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914World.com _ 914World Garage _ spark plug gap for a six conversion

Posted by: rfuerst911sc Dec 26 2010, 05:37 AM

My GT clone has a 1978 911SC 3.0 with stock internals. The ignition distributor was reworked by Jerry Woods to maximize performance with the Weber carbs. I have a Mallory HI-IV ignition box with a MSD Blaster coil. Plug wires are OEM braided with Bosch copper plugs. Car runs quite well but I'm curious what spark plug gap is suggested ? I've read anywhere from stock to .060 and everything in between. If I remember correctly I currently have them just a little larger than stock. So what are you guys using for plug gaps ?

Posted by: J P Stein Dec 26 2010, 06:58 AM

I ran .050 gap.

A couple other comments that you may take or leave as desired.

I used the MSD Hi vibration coil. It is potted and can be used in any attitude.
Oil filled coils should be mounted upright lest they spray oil all over God's creation.

Big plug gaps need big voltage. Normal wires oft times can't handle the increased voltage (36000+ v). The big gaps "burn through" the rich mixtures due to Webers and prevent plug fouling.

I found NGK copper plugs work best. Plugs used to be "one is as good as another" to me....no more.

This was hard won data from some years back. Bout 6 months of dicking around with a motor that just didn't run to my expectations.

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