Point based tune-up tips
First a more detailed explanation of the point based ignition. It might help.
On the point driven ignitions, regular running voltage for the coil was 6 volts. This is so the points wouldn't fry in a few miles. A resistor wire or ballast resister was used to drop the voltage. This is between the ignition and coil. The - side of the coil went to the distributer and points. You can't measure the voltage drop caused by the resister if the points aren't closed or the wire isn't hooked up to the coil. The current has to be flowing at the actual use rate to measure voltage drop across a resister wire or ballast resister correctly.
Make sure you get voltage to the coil. Usually the resister/ballast is good or bad, not much in between.
To help starting, a hotter spark was used. Full 12 volt to the coil. Usually a wire from the outboard connection of the starter solenoid to the coil. This wire was 'hot' when the starter was turning.
There are 3 wires connected to the solenoid besides the big power wire from the battery on my 66. The purple wire on my 66 starter solenoid is the starter wire. The one with power in the start position. This goes to the small S terminal on the starter solenoid. The inboard one next to the block if there are two. If your starter only has one small terminal, this is the wire to use to get the starter to engage.
Solenoids for later model cars do not have this outboard wire connection. It wasn't needed with HEI ignitions. HEI uses straight 12 volt all the time. When changing starters and Solenoids, make sure you get the right one. One with 2 small terminals is needed for points.
The resistor wire went from the firewall plug to the outboard (Fender side) connection of the solenoid. Then a regular wire from the solenoid outboard connection to the coil. Both of these wires connect to the same post The solenoid when the starter was turning energizes this post with 12 volts. When not starting, the voltage only came via the resistor wire, thus about 6 volt run. This gives 6 volt run, 12 volt start
Other things to
watch out for with point ignitions.
1. The Points. Get points that have a screw/nut to connect them to the wire. Some use only spring pressure to hold the wire. I can't remember how many of them I replaced on customers cars after they had been to a cheep tune in the 70's. They have poor connections and tend to loose contact at high rpm or with corrosion over time.
Don't touch the contact areas on the points. Oils from you fingers or a shop rag may insulate the points and cause them to not work. Keep contact areas clean.
2. Always replace the condenser when changing points. The round cylinder that connects to the points and is bolted down to the distributer plate. Sometimes it was built into the points. The condenser is a capacitor and helps to keep the arcing down when the points open and keep the break point consistent. A bad condenser will either short and cause no or intermittent spark or let the timing wander a few degrees.
3. Don't get
carried away tightening the screws on points/condensers.
The plate often strips before the screws.
4. Do use a good grade of point grease on the shaft where the point follow runs on the distributor shaft. A little, not a lot. Clean off the old grease before adding the fresh stuff. Grease kept things smooth, but mostly kept the follower on the points from wearing down and changing the dwell.
5. Always buy good brand names for electronics. We always used AC/DELCO or Niehoff. I Can't find Niehoff in Dallas area. Don't know if they exist anymore.
6. Adjust the dwell THEN a final check on the timing. Changing the dwell changes the timing.
7. Check the vacuum advance and make sure it doesn't leak. Make sure the mechanical advance is working and not sticky.
8. For best results, check Dwell and adjust every 3-4000 miles. Tune up at 10000.
9. Make sure you have the correct plugs. Double check if the Plug has an R, or resistor. HEI ignitions used resistor plugs but most point ignitions did not.
10. Corrosion/build up on the distributor terminals can reduce spark on point based ignitions. You don't always have to buy a new cap. A good small flat point screw driver applying pressure the right way can pop the build up off in many cases.
11. Is the rotor turning? Is it in the right place? You can have a perfect tune up and the car still not run if the timing chain (V8) has slipped or the distributor gear is worn/slipping.
Is the coil working?
Test coil firing. Disconnect the negative wire on the coil, the one that goes to the distributor. Hook up a wire to the negative side of the coil. Remove the coil ignition wire from the distributor cap and put the exposed metal end of the wire close but not touching to an un-painted metal part on the intake. Within 1/4 inch. With power on contact the wire to ground and remove. The coil should make a spark and you should see it jump from the ignition wire end to the metal. Careful, don't shock yourself. This is not a guarantee of a good coil or wiring may be a problem. A bad coil may still pass this test, but under load not function well.
Disconnect point/dist wire from coil. Then:
Make sure you have power to coil. Turn on key and put test light on + wire side. Is there power.
Check coil negative side now. Is there power getting through the coil with key on? If not replace coil.
Turn engine until points are closed. With ohm meter check point/distributor wire for resistance between ground on engine and the point wire. Should be none. If infinite or very high, wire is broken or points aren't closing or have oil/contamination on them. Your own body oil from your fingers can cause a problem on the point surface.
Turn engine until points are open. Check wire to ground resistance again. Should be infinite, no flow. If still showing no resistance, you have a wire grounded or the condenser is bad.
Re-connect point/dist wire to coil.
Take out condenser and check between wire and condenser body for resistance with ohm meter. Should be infinite or very near so. If showing low or no resistance, replace, even if new.Check resistance of coil to cap plug wire. If older, did it crack/break inside during the tune up?
I better stop here before I get carried away anymore. HEI ignitions are a lot less work when doing tune-ups.
If the HEI module is blown, it is usually caused by High voltage feeding back. You need to fix the problem. If you don't your new module will fry in a few weeks also. Some causes in the most common order from my experiences.
Coil leaking voltage
Bad rotor letting voltage through.
Bad cap with too much build up/resistance on contacts.
Bad spark plug wire or
Bad driving habits. In one case a customer drove his pickup as if it were a diesel. He would shift from 1st to 4th at low rpm. Heavy throttle and low rpm was the result. The extreme cylinder pressure soon caused a lot of high voltage feedback through the whole system. Wires, modules and even the ignition switch was fried.
When plugs, wires and caps go
they have high resistance. The electrical spark has to go
somewhere and when it can't go where it is supposed to, it can fry
In the late 70's the modules where $50 and the coils $15, caps $8 and rotors $1.50. Not checking these parts ate profits in a hurry when you had to put in a second module free. Always buy good quality ignition parts. Cheap ones will fry the module.
The old point based coils were 10-15KV with a gap of around .032 on the plugs. Electronic ignitions went to around 25KV+ (my after market is 50kv advertised). Plug gaps went to .045 to .06 and "resistors" were added to the plugs to help handle the higher voltage without burning the tips of the plugs off.
When a coil goes bad it can drive you crazy. Anything from no spark, to spark looks good, but car wont run well no matter what you do. Be careful when hooking a voltage tester up to a coil. Even small voltage can create a spark when you remove the power.
HEI coils. I will try to explain what to look for on bad HEI coils, but it is a knack and experience. look for burn areas on the plastic insulator. How bad, well that is the judgment call. The HEI coils keep firing, but when they start to go bad, they bleed high voltage.
When coils go bad and start shorting sometimes you can hear the static on your AM radio, if you have AM anymore.