Hi R66 - As I said, the voltage regulator ground wire was loose enough that I could twist it back and fourth. I did that a few times to make sure there was no paint under the loop connector and then tightened it to the point where I could not move it. The only other variable was that I removed the distributor/coil shielding. I just went for a 40 minute test drive without issue. ????? Could that reg ground not being 100% tight have caused this? Is it possible that the shielding could be causing this type of problem?

Thanks,
Rick

 

Rick,
That shielding can be a real trouble maker...I have mine, permanently, on a shelf. The back of the shielding can snag/cut the pink wires going to the ignition coil...not good. The ignition coil, itself, can ground to the shielding if the coil is not correctly oriented (poles parallel to the firewall) and/or if the plastic insulator is not installed in the interior top of the shielding. Plus, the shielding doesn't allow air flow to aid in cooling the ignition coil. It's there for "show" only...park in storage somewhere.

 

double post...

 

Thanks Leif! I'm taking your advice and leaving it off for a while. If after several weeks of hopefully no issues I may put it back on just to get the data point that identifies it as the root cause....

 

The loose ground wire could contribute to your problem, but that is only my opinion. To test it, disconnect the wire and see if the engine will run. I believe it will as the ground wire is needed for operation of the voltage regulator and alternator, thus the charging system would be affected, but not the ignition as you still have power from the battery. One of the EE types here on the forum may need to correct this redneck opinion.
Leif has very good advice. While the shielding is off, check the wires behind the shielding on the firewall for nicks and cuts. Might be my eyes, but it appears there is a nick in the red wire coming down near the coil - it may just be to the choke.
There is an added red wire off of the positive battery terminal, is there an amplifier box hidden somewhere or where does that red wire go? You might want to trace it down. What electrical devices in the car do not work or work properly? Was a kill switch added?
Just ideas, may be of no help.

 

Your Mallory Unilite may require a differently rated resistor than factory...

If you had the factory distributor, it's easy to get the proper resistor.
The factory resistors were 1.8 ohm "blue stripe" resistors. You can find these at Summit and all the regular Corvette vendors (and a whole host of other places I'd imagine). They were the resistors used for '65-'67 (non-TI). The one you have is definitely a general replacement. (When measuring resistance, my 1.8 blue stripe actually measures 2.3 but doesn't seem to have any issues at that resistance. Lower resistance leads to increased points wear.)

BTW, I like the old points design: they're reliable, inexpensive, and simple.

 

Hi 67:72 - Thank you sir! I'll figure out the Mallory replacement and get one to have on hand in case. Meanwhile I'm looking for a good replacement for the Mallory distributor and coil as well. Hope you saw that my last 40 minute test drive without disty shielding was without issue. The gremlin is inconsistent in that I can go on 3 or 4 test drives with no issue then suddenly it may die 1 to 3 times during a 10 minute skirmish....I've had the shielding off and on so many times without really taking note so I don't have any data of issue with or without shielding until now.

Data Point 1 - 40 minute drive without shielding - No Issue

 

R66 - Your eyes are good ! That RED wire with the nick is for the choke as you surmised. The posted picture is from a few weeks ago. I discovered that nick, taped it and then as part of all the engine running issues I've had since I bought this car I completely removed the choke and wrapped up and tucked that wire away.

 

Funny you should point this out. I just had an issue with this very thing last week. I was doing some engine work and was using a remote starter button to bump the engine over and while doing so noticed SPARKS flashing from under the shroud. HMMM! Pulled the shield and found that the metal had somehow come into contact with one of the Pos coil wires and had actually chafed through the insulation. The gap in insulation was quite large and prominent. Very easy to spot. I installed a new ring terminal, added 2 layers of heat shrink tubing and readjusted the leads. Have not yet re-installed the shroud and may not do so per this discussion as I have no radi interference.
Big questions are ---how long has this thing been flashing under there and how close was I to a spontaneous engine compartment fire?
Always sumpin!
Eddie

 

It appears the red wire from the battery positive terminal does go to some type of device tucked under the fender. Can you determine the purpose of the device or follow the wire from it to find out if it is part of the ignition system? You can disconnect the wire from the battery and see what no longer works if you cannot determine what it is for.
What aftermarket accessories have been added to the car? Are there any added accessories like a modern radio?
Are there any electrical devices that don't work?
You may want to buy a battery terminal boot to put over that positive terminal due to the close clearance to the overflow tank. Although the tank is not grounded, the coolant in the tank can conduct electricity and provide a path to the block and the ground wire on the block back to the battery. Probably never happen, but why gamble for a couple of $$. A redneck will make a sleeve out of an old bicycle inner tube to insulate the terminal. Yea, I am one of those guys.

