| [GMCnet] The Correct Spark Plugs Mean A Lot [message #247801] |
Fri, 18 April 2014 01:00  |
BobDunahugh
Messages: 2465
Registered: October 2010
Location: Cedar Rapids, IA
Karma: 11
|
Senior Member |
|
|
I got interested in what the correct spark plug to use in my 6,000 Watt Onan that's in our GMC. As the two 78 Royale's both appeared to have the wrong plugs. The first clue was that all the plugs were too short on the threaded portion of the plugs. And I found 3 different plug numbers installed. Called 4 GMC owners. Asked them to go check their Onan spark plugs. None of them had plugs that matched anyone elses plugs. Then put something out to the form. Got some list of plugs to use. When to Auto Zone with list in hand. Found some of the plugs had the tapered sealing surfaces that were on the interchange list. Those are definitely wrong. Checked our GMCMI parts book. So to make absolutely sure that I had the correct plug that Onan called for in our generators. I ordered two spark plugs at my local Cumminns/ Onan dealer. So the absolute CORRECT spark plugs are Champion brand RH12. Now I have heard comments made at times that this, or that brand of plugs aren't very good. Whene
ver I've dug into plug failures. It's always been a case of the wrong plug for that application. There are lots of different plug numbers. There is a big reason why. In the next day or two. I'[ll list some of the plug number. And what the numbers, and letters mean. And explain how to properly index your spark plugs to the combustion chamber. For the best fuel efficiency by having a cleaner flame front at the time of ignition. I index all my plugs to the combustion chamber.Bob Dunahugh Member GMCMI78 Royale4 Real COPO Yenko's
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
|
|
|
|
| Re: [GMCnet] The Correct Spark Plugs Mean A Lot [message #247821 is a reply to message #247801] |
Fri, 18 April 2014 10:24  |
powerjon
Messages: 2446
Registered: January 2004
Karma: 5
|
Senior Member |
|
|
This list has been developed over a number of years and is current. APU plugs start on second page. It will also be available on Gene’s site.
<http://www.gmcgreatlakers.org/gmcing/tech_docs_gl/SparkPlugApplicationGuide.pdf>
I am going to have a difference of opinion other than Bob’s on the indexing of spark plugs and this is my PERSONAL OPINION developed in the 20+ years that I was racing stock, modifieds and gassers, alcohol dragsters and funny cars and both nitro classes and again their can be many differing opinions. The indexing of spark plugs is a valuable method of extracting the last bit of power out of a gasoline powered engine and some alcohol motors such as circle track engine. We used to do it in the stock, super stock and modifieds that we ran. That attention to detail can mean a few tenths in a quarter mile or lap time on a road course or circle track. Will it provide a noticeable difference in how our coaches run and use fuel, probably not measurably. Just gap the plugs and run them. Modern FI units give our coaches the best technology to increasing fuel milage and spark control. As for a plug being too short in an 1800 rpm industrial motor, I personally wouldn’t sweat it, I would be more concerned if the plug extended into the combustion chamber. As for onans the addition of a electronic spark control is the best addition over points you could add to your onan, easier starting and smoother running.
