plugs gapping question ?
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Joined: Feb 2006
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From: terrebonne quebec
plugs gapping question ?
i,ve got an msd pro billet distributor with an msd 6al box and a matching coil from msd giving me apparently 48,000 volts . my question is what should i use in terms of spark plug gap . the engine temp is always arond 180 . the heads are aluminum and the comp. ratio is arond 9.7 to 1 and i,m using 94 octane gas ? 
Melting Slicks
Joined: Mar 2006
Posts: 3,456
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From: Piedmont Va
St. Jude Donor '11-'12-'13,'19-'20
I just switched from Points to HEI. The factory specs for points gap was .035. For HEI for 1975 was .060, and for 76-82 was .045. My new AC R44TS were factory gapped at .045 so I installed them at that setting. At least one other forum member advised to go to at least .040
Melting Slicks
Joined: Oct 2002
Posts: 2,317
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From: St Louis MO
plugs gapping question ?
With the very high output of the MSD-6, it has absolutely no problem firing across a larger gap. Smaller gaps are only necessary for high compression ratios or for supercharged applications. Since the spark duration is so short, a longer gap lights the fire more reliably since it touches more gasoline molecules, and is especially helpful at partial throttle settings, in other words, better mileage at cruise. I've had good luck with setting the gaps to .060 and have been doing so for the last 25 years with the MSD and capacitive discharge type ignitions.
Cheers,
Larry
Cheers,
Larry
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Joined: Feb 2006
Posts: 58
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From: terrebonne quebec
thank you guys . i was already running .050 but was afraid of cracking the positive electrode insulation with more .i,m going to give it a shot to .060 and see what's happening , cause it's a pain in the --- to remove some of these angled plugs , in particular that # 7 . cheers
