The Stovebolt Site Forums The Shop Area Engine Shop Octane selector or grease cup

I have read several posts about the octain selector on the distributor but can't remember if the engine was 216, 235 or 261, or all three. there is a dial like device on my 216, but it is filled with grease. If this is the octain selector, how does it work? Should the grease be there? Should there be such a device on my 59-62 231? Can anyone help narrow this engine down to a certain year? #3789925, no number on the milled area beside the distr, this number is beside the clock like dial (B 5 8). thanks, Ron B.

correction to previous post, should read 261 in stead of 231.

The "925" is a full oil flow 261. The B58 means it was cast on Feb. 5, 1958.

Jim Carter has a good technical article on the 261.

Carter.

Check this picture: http://1929to1954chevy.web1000.com/02/154.htm

The arm (2.418) has a scale on it. The octane selector was used to make small adjustments to the timing to account for variations (varying quality) of the available pump gasoline.

Jim

That is a grease cup. Am not sure why some call it an octane selector. But what was used as an "octane selector" is actually beside it, the spark advance or retard device, at the base of the distributor.

There is a 1/2" bolt holding the plate that holds the vacuum advance to the block. There is a slot in the plate, and if you clean off the grime there should be markings on there. It lets you bump the timing up or down a little without loosening the distributor. This is true on all stovebolt engines.

Ron:

That "dial like" device SHOULD be filled with grease. It's not the octane selector - it's the distributor shaft grease cup. It's a regular maintenance item. You are supposed to turn that cup Clockwise about one full turn every few thousand miles (check your Shop Manual or owner's manual).

Yeah, the octane selector is the series of slashes on the bracket holding your vacuum advance to the distributor.

I STILL haven't figured this item out. You are told to set it to "zero" by just about every darned tune-up manual I've found. You tweak the distributor and carburetor to fine tune, BUT NO ONE writes about what the heck or how you mess around with the octane selector ONCE you've timed the engine.

Me, I'm running all my vehicles on this low octane/no-lead stuff and haven't been able to teach myself how the octane selector should be adjusted to account for today's gasses.

Whining over now...

According to the manuel after you're supposed to adjust the octane selector 'till you get a slight ping under a load.