Spark plug gap

Chumley · May 25th, 2008, 11:48 AM

I have a '73 350 with HEI. What do you guys gap your plugs at with this motor?
Chumley

Jim's rare 80 · May 26th, 2008, 04:56 AM

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.

Jim.

joe_padavano · May 26th, 2008, 06:41 AM

Agreed. Gap on an HEI should be 0.060" - 0.080"

Pghstarsky · May 26th, 2008, 07:20 AM

Damn...that's a big gap. Would that be the same for a 72 350 with HEI upgrade?

88 coupe · May 26th, 2008, 11:03 PM

My book says .040 for all '72 Olds.

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

Norm

Chumley · May 27th, 2008, 02:03 PM

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.

Warhead · May 27th, 2008, 06:16 PM

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

J-(Chicago) · May 27th, 2008, 06:20 PM

Quote:

Originally Posted by Warhead

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.

OLD SKL 69 · May 27th, 2008, 07:00 PM

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.

Chumley · May 27th, 2008, 09:25 PM

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.
Chumley

May 25th, 2008, 11:48 AM	#1 (permalink)
Chumley Registered User Join Date: Dec 2005 Posts: 217	Spark plug gap I have a '73 350 with HEI. What do you guys gap your plugs at with this motor? Chumley

May 26th, 2008, 04:56 AM	#2 (permalink)
Jim's rare 80 Registered User Join Date: Feb 2007 Posts: 209	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. Jim. __________________

May 26th, 2008, 06:41 AM	#3 (permalink)
joe_padavano Super Moderator Join Date: Mar 2007 Location: Northern VA Posts: 4,396	Agreed. Gap on an HEI should be 0.060" - 0.080" __________________ Joe Padavano 64 Jetstar 88 Conv 66 442 L-69 Conv 68 W-30 69 H/O 69 442 70 W-30 72 442 84 Custom Cruiser 86 Caprice wagon (w/307 Olds)

May 27th, 2008, 07:00 PM	#9 (permalink)
OLD SKL 69 Registered User Join Date: Jan 2007 Location: Long Island, New York Posts: 306	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. __________________ Darrell 1971 Cutlass Supreme

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May 26th, 2008, 07:20 AM	#4 (permalink)
Pghstarsky Senior Member Join Date: Sep 2007 Location: Pittsburgh Posts: 102	Damn...that's a big gap. Would that be the same for a 72 350 with HEI upgrade?

May 27th, 2008, 02:03 PM	#6 (permalink)
Chumley Registered User Join Date: Dec 2005 Posts: 217	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.

May 27th, 2008, 06:16 PM	#7 (permalink)
Warhead Registered User Join Date: Mar 2008 Location: Phx, AZ Posts: 311	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

May 27th, 2008, 09:25 PM	#10 (permalink)
Chumley Registered User Join Date: Dec 2005 Posts: 217	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. Chumley

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