GT6 MkIII Mis-fire - ignition coil?

[Jon Nield]

My 1971 GT6 Mk III has recently started to mis-fire whilst motoring, but only after running fine for the first 15-20 minutes, so I'm guessing this is a problem with the HT coil and related to heat build up, based on my reading of the various articles on this subject on the forum. It's currently fitted with a Lucas DLB 105 and a ceramic ballast resistor.

 

According to Rimmer Bros info, DLB 105 (part no. GCL110HP) is a high performance 12v coil for Mk I & II - presumably this is a 3 ohm coil and should not be used in combination with the ballast resistor.

 

On the basis that I stick with ballast resistor, is the correct coil one of the following:

 

a) Ignition Coil - Standard - 6v ballasted (GCL132)

Ignition Coil - High Performance - 6v ballasted (GCL132HP)

 

and, if so, am I better off with the HP version?

 

[dougbgt6]

On the basis that coils are more expensive than ballast resistors, why would you stick with the ballast resistor?

[djn]

Try a "Red Rotor Arm" which I believe you can get from the club shop. 

[Pete Lewis]

Dlb 105 is a non ballasted 3 ohm coil the solution is simple delete the bast ceramic amd run it on full 12volts

 

by using the ballast you are halving the designed HT voltage and this will reduce the spark to very small

 

dont use any spark plugs with an R in the suffix or the misfire gets even worse

 

If you have an electronic set of points many do not like a ballasted feed even though some have a

operating range of 6 to 18 volts with a low battery the ballast feed is often below this and misfires

begin.

[Last_Vitesse]

Having not long gone through a similar exercise on one of my cars, which doesn't have a ballast coil.

Order of fault location would be,

1. Check the coil primary resistance if its 3 ohms then its not a ballasted coil, you need to dump the ballast resistor or fit the correct 6 volt coil.

2. Change the rotor arm for a red one.

3. Change the Dizzy cap for a good quality one.

4. Make sure the plugs are ok and gapped correctly

5. check or replace the ht leads the lead from the dizzy to the coil can very often cause weak spark when hot (especially if you are using a 12 volt coil with a 6 volt ballast resistor)

 

For me it was the "rotor arm" the quality of some of these after market parts has been very poor.

Have a look here http://www.distributordoctor.com/red-rotor-arms.html

Regards Mike

[Jon Nield]

Thanks all. Finally got it sorted. Ballast resistor now bypassed and root cause problem tracked down to a deteriorating HT lead. All leads now renewed and engine running sweetly (at last).

 

Regards,

 

Jon

[AtRo Racing]

I am using the Bosch Blue coil with the internal ballast resistor. I have eliminated the ballast resistor that is located near the coil. This coil will throw a spark that is 1/2 inch long.

 

Robbie