[GMCnet] spark plug questions, please
Ek_Lektro
not sure which ones to buy...
When i pulled a few of the old ones out, the gaps on them ranged from .45 to .70...
no wonder it was running crappy? (Can the gap change that much over time?
or is it more likely that the previous mechanic botched the gapping job?)
So i checked the cross reference on my GMC Motorhome International Parts Interchange Index (circa 1998!)
and for my '76 455, these are all listed as compatible:
AC R46SX with .80 gap
Bosch WR10FCZ with .80 gap
Champion RJ18YC6 with .60 gap
AutoLite 847 with no gap spec listed
in this same index, i can see that for other GMC years, the recommended gap can range from .40 to .80...
Considering that this '76 engine was supposedly rebuilt back in 2002,
is it safe to assume that they rebuilt the same engine, and that the same spark plug specs apply?
Bottom line, what's the conventional wisdom say about best plugs to use,
(and/or which to avoid), and of course, the recommended gap spec?
OK, thanks much for any info....
Greg
SolarSonic / LosAngeles
PS: No surprise, I've noticed that some of the parts numbers in this '98 index are starting to become obsolete
at AutoZone, etc. Wondering if this is mainly due to the parts in general getting more scarce over the years,
or if perhaps its just time for a new Parts Interchange Index?
Anybody know if GMCMHI has been keeping the parts index up to date?
If so, i think it'd be time to subscribe again... $30 or so....?
Sure got my money's worth out of the last one.. LOL...!
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Andrew
Ek_Lektro wrote on Wed, 06 July 2011 12:56
> Anybody know if GMCMHI has been keeping the parts index up to date?
My copy (arrived in the mail a few days ago) says "Spring 2011, supersedes Spring 2010", so YES to that.
There are 30 or so replacements listed, depending on year and engine. I'm guessing you have a 455, 1975-1977...
The new AC part number is R46SZ (0.080 gap).
The Champion and Bosch numbers are still listed as current.
The Autolite number is still current, still no gap listed.
Also, NAPA Champion (CHA) 0.080 gap, part # 66.
--
1973 Sequoia 260 (since 2011)
Savannah, GA
Thomas Phipps
Most people have abandoned the .80 gap size. It is hard on the rest of the spark system. I suggest .45. "Your mileage may vary."
Tom Phipps,
Dennis Sexton
Greg,
You can look at an application on the GMC photo site.
Ek_Lektro wrote on Wed, 06 July 2011 12:56
> Well, its been a while.... and its definitely time for a new set of plugs!
> not sure which ones to buy...
> When i pulled a few of the old ones out, the gaps on them ranged from .45 to .70...
> no wonder it was running crappy? (Can the gap change that much over time?
> or is it more likely that the previous mechanic botched the gapping job?)
>
> (and/or which to avoid), and of course, the recommended gap spec?
>
> OK, thanks much for any info....
> Greg
> SolarSonic / LosAngeles
>
> PS: No surprise, I've noticed that some of the parts numbers in this '98 index are starting to become obsolete
> at AutoZone, etc. Wondering if this is mainly due to the parts in general getting more scarce over the years,
> or if perhaps its just time for a new Parts Interchange Index?
> Anybody know if GMCMHI has been keeping the parts index up to date?
> If so, i think it'd be time to subscribe again... $30 or so....?
> Sure got my money's worth out of the last one.. LOL...!
--
Dennis S
73 Painted Desert 230
Germantown, TN
James Hupy
they now do, do not set your plug gaps at .080". .045" - .050" is now
accepted to be the correct gap for a HEI equipped 455 or 403. Plug choice is
kinda up to the individual, although I prefer Bosch Platinum with the small
center electrode.
Jim Hupy
Salem, OR
78 GMC Roayle 403
Jim Galbavy
There are many reasons that a p/n becomes obsolete. ....and that doesn't necessarily mean that the item or part is obsolete. I found that p/n's for automobile or aircraft can change for no other reason that the manufacturer has changed or upgraded their computer data base and now the old number is not compatible with the new system. So the change.
I would recommend that you renew you membership in GMCMHI and get the latest data.
jim galbavy
'73 x-CL // ANNIE
Lake Mary, Fl
John Wright
mostly current, but I need to update again with the latest numbers.
http://www.gmcmhphotos.com/photos/data/5237/Spark_Plug_Application_Gu.pdf
JR Wright
On Jul 6, 2011, at 1:56 PM, Ek_Lektro wrote:
> Well, its been a while.... and its definitely time for a new set of
> plugs!
> not sure which ones to buy...
> When i pulled a few of the old ones out, the gaps on them ranged
> from .45 to .70...
> no wonder it was running crappy? (Can the gap change that much over
> time?
> or is it more likely that the previous mechanic botched the gapping
> job?)
>
> So i checked the cross reference on my GMC Motorhome International
> Parts Interchange Index (circa 1998!)
