on this around, but the basic numbers are very well proven on the road, track, and dyno...

[Dead Parrot]

A lot of the early 70's timing numbers were intentionally less then optimal for emissions reasons. If the vehicle had the AIR system, they wanted some unburned fuel in the exhaust so it would burn off when the fresh air was injected in the manifold. Better for clean exhaust, not so much for power and fuel economy. Also, the more advanced the timing, the more NOx that gets made.

If you don't have to worry about emission checks or your location doesn't check timing, then for a stock or mostly stock 350, around 12~14 usually works. Don't worry about exact numbers. Keep in mind you are reading off a mass produced timing mark on a press fit damper using a stamped timing mark tab spot welded to a stamped timing cover. There is a bit of slop in the system.

Do what Geezer said and sneak up on it over a couple of weeks. Unless you want to seasonally adjust things, best to do during a 100*F hot streak. If it starts easy when hot on a 100* day, you should be good for any weather.

For OP, I would adjust to 10 and see how it reacts. Then go from there. It will probably cause a higher idle so you may have to readjust that. While you are adjusting, make sure your vacuum pot is still working. They often quit and not get noticed as the main effect is lower part throttle cruise economy. If your vacuum pot is currently on ported(often the factory option), switching to manifold will also cause a increase in idle speed so another adjustment needed.