Corvette JABO

Does anyone know what the resistance value for the Nichome wire that goes to the positive side of the ignition coil on a 1969 Corvette?

I also have a 62 Vette with a 70 LT-1, I have been having an issue at high RPM’s with the ignition breaking up around 5,250 RPM and up. I had installed an MSD Blaster coil model 8222 for higher voltage over the stock coil about 1.5 years ago. I recently tried installing MSD points model 110128 with the 32 oz spring and the MSD 100108 condenser. These points really mad a difference at high RPM, the car just keeps pulling hard. I had several miles on the new point and the car ran like butt, I thought at first I had a bad condenser and installed another set of point and condenser but the points immediately burnt up. To make a long story short I took out the MSD Blaster coil.

With the help of MSD Tech Support I realized that the internal resistance of the MSD coil is allot lower than the factory GM coil. My factory ballast resistor on the 62 has a resistance of 0.3 ohms and this allowed too much current to the Blaster coil. MSD sells a ballast resistor for their Blaster coils with a resistance of 0.8 ohms. I imagine that the MSD breaker point also have a lower internal resistance than the parts store replacement points and by the time I installed the MSD points I was flowing too much current for the MSD coil to handle. I had to go back to the factory replacement coil and I am using the MSD points and condenser and it is running well, I just cannot hit the higher RPM’s, I think this is due to the factory replacement coil. I will probably buy another MSD coil but I will also need to buy the MSD ballast resistor.

So back to the 1969 Vette. Usually, when I make a performance modification I do it to both the 1962 and the 1969 at the same time. So in the 69 I have the same MSD Blaster coil and I have installed the same MSD points with the 32 oz spring and condenser. The 69 performance is fantastic, pulls really hard without any breakup at high RPM’s. The problem is, I do not know what the resistance is on the Nichrome resistance wire that runs to the positive side of the coil. Am I flowing too much current to the coil and am I going to take out the coil and points on this car also?

David

Bandit54

I don't know if the '69 is the same as my '68 or not I have been going through all kind of problems with my ignition system. During trouble shooting process I have checked the lead wire to the coil from end to end and had resistance of 01.3 ohms. The information from the wiring harness manufacturing was that the resistance should be 01.25 to 01.45. I don't know if this helps or not but your posting makes sense to me. I have so far burnt up two MDS Blaster2 coils, I'm in the process of installing the 0.8 ohm resister today and see if this corrects my problem. You might want to check my posting "Ignition problems, help, advice, dynamite"
Good luck

Corvette JABO

Thank You

7T1vette

The '68 car did not have a resistance wire...it had a ballast resistor that mounted to the firewall.

The '69-'74 cars had the same resistance wire and ignition (points) system, I believe. In '75, C3's went to HEI distributor system.

The resistance wire for my '71 SB car is listed as 1.35 ohms (fixed; in-harness). The mating ignition coil had 1.77-2.05 ohms Primary resistance and 3000-20,000 ohms Secondary resistance.

Corvette JABO

But if you add a 0.8 ohms to your already 1.3 ohms this will give you 2.1 ohms which could reduce the current too much. Have you tried to reinstall the stock coil just to see if it is drivable? I know that MSD recommended a resistance of only 0.8 ohms for the Blaster coil.

Easy Mike

67 was the last year for ballast resistors. 68s have the resistance wire.

7T1vette

I had a '68 many years ago, and my recollection was that it had a ballast resistor. I could be mistaken...

augiedoggy

my 74 had a ballast resistor is well along with points which I've since replaced with a tach drive hei unit. 75 was the first year for HEI....(look how much it improved power) I bet the blaster has the internal resistor built in