> and for my '76 455, these are all listed as compatible:
> AC R46SX with .80 gap
> Bosch WR10FCZ with .80 gap
> Champion RJ18YC6 with .60 gap
> AutoLite 847 with no gap spec listed
>
> i
Gene Dotson
Ek_Lektro wrote on Wed, 06 July 2011 13:56
--
Gene Dotson
74 Canyonlands
www.bdub.net/Motorhome_Enhancements New Windows and Aluminum Radiators
Len
This is a list of plug that I have found that should work in the 455 & 403
engines. If you have others that work you can add to the list.
Brand 455 Eng Style 403
Eng
Style
AC/Delco R46SZ Std. Same
AC/Delco 41-818 Plt. Same
AC/Delco AC#7 Plt. Same
Autolite AP847 Plt.
847
Std.
Bosch 4023 Plt.
4022
Plt.
Bosch 7921 Std.
7920
Std.
NKG 4536 Std. Same
NKG 7293 Iridium Same
--
J.R. Wright
GMC Great Laker
GMCMHI
TZE Zone Restorations
77 Eleganza II (For Sale)
75 Avion (Under going Frame up Restoration) On Location at Florida Space
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Len and Pat
78 Kingsley, The Beast II with dash lights that work
Fallbrook, CA
http://www.gmcmhphotos.com/photos/showgallery.php?cat=4375
Ken Burton
AC Delco #7. Gap them at .040". Run them for 100,000 miles and change them again.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
Phil Swanson
The new #7 is not the same plug as before. It has the old Champion style tip....... garbage. Try to find the old #7s much better plug.
Phil Swanson
Ken Burton
philipswanson wrote on Thu, 07 July 2011 09:26
> The new #7 is not the same plug as before. It has the old Champion style tip....... garbage. Try to find the old #7s much better plug.
>
> Phil Swanson
I have heard that but have never seen one. I put some in several years ago and will not worry about ever changing plugs again. I heard Dick Paterson is recommending a new plug by a different manufacturer. I do not know what that one is.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
Phil Swanson
If you go and buy a new RF #7, you will see what I am talking about. The old ones are almost indestructable and I am still running those thanks to Jim K.
Phil Swanson
Don Adams
Anybody have a picture of the old #7 tip?
philipswanson wrote on Thu, 07 July 2011 09:26
> The new #7 is not the same plug as before. It has the old Champion style tip....... garbage. Try to find the old #7s much better plug.
>
> Phil Swanson
--
Don
67 Datsun 2000
78 Suzuki 400
bill schurman
I'm running Autolite # 847. Runs just fine.
William S. Schurman
P.O. 773325
Steamboat Springs, CO (Ski Town USA)
at the foot of Rabbit Ears Pass
970-846-4212
'78 Palm Beach TZE 168V100258
'90 SHO
'66 912
> To: gmc...@temp.gmcnet.org
> From: dj.a...@att.net
> Date: Thu, 7 Jul 2011 14:22:40 -0500
> Subject: Re: [GMCnet] spark plug questions, please
>
>
>
>
John Wright
recomends a new plug.
See at bottom of notes
John Wright
See note at bottom of chart.
http://www.gmcmhphotos.com/photos/data/5237/Spark_Plug_Application_Gu.pdf
JR Wright
On Jul 7, 2011, at 2:24 AM, Ken Burton wrote:
A.
powerjon wrote on Thu, 07 July 2011 17:03
> Original Delco #7 plugs are no longer available.
>
> See note at bottom of chart.
>
>
> http://www.gmcmhphotos.com/photos/data/5237/Spark_Plug_Application_Gu.pdf
>
> JR Wright
Does the chart apply to points and condenser ignition systems?
--
'73 23' CanyonLands
John Wright
Read the note under the plug chart. Point systems generally requirer
smaller gaps than HEI systems
JR Wright
On Jul 7, 2011, at 6:13 PM, A. wrote:
>
>
> powerjon wrote on Thu, 07 July 2011 17:03
>> Original Delco #7 plugs are no longer available.
>>
>> See note at bottom of chart.
>>
>>
>> http://www.gmcmhphotos.com/photos/data/5237/Spark_Plug_Application_Gu.pdf
>>
>> JR Wright
> Does the chart apply to points and condenser ignition systems?
> --
A.
powerjon wrote on Thu, 07 July 2011 20:01
> Yes,
> Read the note under the plug chart. Point systems generally require smaller gaps than HEI systems
>
> JR Wright
> On Jul 7, 2011, at 6:13 PM, A. wrote:
>
> >> See note at bottom of chart.
> >>
> >> http://www.gmcmhphotos.com/photos/data/5237/Spark_Plug_Application_Gu.pdf
> >>
> >> JR Wright
> > Does the chart apply to points and condenser ignition systems?
> > --
My apologies. I read the note under the chart but not very well I guess. Will set mine for .040. Thanks much.
--
'73 23' CanyonLands
J A Holland
We are running Autolite 847's with 45 gap in our '78 with a 403 ~
~ Joe ~
--
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