The wear I see always shows up on the distributor contacts and appearance-wise the rotors look fine. But I always replace them together for good measure.
I haven’t noticed any wobbliness of the shaft when I change the rotors.
I do live in Indiana and it can get a humid during spring/summer. I haven’t had any rough running during rain or anything like that though. (But carrying a spare is a good idea!)
These posts are kind of confusing the way they’re laid out, I’ve been replying to the replies so stuff is out of order. (It’s my first time on this forum)
How often is about every 4 to 5 thousand miles. I don’t drive the car a lot. The reason I change them is when the car decides not to start!!! It will run fine and then just decide that it’s not going to fire up one day.
I was just hoping to improve the dist/rotor life span thinking maybe I was using the wrong spark plugs or something.
This is a very strange problem and some things are very odd. No way should the cap and rotor need replacement at 5k miles intervals.
I’m having a hard time seeing the cap and rotor being the cause of a no-start condition.
To do this would mean the rotor and cap terminals would have to be absolutely fried beyond recognition.
My feeling is that this no-start is due to something else and the restart is conincidental.
Ignition switch or ignition module intermittent fault is at work here; or something. It would take more than burned terminals to cause a no-start.
Any moisture inside the cap when it fails to start?
If the contacts inside the cap get pitted and nasty looking, that’s meaningless and will not hurt a thing. Of course they get pitted! 40,000 volts does not care how pitted they are…Like Ok said, now and then, the ROTOR would break down and an arc would burn through the rotor down to the center shaft…Also, since the “igniter” moves with the VACUUM advance, the wires, after a while, can break INSIDE their insulation right at the igniter unit. To check, gently pull on the wires and watch where they enter the igniter. If the insulation stretches easily, the wire inside is broken…
This engine came with R44S AC plugs. The wide gap version, used with HEI ignition is R44SX.
It’s interesting to note the most popular engine option that year was the 300hp 350 cu.in. engine. The 400 cu in engine was rated at 265hp, and burned regular fuel…
There is no correlation with moisture and the no start problem. And you’re right that the contacts are not burned terribly, just a small pit on each contact with soot around it.
Read above and I described how I’ve once replaced a control module when new dist/rotor failed to allow starting. This spring when getting it out of mothballs I was getting no spark even after replacing the d/r again. I was about to take the control module in to have it tested when I decided to try re-making the contacts on either end of the control module. (My reasoning was that since I had left the car sit for nearly two years this time and maybe the contacts had gotten oxidized/corroded.) So when I put it all back together it fired up a like a champ. I am sure the problem is not where the ignition and other wires plug into the distributor, because I messed with those several times with no success while trying to fire her up this spring.
The next time the car fails to start and if there is no spark check for battery voltage at the B+ terminal at the distributor. There should be power in both the RUN position and when the engine is being cranked over by the starter motor.
No power during cranking would cause a no-spark condition and this would likely be an ignition switch fault. (not uncommon and certainly not at 40 years old)
Make sure the carbon button beneath the coil is in good shape and installed correctly; you should get a new one with each distributor cap.
I’ve seen many that have been installed upside down, while the car will still run you’re not getting anywhere near the voltage through the ignition that you should.
How do I check whether there is power? And am I correct to assume you mean the ignition switch to mean the mechanism in the steering column that engages when the key is turned?
To run the voltage test ok4450 refers to, just unhook the B+ wire on the distributor and test with a multimeter, red probe on the wire, black probe to negative battery terminal or ground, either one. There should be full battery voltage there key on and cranking. If there’s not, suspect the ignition switch.
I will also suggest trying different plugs. I am not a fan of Bosch spark plugs because I have never gotten decent performance out of them. I would try ACDelco plugs in this engine. I have always had good luck with them.
You have other issues you are not addressing. I have had the same cap and rotor on my '80 Vette for 10 years and drive it alot. Starts everytime. You are buying quality parts, right? What type of fuel delivery system do you have? Whats your timing set at?
Save your self some time, take the car to an automotive electrical shop and have them test the system. They should be able to tell you if it was upgraded properly, if not what needs to be done. You can deside wether you want to do do it or let them do it. I ripped the computer system out and went back to a pre 70"s igntion, no morew problems
Can’t figure out why this post got bumped up…The last post was in April…
Anyway, the high-voltage contacts in HEI caps can be expected to be burned and pitted. That does not hurt a thing. The 40,000 volt system laughs at stuff like that. They can be burned down to nubs… The only weakness this system had was sometimes the high voltage burned through the center of the rotor and found a path to ground that way. The two wires connected to the ignition module could break internally (inside the insulation) because of the constant movement of the breaker plate…If you pulled the wires gently, you could see the little hourglass form in the insulation as the wire stretched…