This will very likely be a rambling posting; I need advice on what to do next.
Quick history on the car and problem, the car is a ’68 L-71 convertible that I have spent the last two years doing a body off complete nut and bolt restoration (resurrection) replaced or rebuilt everything including all wiring, lighting, suspension components, fuel system, exhaust, interior you name it I have touched it. All body work prior to final painting has been completed. I have completely reassembled the car back to original condition installing all chrome, trim parts, everything that belongs in or on the car is completed.
The correct replacement (CE) engine is setting on an engine stands waiting to be completed. I have currently installed in the car a 454ci using original exhaust, intake 3/2 setup with point system. My problem is with the ignition system I have driven the car around 500 miles during this time it has died two times while driving and one time would not start after setting. Each time it has required me to have it towed. Am I sure it is in the ignition system “yes”. Each time I have checked and replaced coil, points, and condenser it starts right up runs great for about 100 miles then dies.
The following is the sequence of events and changes performed.
First time was with Delco coil, points and condenser with the original distributor the curve was set on a sun distributor machine. It started up great and the setting of dwell and timing were dead on. The car ran very strong with the 4.11 rear end I could break the tires loose in 2nd, and 3rd I didn’t need that low a gear with the torque from the engine. I changed the rear end to a 3.36 I loved it I was in hog heaven then the problems started.
First time while driving at around 45 mph the car just died I got it home and changed the coil to a MSD blaster2 the points and condenser to NAPA Echlin RR175 and CS786. Startup was immediate power was back again. The voltage checks prior to startup and after running are as follows:
Power to coil
With key on 4.4 volts
Key to start 9.9 volts
Engine running 7.9 volts
I was off and running again the next time was after driving the car a couple three different times approximately 150 miles stopping at a car cruse got ready to leave it would not start. We checked everything no fire just dead like last time.
Everyone was saying it was the coil I replace it with the original coil cleaned the points and the engine started right up. I checked voltage and did not like the reading I was getting my concern was the voltage to the coil from the resistor wiring in the new wiring harness.
Power to coil
With key on 7.24 volts
Key to start 9.97 volts
Engine running 11.29 volts
I contacted the supplier of the wiring harness in regards to the resistance in the wiring I was told the resistance should be between 1.25 and 1.45 ohms I was checking it a 1.3 ohms which was within tolerance. I was informed I should not be getting that high of voltage readings to the coil when running I had a condenser or point’s problem. I then replace the coil with a new Delco U505 coil the points with a new Delco D106P and the condenser with a Delco D204. Car restarted as it should I then checked voltage readings and they were different, the reading is as follows.
Key on 6.56 volts
Key to start 10.00
Engine running 10.99
I contacted the vendor of the wiring harness with the readings and he said the reading should be below 10 volts preferably around 7 volts when running. He requested that I send back the harness so that he could check it out. I sent him the wiring harness he checked it out and reported it to be within tolerance and that it was good. I reinstalled the harness and I was off and running again. Then yesterday after driving the car the last two days I was on my way home from a car show driving along around 60mph the engine died again. I had with me the tools to check voltage and dwell I had voltage to the coil the dwell was 30 degrees but no fire. I have the car back in the garage what do I do next?

 

I had that problem with my Chris Craft with a 350. Installed an old fashion ballast resistor and it solved the problem.

 

Have you checked the primary wire? The one from the points to the coil. I've seen them break and cause some crazy difficult to find problems. And then ground from the breaker plate to the distributor body.
When you change the points after a no start, what do the points look like? are they rough, blackend, or look like they've been really hot? The resistance wire in the harness is not so much to limit voltage as it is to limit current. (Read the ignition sticky at the top of the page. Might shed some light.)

 

I have checked the primary wire each time from end to end with no break in continuity. I have twisted and pulled but no change in continuity still had a reading of 00.0. With the primary wire disconnected from the coil I get a reading of 00.9 from coil end of primary wire to ground with the points closed, and no continuity when points are open. I have read the sticky two different times still trying to understand how the ignition works with the difference between coils.
The points the first time looked good with a minor pitting. The second set looked good with a light gray finish. The third set looked just as good with very little change in color.

To answer a PM requesting the resistance reading across the plus and minus terminals on each coil. The first coil the Delco 293 BR had a reading of 01.9 to 02.0 the second the Blaster2 had a reading of 00.7 and the current Delco U505 has a reading of 01.3 to 01.4

Thanks for the feedback I am going to be very caution on the next time out after the issues with the last failure.

 

From your description of the removed points, I'd rule out them being burned by too much current. I've seen the moving contact arm turned blue by the heat.
How about the ground from the breaker plate? Is the distributor seeing a good ground to the engine/frame?
I'd also mention that it looks like your coil primary resistance seems normal per what I've read.
As a test, you might get a ballast resistor as pictured above, and temporarily install that and see if it still quits. Years ago, (when I was playing dealer tech) we would install a secondary resistor like that and bypass the factory resistor. Like just about any wire, it's subject to being pinched, stretched, and abused.

 

I have already installed a new ground wire from the condenser mounting screw to one of the mounting screw holding the vacuum advance canister. I have a solid steel clamp holding the distributor to the block not the spring type that's setting on the shelf. I'm lost on what is going on and what to do next. I have ordered a .8 ohms MSD ballast resistor that I will try.
Thanks.

 

You need to add this if it is 68 with 68 spec harness methinks. Good luck!

 

In my research for these old style points distributors you need:

6 Volts to the coil during run
12 volts to the coil during start

I had 12 volts to the coil during run and the coil would overheat and shut down.

 

TimAT's advise in post #3 is excellent. When I was having a problem with the engine cutting out it was hard to determine if it was ignition or fuel. I extended the leads of a cheap digital volt meter so I could monitor voltage at the coil while driving. When the engine lost power I could see the coil voltage didn't vary a bit. That led me to the fuel system where I found a valve in the fuel pump coming loose.

So if you have some wire, alligator,clips, electrical tape you can rig up your voltmeter and see what happens to the juice at the coil when the engine dies.


Pete

 

Well latest and greatest I’m back on the road again. I have replaced one item at a time trying to find out what is failing. Changed the coil, still would not start. Replaced old coil changed points, still would no start. Replaced points and condenser, engine fired right up. Adjusted dwell and timing everything sounds good. The points I removed looked great light gray in color very little burning. I only had about 150 miles on the set of points and condenser prior to engine quitting. I still don’t know why I had failure in the condenser, these being the third time I have had the same problem I am trying one of the suggestion "oledave60", I have install a 0.8 ohm resister along with the current resistance wire that is in the wiring harness. I will be caring a spare set of points, condenser, and coil along with the tools to make the changes if needed.
If I have failure this time I will be changing to breaker ignition I cannot continue with this problem.