JR Wright
GMC Great Laker MHC
GMC Eastern States
GMCMHI
78 GMC Buskirk 30’ Stretch
1975 GMC Avion (Under Reconstruction)
Michigan
On Apr 18, 2014, at 2:00 AM, Bob Dunahugh <yenko108@hotmail.com> wrote:
>
>
>
> I got interested in what the correct spark plug to use in my 6,000 Watt Onan that's in our GMC. As the two 78 Royale's both appeared to have the wrong plugs. The first clue was that all the plugs were too short on the threaded portion of the plugs. And I found 3 different plug numbers installed. Called 4 GMC owners. Asked them to go check their Onan spark plugs. None of them had plugs that matched anyone elses plugs. Then put something out to the form. Got some list of plugs to use. When to Auto Zone with list in hand. Found some of the plugs had the tapered sealing surfaces that were on the interchange list. Those are definitely wrong. Checked our GMCMI parts book. So to make absolutely sure that I had the correct plug that Onan called for in our generators. I ordered two spark plugs at my local Cumminns/ Onan dealer. So the absolute CORRECT spark plugs are Champion brand RH12. Now I have heard comments made at times that this, or that brand of plugs aren't very good. Whene
> ver I've dug into plug failures. It's always been a case of the wrong plug for that application. There are lots of different plug numbers. There is a big reason why. In the next day or two. I'[ll list some of the plug number. And what the numbers, and letters mean. And explain how to properly index your spark plugs to the combustion chamber. For the best fuel efficiency by having a cleaner flame front at the time of ignition. I index all my plugs to the combustion chamber.Bob Dunahugh Member GMCMI78 Royale4 Real COPO Yenko's
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
J.R. Wright
GMC GreatLaker
GMC Eastern States
GMCMI
78 30' Buskirk Stretch
75 Avion Under Reconstruction
Michigan
|
|
|
|
| [GMCnet] The Correct Spark Plugs Mean A Lot [message #248008 is a reply to message #247801] |
Sun, 20 April 2014 19:10 |
BobDunahugh
Messages: 2465
Registered: October 2010
Location: Cedar Rapids, IA
Karma: 11
|
Senior Member |
|
|
Did some checking on spark plugs for our Onan generators in the last few days. I only looked at Champion as a base line. As Champion is the company that Onan went to for plugs to meet the parameters of what their engines required. I think that this is an important point here. As Onan did extensive testing of their own produces. Thus selected the components that would be best suited for the longevity of the products they produced. In the Winter 1996 issue number 54 of the GMCMI newsletter. ( Thanks, Billy Massey for that copy. ) It stated clearly that the correct plug was a Champion RH12 plug. Or as Champion stock number 537. Both numbers refer to the same plug. That still stands today. Also listed was Champion number RH10. This plug is a hotter range plug. But isn't avalible from Cummings/ Onan dealers. If you're burning oil. And that's causing issues. The RH10 will help with oil fouling of the plugs. As stated below. The Onan part number for that RH12 is 167-0262. If you wa
nt to cross reference to another brand of plug. Use the Champion plug numbers listed above ONLY. There are no other Champion plugs that will match the Onan specifications closer, or better. I see no reason to use any other Champion plug. Or other brand plug that doesn't cross reference to RH12/537. Remember. there are other brands of plugs that will cross reference. These plugs are listed as will work. For me. Onan sells only that Champion plug for their application. You can get that plug anywhere. For me. I'm going with the plug that the Onan engineering staff liked. No one knows their product better than them. Remember. Engines that are used to run generators, water pumps, and such things. Operate in conditions that don't exist anywhere else. This running at slow, and constant speeds. Bring on issues with the combustion chamber, and to spark plugs that exist no where else.Bob Dunahugh Member GMCMI78 Royale4 COPO Yenko's
I got interested in what the correct spark plug to use in my 6,000 Watt Onan that's in our GMC. As the two 78 Royale's both appeared to have the wrong plugs. The first clue was that all the plugs were too short on the threaded portion of the plugs. And I found 3 different plug numbers installed. Called 4 GMC owners. Asked them to go check their Onan spark plugs. None of them had plugs that matched anyone elses plugs. Then put something out to the form. Got some list of plugs to use. When to Auto Zone with list in hand. Found some of the plugs had the tapered sealing surfaces that were on the interchange list. Those are definitely wrong. Checked our GMCMI parts book. So to make absolutely sure that I had the correct plug that Onan called for in our generators. I ordered two spark plugs at my local Cumminns/ Onan dealer. So the absolute CORRECT spark plugs are Champion brand RH12. Now I have heard comments made at times that this, or that brand of plugs aren't very good. Whene
ver I've dug into plug failures. It's always been a case of the wrong plug for that application. There are lots of different plug numbers. There is a big reason why. In the next day or two. I'[ll list some of the plug number. And what the numbers, and letters mean. And explain how to properly index your spark plugs to the combustion chamber. For the best fuel efficiency by having a cleaner flame front at the time of ignition. I index all my plugs to the combustion chamber.Bob Dunahugh Member GMCMI78 Royale4 Real COPO Yenko's
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
|
|
|
|
| Re: [GMCnet] The Correct Spark Plugs Mean A Lot [message #248014 is a reply to message #248008] |
Sun, 20 April 2014 19:41 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
|
Senior Member |
|
|
Bob,
Have you yet done the Pertronix ignition upgrade to your Onan? I'll bet it
will combat your oil fouling problem as well as a step hotter plug. It's
really hard to believe how much better an Onan runs with ol' Lawrence
Gaskins' bright idea implemented.
