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Old May 25th, 2008, 11:48 AM   #1
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Spark plug gap

I have a '73 350 with HEI. What do you guys gap your plugs at with this motor?
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Old May 26th, 2008, 04:56 AM   #2
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73's didn't have HEI. The closest is a 75 for HEI. According to my book, It's R-46SX plugs gapped to .080, and timing at 20B.
Hope this helps.
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Old May 26th, 2008, 06:41 AM   #3
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Agreed. Gap on an HEI should be 0.060" - 0.080"
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Old May 26th, 2008, 07:20 AM   #4
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Damn...that's a big gap. Would that be the same for a 72 350 with HEI upgrade?
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Old May 26th, 2008, 11:03 PM   #5
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My book says .040 for all '72 Olds.

No reason to use more, unless cylinder pressures and/or fuel mixtures have been changed.

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Old May 27th, 2008, 02:03 PM   #6
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The motor is a '73, and had HEI added at some point. I'm assuming it's very low compression and small valves. The old plugs were all at .035, but I'm going to go .040 with the new plugs. I run my big block Chevy at .060, and have not had any problems, but I know you can't compare apples to oranges.
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Old May 27th, 2008, 06:16 PM   #7
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Gap your HEI plugs no more than .060".
I usually go .045-.050".
The "book" says .080 for 76-77 HEI's, it creates more problems than it solves. JMO
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Old May 27th, 2008, 06:20 PM   #8
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Quote:
Originally Posted by Warhead View Post
Gap your HEI plugs no more than .060".
I usually go .045-.050".
The "book" says .080 for 76-77 HEI's, it creates more problems than it solves. JMO
Jim
I agree.
I also believe that Olds sent out a recall/correction page about the .080 gap issue. Changing it to .060.
I remember writing it on my fan shroud years ago.
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Old May 27th, 2008, 07:00 PM   #9
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I have a 69 350 and took out the points distributor and changed over to an HEI. I gap my plugs at 040 and it runs great. Hope that helps.
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Old May 27th, 2008, 09:25 PM   #10
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Thanks for all the input guys, I gapped them at .045, now I just have to put the new wires together, install, and see how it goes. I wish I had a '72 or older motor. The car is a '72. In '73 everything changed dramatically performance wise.
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Old May 27th, 2008, 09:25 PM
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