69 427/390 Ignition Issues

[Salvatore I.]

I have been trying to get my 427/390 to run consistently without much success. Not to make this a huge message, some background: I wanted to move away from points and condenser & bought the Breakerless SE unit and had 2 coils crap out on me. I then swapped the Breakerless SE unit into a 67 small block 327/350 and the SE unit has worked flawlessly.

I returned the 69 BB ignition to the original set up and bought what I thought were the best set of points on the market, the Blue Streak brand for points, their rotor and their condenser just about 2 months ago. Yesterday, I had the car on the road for 2 miles and started having ignition issues...(I know that this sounds crazy, but it was like a cylinder miss intermitantly when the car was under a load, like going from 1st to 2nd or into 3rd!) I then replaced the plugs and replaced the spark plug wires with the same ignition issue...By the way, the plugs were beautiful with a mild sandy color indicating to me that the plugs are of the right heat range... I then proceeded to pull the distributor cap and until I replaced the points and the condenser, had the same intermittant ignition condition...When I inspected the points, I saw that they were burned...In just about 2 months, the points burned up....but the car started and ran...only under a load did it buck and feel like a dead miss....

Can I get some guidance on what to look at next and what could possibly be causing the ignition to burn up?

[Michael M.]

Re: 69 427/390 Ignition Issues

Make sure that all of the ignition connections are tight. Sometimes, if a ground is a little loose it will interrupt the ignition. If it is only under load, it may have to do with the torque/twisting of the engine causing a bad ground to exhibit itself. Just a shot in the dark.

[Duke W.]

Re: 69 427/390 Ignition Issues

Check that the primary ignition circuit resistance wire in the harness has not been bypassed. Measure voltage at the coil + terminal, key on engine, off with the points closed. It should be about half battery voltage. If it's battery voltage, the primary resistance wire has been bypassed, which causes too high primary current that will quickly burn the points and fry coils.

You will find the resistance wire in your CSM wiring diagram.

Duke

[Steven C.]

Re: 69 427/390 Ignition Issues

If the primary wire to the points is at 12 volts (instead of less as Duke mentioned); or to troubleshoot the problem:

Two easy ways, put a ceramic ballast resistor in line to the primary points wire, or

Get an internally resisted coil (gasp...Ford).

I had a similar problem on a '59 Pontiac, intermittent, turned out that the stock ballast resistor was deteriorated. I solved the problem by doing both of the above suggestions!

Steve

[Joe L.]

Re: 69 427/390 Ignition Issues

Duke and Sal-----

Yes, someone may have replaced the original special resistor wire with "garden variety" wire. The original resistor wire had a light-colored, fabric- like "sheath" which covers the wire. This wire connects to the coil. Make sure that one of the wires going to the coil looks like this. If not, that's a "clue".

[Terry F.]

Re: 69 427/390 Ignition Issues

Sal, at start up your engine uses the full voltage of the battery to run the coil. This provides a hotter ignition momentarily while cranking the engine. After you let the ignition switch pop back to the run position, it should drop the voltage through a resistor. If the resistor has been bypassed, it will eat the points. I believe a bad condensor might cause similar problems but I am not certain of that. If your wiring harness has been messed with, I would look real hard at it. Terry

[Salvatore I.]

Re: 69 427/390 Ignition Issues

Joe

I do have a special cloth-covered wire at the coil...does this line have a resistor in the circuit, like I have in-line on the 67? With the 67, there is a pink line at the coil running thru the ballast resistor...is it the same on the 69 BB design?

Also, where does this cloth line from the coil connect to...does it run to the starter?

Thanks....!

[Joe L.]

Re: 69 427/390 Ignition Issues

Sal-----

There is no ballast resistor used in 68+ Corvette applications. The resistance wire replaced the earlier ballast resistor.

[Salvatore I.]

Re: 69 427/390 Ignition Issues

Joe

What is connected at the other side of the cloth wire that runs from the coil?

Thanks!

[Joe L.]

Re: 69 427/390 Ignition Issues

Sal-----

There are actually 2 "cloth-covered" wires which have a single connector at the coil (+) terminal. One of the wires goes to the "R" terminal of the starer solenoid. If I recall correctly, the other goes to the ignition switch. I'm not 100% sure about the latter, though.

[Salvatore I.]

Re: 69 427/390 Ignition Issues

Duke

There are 2 large ground cables on my 69 427...one at the battery box that connects the ground cable right to the frame and the other at the side of the starter that connectes the frame to the engine...Last night I noted that the engine ground cable had been connected from the frame directly to the starter bolt and not to the engine as in the assembly manual...Do you think that this is creating a weak ground?

Sal

[Duke W.]

Re: 69 427/390 Ignition Issues

I can't tell you the exact ground cable configuration for a '69, but a ground problem is not likely to be the cause of your problem.

Try my previously recommended voltage checks and report the results.

Duke