MSD Spark Plug Gap

[Buckskin7T7V]

I just installed a MSD-6A unit in the 77.
I am running NKG XR-5 spark plugs. I was hoping that someone out there, knows a good spark plug gap to change to. Taking the plugs in and out, is not much fun.
I know you should increase the gap to get the most out of the unit. I am now at the stock setting of .045.
Thanks

 

[72Slydog]

Check the MSD Ignition website. They have installation available for download. Suggested spark plug gap is related to the engine compression. They suggest starting with initial setting of .050 to .060". You can increase this in .005 increments until you are satisfied with the performance

 

[Stingray72]

Let us know what you end up with, Buckskin. I recently installed a 6AL, and I've been wondering the same thing.

Thanks.

 

[Buckskin7T7V]

Well I spent two hours pulling the plugs and regapping them from .045 to .060. The car runs good. I will leave it and get back to you.

 

[69redvette]

I went to the MSD site and asked the same question and they gave the same answer 72slydog did. I never knew that you could open up the gap with an MSD ignition to as high as .060" for an engine with up to 10.5:1 compression. I'm going tp try it tomorrow. Maybe it will help solve my fouling plug problem. I have a 350ci with Trick-Flow Twisted Wedge heads, Victor jr intake, Holley 750, Comp Cams solid lifter, with Hooker Super Comp headers and sidepipes that just loves to foul plugs. Been playing with carb adjustment, jet size and timing for years. Does anybody think this will help or am I barking up the wrong tree?

 

[Stingray72]

It very well may help. Opening the gap on the plugs results in a hotter spark because more voltage is required to arc across the larger gap. You could also try a set of plugs with a higher heat range.

 

[Buckskin7T7V]

MSD suggests to use one heat range COLDER plug. I had just installed NGK XR-5 (stock heat range for the 1969 heads I have on my 77) so far they are working fine. I also installed a Edelbrock Air/Fuel ratio gage and I am running 13:1. I will slowly rejet to 14:1 but I do not want to get too lean. I am running close to 10:1 on regular gas. Eldebrock Performer with a Holly 4175/0-9895 Spreadbore.