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[GMCnet] AC spark plug for our 78 403 [message #326295]

Thu, 23 November 2017 18:55

BobDunahugh

Messages: 2465
Registered: October 2010
Location: Cedar Rapids, IA

Karma: 11

Senior Member

When the PO put AC plugs in. R46SX plugs were installed. According to a shop manual that I have. The correct plug for the 403 is R46SZ. I'm not up on the meaning of the X, and Z. I'm sticking with the AC plugs. Bob Dunahugh
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Re: [GMCnet] AC spark plug for our 78 403 [message #326296 is a reply to message #326295]

Thu, 23 November 2017 19:34

emerystora

Messages: 4442
Registered: January 2004

Karma: 13

Senior Member

According to plug information I have the R46SZ replaced the R46SX. The SX's were gapped for .080 and the SZ was gapped at .060. Only difference. Just bend your tab on an SX and make it work. However the current thinking is that a .038 gas is better with the hei system.

Emery Stora

> On Nov 23, 2017, at 5:55 PM, Bob Dunahugh wrote:
>
> When the PO put AC plugs in. R46SX plugs were installed. According to a shop manual that I have. The correct plug for the 403 is R46SZ. I'm not up on the meaning of the X, and Z. I'm sticking with the AC plugs. Bob Dunahugh
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org

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Re: [GMCnet] AC spark plug for our 78 403 [message #326302 is a reply to message #326295]

Fri, 24 November 2017 10:36

mrgmc3

Messages: 210
Registered: September 2013
Location: W Washington

Karma: 2

Senior Member

FYI ACDelco still offers the R45S plug. This is gapped at .040 and "45" is one heat range colder than the R46SX.

Chris Geils - Twin Cities / W Wa 1978 26' Kingsley w/ very few mods; PD9040, aux trans cooler, one repaint in stock colors, R134a, Al rad, Alcoas, 54k mi

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Re: [GMCnet] AC spark plug for our 78 403 [message #326306 is a reply to message #326295]

Fri, 24 November 2017 11:30

BobDunahugh

Messages: 2465
Registered: October 2010
Location: Cedar Rapids, IA

Karma: 11

Senior Member

The 46 heat range seemed hot to me. But the plugs that I remove looked the perfect color as to heat. They have about 12,000 miles on them. I'll put new ones in anyway. And I want to index them trod the combustion chamber to alien the flame front. Not a big thing. Just me being anile with details.

________________________________
From: Bob Dunahugh
Sent: Thursday, November 23, 2017 6:55 PM
To: gmclist@list.gmcnet.org
Subject: AC spark plug for our 78 403

When the PO put AC plugs in. R46SX plugs were installed. According to a shop manual that I have. The correct plug for the 403 is R46SZ. I'm not up on the meaning of the X, and Z. I'm sticking with the AC plugs. Bob Dunahugh
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Re: [GMCnet] AC spark plug for our 78 403 [message #326307 is a reply to message #326306]

Fri, 24 November 2017 12:20

powerjon

Messages: 2446
Registered: January 2004

Karma: 5

Senior Member

Gentlemen,
There is a spark plug chart that has been published in the GMCMI parts interchange and available here:

http://www.gmcmhphotos.com/photos/data/5237/Spark_Plug_Application_Guide.pdf

Altho this was done in 2013 there has been no real updates in plugs available since then.

JR Wright
GMC Great Laker MHC
GMC Eastern States Charter Member
GMCGL Tech Editor
GMCMI
78 GMC Buskirk 30’ Stretch
1975 GMC Avion (Under Reconstruction)
Michigan

> On Nov 24, 2017, at 12:30 PM, Bob Dunahugh wrote:
>
> The 46 heat range seemed hot to me. But the plugs that I remove looked the perfect color as to heat. They have about 12,000 miles on them. I'll put new ones in anyway. And I want to index them trod the combustion chamber to alien the flame front. Not a big thing. Just me being anile with details.
>
>
> ________________________________
> From: Bob Dunahugh
> Sent: Thursday, November 23, 2017 6:55 PM
> To: gmclist@list.gmcnet.org
> Subject: AC spark plug for our 78 403
>
>
> When the PO put AC plugs in. R46SX plugs were installed. According to a shop manual that I have. The correct plug for the 403 is R46SZ. I'm not up on the meaning of the X, and Z. I'm sticking with the AC plugs. Bob Dunahugh
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org

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J.R. Wright
GMC GreatLaker
GMC Eastern States
GMCMI
78 30' Buskirk Stretch
75 Avion Under Reconstruction
Michigan

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Re: [GMCnet] AC spark plug for our 78 403 [message #326309 is a reply to message #326295]

Fri, 24 November 2017 13:39

JohnL455

Messages: 4447
Registered: October 2006
Location: Woodstock, IL

Karma: 12

Senior Member

I thought R45S was correct --are those discon? My understanding was the x was long reach electrodes

John Lebetski
Woodstock, IL
77 Eleganza II

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