 

Good morning R66

Aftermarket accessories - Vintage Air only

Radio is original and works however the entire power antenna assembly is missing - there is a toggle switch behind the center dash that I assume was at some point put in for the antenna up/down. Likely when the vintage air was installed and the side plate was replaced with an aftermarket for the A/C duct. This replacement side plate does not have a provision for the antenna switch.

A forum member suggested that I search for a potential KILL switch. This toggle switch that I found and assume is antenna up/down is not a KILL switch for sure. Car starts regardless of switch on or off.

What does not work are Battery Gauge, Clock, Windshield Wipers, Sig Lighter, Odometer and the trip meter, It appears that the Trip Meter reset cable is missing but the mounting bracket under the dash is there

Tucked under fender - Red wire from battery goes to some sort of plastic sealed container - shown in pictures - I have no idea what this is. It traces to an entry point on the far right of the A/C housing on the firewall. It appears that a hole was punched in the fiberglass housing then sealed with a black sealant

There is also 2 original connectors that are not connected to anything. I've taken pics of them as well

Man, what a mess I have purchased.....

Today I'll buy Battery Terminal Protectors from Amazon

 

That's a thermal circuit breaker, could be part of the vintage air system

Tom

 

You should seriously consider rewiring the car with a new harness in the engine room and interior. Its a good bit of work, you can do it yourself, and it will inure to your long term benefit. The time it will take to decipher and repair if possible what a prior owner did will get you well far along with a new harness. Everything will work, and a bonus, the car will not burn to the ground.

Dan

 

I also spoke to MSD support. The support tech stated that my issue is a momentary loss of ground. If it were the coil then it would take time to cool down and not start immediately as it does.

 

All the more reason to remove all of this nonsense and begin again. Not hard. Not a complicated car. Two makers of beautiful exact replacement harnesses exist to help. Install a new harness with a rebuilt Delco points distributer. If you want to eliminate points use an Lectric Limited points substitute (rather than Pertronix).

The Mallory ignitions are just OK for racers and those who believe the red box looks cool and makes the car run better. But they add a layer of unnecessary complication and between it and the lousy wiring you have an unreliable car.

Again...forget about making sense and reliability from something that can be neither.

Dan

 

I took a look at the available harnesses. Seems that all the corvette dealers sell them. Can you make a specific recommendation on engine bay and interior harness to buy? I assume it will be specific to small block convertible without A/C, right? I just realized that as I have vintage Air that alternator is on the left side so maybe a with air harness is what I need for the engine bay?

Thanks,
Rick

 

I have no idea what this device is. Have you checked it for power with both the key on and off? What color are the wires and can you tell where they go? Maybe someone else has seen a device of this type.



Power antenna switch on R66 probably the same as your car - maybe.

I understand your last test run seems to have indicated you have resolved the issue, so this may be a waste of your time.
Ron

 

R66 - Ron, I sent you a private message

 

Rick-
Our friend Ron is looking to save you money. Admirable cause but bad idea in my opinion. If this was a car for which no harness is available that would be one thing. But Lectric Limited & American Autowire both make outstanding harnesses, take your pick, decide on price, availability, shipping cost otherwise it is irrelevant who you buy from.

I would sooner take a carb or alternator completely apart and fix it before I replaced it. But not unlike old patched up plumbing in an old house old patched wiring in an old car will never be entirely fixed until replaced. Even if you chased every clue or direction Ron dutifully supplied above you will still have crappy wiring full of splices, butt connectors, likely mis-matched wire size and other problems that will eventually rear their ugly heads in the form of a failure to run, darkness and smoke.

There is no badge of honor awarded to those who drive cars with bad wiring nevertheless made to work.

Dan

 

Hi Dan, I 100% get and agree with your point! I am looking at harnesses now. I suspect that with my vintage air and the alternator on the left side that a harness with air is in order so that the Alternator RED is on the left to mount to the alternator. I'm not a wiring expert but I am capable of routing and connecting once I learn what the correct routs and connections should be....

My car does not have backup lights