Help My distributor keeps eating rotors. It’s keeps breaking the tang that makes contact with the individual spark post. It is a 1112396 dizzy in a 57 3100 with a Th350 tranny. I’ve put two rotors in with two new caps and when removing the dizzy from the truck and spinning it you can hear and feel the tang hitting inside the cap. The cap doesn’t seem to fit as well with the rotor in it as well as it dose with out the rotor in it. Napa has verifies it is the right cap and rotor. There doesn’t seem to be much play in the shaft the rotor sits on. My next option is to replace the dizzy which I’m considering with a 1112403 which I understand is a direct replacement. Ideas or suggestions would be appreciated.
What engine do you have? I would first insure the distributor matches the engine, you appear to have the numbers for the distributor, so check against the block. There are sites online that can tell you this. Has the engine been rebuilt? Has there been a cam change? If the rotor hits the contacts inside the cap, you have the wrong rotor or cap. There is a tall cap and a short cap. Has the distributor been rebuilt?, is it it possible you have the wrong shaft? Is NAPA using the year and model of the truck or the engine to look up the parts? If your distributor matches the block and cam, you have the wrong cap and rotor.
If you have no wobble in the shaft then you have a short cap on a tall cap unit or a tall rotor on a short cap unit. Don’t feel bad about it, lots of broken caps and rotors over these many many years. As MikeE aptly stated above, match the components and all will be well.
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Does the rotor hit all the cap terminals, or just some of them? Try blackening the cap terminals with a felt tip marker and spinning the shaft by hand, then checking them to see which ones are getting the interference. It sounds like the cap isn't fitting flush onto the distributor housing- - - -maybe there's a burr on the housing or it's bent in some way? How about the spring tension on the clips that hold the cap down. Final suggestion- - - -file the rotor tip slightly to prevent interference. There's supposed to be a tiny gap between the rotor and the cap terminals, and increasing it slightly won't affect the performance of the engine. That shouldn't be necessary, however. I believe you've got a fitment problem with the cap. Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
I have had similar problems with the long and short cap and rotor arm. I would like to ask if someone could clarify the part number for Delco parts that provide a matching set. I noticed that most supplier list the rotor arms and caps but they don’t provide any matching information. I had to bend up the contact pad on the rotor arm to reach the centre electrode in the cap. So the centre pin is only contacting the very edge of the rotor arm
Thanks and best regards Chris
Last edited by ThreeSixHundred; 05/09/20197:42 PM.
If you're bending the center contact spring that far, the rotor tip is probably having to jump a huge gap to get the voltage to the plug wire terminals. That will produce a terrible miss on an uphill pull once the spark plugs get a little dirty, sort of like running a 1/8" plug gap instead of .035". The height of the distributor shaft above the breaker plate is different for the tall and short cap distributors, so just swapping caps and rotors might not solve the problem. Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
The truck has a 235 engine and the numbers on the block confirm it’ was manufactured in 57. As best I can determine the 1112396 distributor is the correct distributor for a truck with a power glide transmission. The engine was rebuilt and when I got the truck it had not been driven for some time. The previous owner indicated it did run but he hadn’t driven it much after the rebuild and hadn’t run it for a long time. I bought it without trying to start the engine. When I popped open the distributor cap after I bought it home the original rotor was broken and looked like it had been broken for some time. Napa has confirmed the rotor and cap are the correct ones for the dizzy number and have been kind enough to replace the rotors after they broke. The contact points in the dizzy cap are unevenly worn and what I mean by that is some of them have groves worn in the brass while others look pretty normal. There doesn’t seem to be any play in the dizzy shaft but I’m beginning to think this shaft might be slightly bent but it doesn’t show up when I put ruler on it and turn it. The interference shows up when the dizzy is out of the truck so ruled out the cam shaft. As I said in my original post with the rotor installed the cap has a bit of play in it that isn’t there when the rotor is out.
That 2396 unit is for a 54 with automatic transmission. The 2403 was 55-63 all, and service replacement for 46-63. Should take a D306 cap (1924248), D105P points, and a D405 rotor. The 2305 uses the same cap, point set and rotor.
If you have a 57 block, get a 2403 distributor, have it rebuilt so it works properly.
Nice clean lubricated advance weights on nice tight solid pins, all clean, new components, check point tension and get it on to a sun machine or Allan machine to set the dwell and confirm the advance is coming in when it should and is all in when it should be.
Yes, the 2400 is really what you want. There are more of them around, parts availability is better. I have never run an automatic with a 235 or 261 but I see no reason why the 2400 would present any issues as it was used behind the cast iron power glide motors. That being said, the fact is that these distributors are really really old, and most are really laden with thick grease under the point plate and shaft assembly, or have broken or worn pins, or broken springs for the advance weights, or there is so much rust and crud in and on the advance weights that the mechanical advance is just not working or working poorly, or the shaft is just so worn that the wobble makes setting the dwell or point gap so unpredictable as a useless exercise.
From there, the questions go why is my motor running poorly, why do I not have a little power, why does the motor run badly on acceleration and then try to solve it with new coil, wires, plugs, when the issue is really with the distributor.
I have two NOS 2400 distributors. Neither of them came up to specification when I first got them. Both needed cleaning and adjusting and they were new and never used. A rebuilt distributor with a correctly functioning mechanical advance makes a world of difference, at least in my experience. So go to the trouble of getting a replacement unit, pay close attention to the condition of the lobes, no rust, and have it rebuilt.
I agree, the Sun machine is a really great tool. I purchased it a couple of years ago up in New York where it had been sitting in a warehouse since the late 1980s. Was apparently owned by RCA at one time who used it to developed ignition modules for the big OEMs. It was in outward great shape. I bought it out of necessity as the man who was rebuilding my distributors retired and if I wanted to continue to play with these early motors (I am in my late 50s), I would have to invest in some of the more professional tools so I bit the bullet. I cleaned it up, and rebuilt the electronics. Mark Sanders at Paramount Distributors is the guru of these machines and has all the parts to get one back into operating condition. Without him and his parts, this machine would still be DOA.
Update, got a rebuilt distributor, installed rotor and cap and everything spins as it should, no interference. I believe the old distributor was the problem with why it was eating rotors. Not exactly sure why but rebuilt distributor is tighter and has less play than the old one.
So..... I was not sure if the timing was right and do not have a BB on the fly wheel to confirm TDC. Before I installed the distributor I put a PSI/Vac gage on the number 1 cylinder and rotated the crank until I’m right between pressure and Vac. This leaves both number one cylinder push rods loose while the number 6 has one tight and one loose. When rocking the crank back and forth the number one rocker arms move very little while the number 6 intake and exhaust open and close. I think this is number one firing position I then align the the oil pump tab on the distributor and reinstalled with the rotor in the 5 o’clock position, seated it and then rocked the rotor slightly to insure oil tad was aligned. Does this sound right to you guys?
