The Stovebolt Site Forums The Shop Area Engine Shop Distributor question

I'm in the process of getting my '50 running & have a concern about my distributor. Is it normal for it to turn a short amount? This doesn't seem right to me, but then again, I'm not real familiar with the advance setup that was in use when this was new. Also, what is this "octane selector" in figure #32? Is this something that I need to adjust to make the truck run? I should clarify the distributor movement question. It is taking place at the linkage you see in the picture with the "octane selector".

Thanks in advance!

The distributor is held in place with a bolt on the plate. It should rotate in the hole in the block if the vacuum advance is operating correctly. Watch the distributor as you rev up the engine, it should move. You can check the timing with a timing light through the hole in the bellhousing above the starter. The pointer should line up with the ball in the flywheel.
Fred

Thanks much, Fred.

I didn't know 50s still had the octane selector. Just set in on "0" when you set your timing. It allows you to advance or retard the timing up to 10°. It was required when the quality of gas varied a lot.

I think the octane selector was on 235/261 engines in all years.

Most people in the shop at the time used the octane selector to set the timing, because that bolt is easier to get at than is the 'proper' screw behind the distributor, and the octane selector wasn't used for its original purpose- which Tiny explained. In the picture in your manual, the square nut behind the distributor is the other end of the 'proper' screw, which is often difficult to get at. If the timing is off very much, you have to loosen the clamp and turn the distributor to get the timing where you need it- ball at the pointer, with the octane selector at zero, as originally intended.

Also, if you are wondering about the big cup behind the vacuum advance chamber, its a grease cup. Clean it and fill it with fresh chassis grease and turn it in a little every couple of thousand miles or so. The original specification was every 1000 miles. When the cavity inside the housing is properly filled, the cup resists turning- if it turns freely, like a loose nut, keep turning until it resists. The grease keeps the bushings lubricated.

Harvester

Thanks guys...that's good stuff to find out.

Sometime in its past, it had a '54 235 swapped in. The distributor doesn't have the knob on the octane selector...looks like the picture all except for the knob on the end. Could even have a different year of distributor, for that matter.

The octane selector doesn't have a knob; a bolt holds that bracket to the block. To use the octane selector, you would loosen the bolt and move the whole bracket to change the spark timing to eliminate detonation (or cause it, if you go in the wrong direction) that results from using fuel that has a lower octane rating than what the ignition timing was originally set for.

Where is the knob located? It sounds like it is holding the octane selector bracket to the block, in place of a bolt. Is that the case? Someone in the past may have replaced the original bolt with that knob in order to make it easier to adjust the timing with the ocatane selector- but the original bolt was pretty easy to loosen.

Harvester

I guess I was thinking that the knurled part on the selector was a knob that you turn to adjust, rather than rotating the assembly on the distributor shaft. That makes more sense, now. Thanks for having patience with me on this.

a.d.

I know what you are referring to and it was pretty cool looking. My bet is that the knurled-knob-adjusted octane selector was last used in 1936. I have a picture of one on a first-generation 194 cu stovebolt engine - I'll post it, if I can find it.

Tim

Wait...hold the phone, backup the bus....is that little canister with the knurled edge around the end the grease cup? Harvester, please pardon me for being so dense. It just clicked with me on what I'm seeing in that picture. The light has just come on...

...sometimes it just takes me a little bit...

Yes, I think you are looking at the grease cup, and I see how you might have thought it had to do with the octane selector; I hadn't made that connection. The cup screws onto a fitting that is screwed into the side of the distributor housing, below the 'bowl,' so to speak. In the picture in your shop manual, it looks like the cup is located behind the vacuum advance chamber- it is, but it is lower in the housing. Unscrew the cup- it should have remnants of grease inside. Clean it up, fill it with fresh grease and screw it back on- although it might be a good idea to clean the other part of the fitting as well. A piece of wire should work well enough for that.

Harvester

Here is a 1934 octane selector with knurled-adjustment-knob. You can also see the grease cup.

Thanks for the pic, Tim. That online manual is the neatest thing since pockets on a shirt.

Here's what I found when rebuilding my distributor, guess you can turn the grease cup too many times! Ed

That little disc goes ahead of the spring and stops the grease from spilling out onto the shaft. When you force the grease in with a turn of the cup, it oozes around the disc.

I didn't read all of the posts above but in the shop manual it also shows an octane selector for the '54 and my truck has it to verify this.