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Good to hear you got it figured out. Frustrating how a simple fix could have been taken care of way back and just got missed.
Guess one plus to all this is that everything else should be pretty much sorted out and will be good cruising from here on out.
Not to wish headache on anyone, but there were some take aways on this for future issues I may run into and I do learn from others.
Thanks to everyone who had the fingers(and thumbs)on this.
I thought for sure I had this intermittent miss figured out, it’s back! I’m going to replace the cap and points even they have about thirty miles on them. There are a few places on the cap and point faces that look like light arcing, I’ve got to start the elimination somewhere.
Since this returned (same symptoms as the original ) I’ve put on new spark plug wires, re checked the plugs, checked the distributor grounding and re checked timing-dwell.
Any recommendations for quality points?
KC
Mallory used to make good ones but don't know if they still make them. Never liked ACCEL the spring tension is too high causing the running block to wear fast requiring frequent adjustments.
Update, I replaced the plug wires, omned and cleaned the plugs. Replaced the points, condenser and set the timing to 36 and dwell to 30. The miss is a bit better so it’s leading me to an electrical issue. The hesitation- miss is more noticeable around 2700 to 3000 rpm. The distributor has been rebuilt-checked by a person known to be reputable on this site but it seems like it may be related to mechanical advance. I’ve looked at the mechanical advance many times with the timing light and they have never failed to advance. That being said, we all know that a moving car under load is a very different situation.
I also put the timing light lead on every spark plug wire and they seem consistent.
I welcome your input!
KC
I checked each plug with the engine running(idle), the spark looked pretty healthy and consistent from wire to wire. I did notice that the arc did move from the front of the metal tip to the back. This was consistant on all wires.
I put foam on all of the wires in an attempt to isolate any cross “talk”, I don’t think that is the issue but just playing elimination at this point.
KC
<snip>I did notice that the arc did move from the front of the metal tip to the back. This was consistant on all wires.<snip>
What do you mean by that?
On the ground or “side electrode” there was some movement from front to back of the spark. On the drawing it would be from th3 red to green mark direction. I didn’t know if this is normal?
I did get a test drive in with the insulation on the plug wires and no improvement. I didn’t think that was the issue but had to eliminate the possibility. The only glimmer of light is the possibilities are getting pretty small. I took the valve covers off and had someone spin the engine while I watched, everything looked correct. Is it likely that lifter is the issue? I didn’t really go that direction as the car has ran very well, just intermittent.
KC
I’m just about out of things this miss could be. It looks like my cloth wrapped resistance wire that goes to the coil is original. Could insulation be gone and affect the coil voltage? How can this be tested and what value should it be? I’m kinda down to something related to the distributor. For those who haven’t followed this thread the distributor has been overhauled.
KC
I’m still trying to run down this miss. I checked the voltage at the coil with the engine off and read 7.3 volts (positive side of the coil and ground to engine). I checked the voltage with the engine running and it read 13.3 volts on the positive side.
This is a stock 71 LS5 with the original wiring harness. These readings sound correct but shouldnt they be reverse? I do have the original cloth resistance wire and it’s on the poisitive side along with the start wire.
I thought the positive should read about battery voltage with the key on and drop to a lower voltage after start?
KC
Higher voltage (12V) should only be while the starter is engaged.
That wire comes from the "S" terminal on the starter solenoid IIRC. "R"
Should be less at all other times as long as the key is in "run".
Last edited by leigh1322; Feb 13, 2025 at 08:32 PM.
Higher voltage (12V) should only be while the starter is engaged.
That wire comes from the "S" terminal on the starter solenoid IIRC.
Should be less at all other times as long as the key is in "run".
Any idea what could be causing the higher voltage? Shouldn’t the voltage drop when the starter dis engages?
Any idea what could be causing the higher voltage? Shouldn’t the voltage drop when the starter dis engages?
Yes it should drop.
This says yellow and white go to neg side of coil.
Pos side to points.
Yellow goes to S on starter. OOPS! it goes to "R" on starter! Bad memory.
Does that look right on your car?
Last edited by leigh1322; Feb 13, 2025 at 08:33 PM.
Hhmm, if I’m interpreting the schematic correctly it shows the distributor wire going to positive side of the coil. I thought I checked a schematic (1971)when wiring and it showed the coil wire going to the negative side? I have the starter wire, ignition wire and condenser wire on the positive side.
