The Stovebolt Site Forums The Shop Area The Electrical Bay 1953, 216 distributer issues

Evening all, just recently I had a miss, Found the distributor to be wobbling a tad. No big deal. Had a spare, Pulled it apart cleaned and replaced the shaft bushing per other post's, greased it and started to put the new cap and rotor on. When I tore my old one down, I noticed that the rotor burn marks were right at the bottom of the contacts on the cap???? Reading more, I checked the shaft length and its just under 1 inch. So it should be a short cap and rotor?? Just for the hell of it, since it is what I had before, I cut away the old cap to see where the rotor was lining up with the cap contacts. It appears to be exactly the same area as my original. Just under the cap contacts. I'm guessing a easy solution would be to use the long rotor instead of the short. This should raise my height for better contact surface. Has anyone ever seen this before? Any input would be welcome,
thanks, jim

I must have missed that one. What shaft bushing Jim? In the second generation Chevy six
distributors that I've seen the shaft runs right in the cast iron housing bore.

The electrons are going to seek a sharp edge or point, that's why the cap appears burnt at
the edges of the contacts. Ever notice those Franklin rods atop buildings out on the farm?
Theory is that a pointed lightning rod actually ionizes the air around itself, causing the air to
become conductive. Having the correct gap between the cap and rotor is calculated and
using the correct cap and rotor for the model distributor you have is important.

dg

Morning Denny, You were up a little late!
What I called the shaft bushing is more commonly referred to as a "plug". Tim and Pre '68 Dave went through this around 11/14, in a post on distributer play. Sorry for the confusion!! I do understand current flow, but as I tried to relay into words, that have to come across my brain first, is that the rotor is running below the contact points of the cap. If the rotor was 1/4 higher it would be running flush with the cap contacts and therefor a better connection or arc would occur, and then there would be no arch jumping or burnt spots. I have researched this situation to make sure the cap and rotor are correct for this style distributer. In a previous post, Paul_WNC asked about the different caps and rotors to which Pre '68 Dave responded with the different pictures of the shaft lengths, and what cap and rotor went to those distributers. I do have the short shaft and per the post should be using the short cap and rotor. This was typical on both of my distributers?

Right, thought you had found a distributor with a "shaft bushing".
Many V8 distributors did have a replaceable bushing that the
shaft ran in.

Sorry if I misspoke on the cap and rotor. Haven't ever had the
sort of alignment problem you're encountering nor have I ever
had the need to question it.
However, the cap and rotor don't make contact so the arc has
to jump across the gap and burning over time is the
inevitable result.

dg

If the cap contacts are 1/4" above the rotor, you have a serious problem. The rotor should spin within a few thousandths of the cap terminals, and the gap that is jumped should be very short. If you're jumping a 1/4" gap inside the cap, that's several times the plug gap. I'm surprised the engine runs at all with that much voltage loss before the spark gets to the cylinder. It's probably got a horrendous miss under load, right?
Jerry

Jer & Denny, the cap contacts are just above the rotor. 1/16 of an inch or less. Yes, the truck did run,and it ran real nice. Sweet had it up to 77mph a month or so back! I ordered a taller rotor and I'll see how that looks. I'll take pictures of the original rotor in line with the cap and the new rotor and post them. Just doesn't make any sense to me of why this is???

If it's that close, a taller rotor will hit the cap. There's a big difference in the rotor height, and the tall cap and rotor were used with 12 volt ignition systems that could arc over to the breaker plate when a plug wire open-circuited or fell off.
Jerry

Ok, Pretty sure I found my little problem. Looking back through some old post, Tim attached a parts breakdown for the 216 distributer,( old car manual project) "Thanks Tim". It showed that only in "53" did they use a different rotor. It's 15/16 tall. The others are 3/4 for the short cap and 1-3/16 for the tall if I'm correct. Please correct me if I'm not! (It's ok, I'm married, I'm used to being corrected) This would give me the extra height that I need for a good contact. The part number that was on that page was a 820445. Now I have to find it!! Does anyone know the modern part number for this rotor???

Good eyes?, Jim

If you find that cap/rotor, please post brand and part numbers.

I can't take all of the credit. I was PM'd by a fellow 53er who pointed out that for some reason, Chevy did some weird changes with the 53's only! Thanks to him!

Someone is misreading the parts book
In regards to rotors, even though the listing in the parts book can be a little confusing for 1953 it reads:
1933-52 All (except standard),1953 all with 216. #820445
The only reason 1953 is standing out by its self is because the 53 235 uses the tall rotor(as do all 1954 and later).

Are you sure you have the correct "short" cap?

Dave, reading through the parts book, it reads;
29 to 34 all,(exc. - (cc,dc) 3/4 length #816774
33 to 52 all w/216 ......
53 all w/216 15/16 length #820445
53 to 54 all w/235/261 1-3/16 length #1924245
The rotor that that the truck came with and that I have since purchased for it is the 3/4. I added pics to my photobucket of the rotor installed with a cap cutaway, the shaft length, cap length and length. Sorry but I don't quit know how to separate and post them! The extra 3/16 would fill that gap between the rotor and cap contacts. If you look at the old cap contact in the rear of the cutaway you can see the wear from the arc jumping! Thoughts everyone??

In studying a distributor, in which I also cutaway the cap, I think I know what your problem is.
Distributors have a significant end play in the shaft.
When the distributor is installed in the engine the gear rests against the top of the oil pump. This pushes the gear, shaft and rotor up quite a bit. I think that if you push the shaft up, or install the distributor you will find the rotor in line with the cap terminals.

Dave, good thought! I tried it, it does bring the rotor up to just even with the bottom of the cap contacts. ( the bottom of the rotor arm is flush with the bottom of the cap contacts) Do you think that this would be enough surface? Just in case, I already ordered a pair of 820445 rotors. If anything for piece of mind and to rule this out of the equation! Stay tuned for our next exciting episode! Only here on Stovebolt.com!!!!

The distributor I was working with had the bottom of each contacts flush at the bottom, across from each other.
It sounds like your is okay.

Here are two pics, one with the shaft up and one with it down. It will be necessary to scroll to see both.

Dave, that's exactly what mine looks like! That's good!
Well since the other rotor is en-route, I'll just see what it looks like. Just 10 bucks.
I was reading through your blog earlier. Nice job! well organized.
Thanks to all who posted!
Jim