The Stovebolt Site Forums The Shop Area Engine Shop Need help on a timing issue on my 1941

... and don't forget to block the vacuum advance (if you have one) while setting the timing. I found it easier to make the adjustments by cutting a foot or so out of the metal vacuum line to the distributor and replacing it with a rubber hose.

I don't have Chevy specs, but GMCs that use the same distributor say to:

1. set the "octane selector" to zero
2. get the idle speed below 400 rpm (because the distributor's mechanical advance starts that low)
3. start the engine and set the ball on the needle
4. lock everything down and reconnect the vacuum advance
5. set idle speed back where you want it. Mine is 425 in the winter and 550 in the summer to help the A/C work better


Once everything is back together you can see what happens when you play with the octane selector some. The good thing is you can always move it back to zero without needing to hook up your timing light.

My GMC likes the +5 setting. I've never heard my engine ping, though the truck may be making enough noise that I can't.