Ken H.
On Sun, Apr 20, 2014 at 8:10 PM, Bob Dunahugh wrote:
>
>
> ...Also listed was Champion number RH10. This plug is a hotter range
> plug. But isn't avalible from Cummings/ Onan dealers. If you're burning
> oil. And that's causing issues. The RH10 will help with oil fouling of the
> plugs.
...
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
|
|
|
|
| Re: [GMCnet] The Correct Spark Plugs Mean A Lot [message #248020 is a reply to message #248008] |
Sun, 20 April 2014 20:46 |
cbryan
Messages: 451
Registered: May 2012
Location: Ennis, Texas
Karma: 3
|
Senior Member |
|
|
Bob,
With reference to the Onan 6000 watt generator spark plug replacement in many of our motorhomes, the following cross reference to the RH12 Champion. I well realize that the RH12 may be the best choice as the R&D was done with that number, but maybe folks might be wanting a cross reference chart.
It was an internet listing, so your mileage may vary, as well as availability. Here's what the internet says:
AC Delco 43LS
Accel 166
Autolite 4316
Autolite MP4316DP2
Autolite 216
Champion stk 537
Denso W16LS
Eyquem 500A
Motorcraft AL5
Splitfire SM021F
The Autolite is often on sale, though I don't have any real preference. I have had good luck with most of these brands. Bad luck with none, if you don't count a few broken insulators due to ham handed operator error on installation. I plead the fifth amendment.
Carey
Carey from Ennis, Texas
78 Royale, 500 Cadillac, Rance Baxter EFI.
|
|
|
|
| Re: [GMCnet] The Correct Spark Plugs Mean A Lot [message #248030 is a reply to message #247801] |
Sun, 20 April 2014 21:26 |
 |
Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
|
Senior Member |
|
|
| BobDunahugh wrote on Fri, 18 April 2014 02:00 |
I got interested in what the correct spark plug to use in my 6,000 Watt Onan that's in our GMC. As the two 78 Royale's both appeared to have the wrong plugs. The first clue was that all the plugs were too short on the threaded portion of the plugs. And I found 3 different plug numbers installed. Called 4 GMC owners. Asked them to go check their Onan spark plugs. None of them had plugs that matched anyone elses plugs. Then put something out to the form. Got some list of plugs to use. When to Auto Zone with list in hand. Found some of the plugs had the tapered sealing surfaces that were on the interchange list. Those are definitely wrong. Checked our GMCMI parts book. So to make absolutely sure that I had the correct plug that Onan called for in our generators. I ordered two spark plugs at my local Cumminns/ Onan dealer. So the absolute CORRECT spark plugs are Champion brand RH12. Now I have heard comments made at times that this, or that brand of plugs aren't very good. Whene
ver I've dug into plug failures. It's always been a case of the wrong plug for that application. There are lots of different plug numbers. There is a big reason why. In the next day or two. I'[ll list some of the plug number. And what the numbers, and letters mean. And explain how to properly index your spark plugs to the combustion chamber. For the best fuel efficiency by having a cleaner flame front at the time of ignition. I index all my plugs to the combustion chamber.Bob Dunahugh Member GMCMI78 Royale4 Real COPO Yenko's
|
Bob,
While I don't doubt your data at all, both the BF 4.0s that I have here have Champion H-10 plugs.
I just went to the Champion site and got RH18Y for those.
Then I plugged in NH 6.5 (they didn't list 6.0) and got RH8C.
This is just great, I do completely agree with you about the importance of having the correct spark plug, but I'm pretty sure that the H-10s are too cold.
Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
|
|
|
|
| Re: [GMCnet] The Correct Spark Plugs Mean A Lot [message #248054 is a reply to message #248020] |
Mon, 21 April 2014 11:10 |
A Hamilto
Messages: 4508
Registered: April 2011
Karma: 39
|
Senior Member |
|
|
FYI...
I looked up the Champion part number for their 8H (Onan 4kW) and got 587. The Champion part number for their RH12 (Onan 6kW) is 537.
The interweb says my local O'Reilly's has both in stock, and they are $1.99 plus tax each.
None of my other local auto parts stores have those Champion part numbers, but they do cross reference to others that are in stock.
|
|
|
|
GMCforum
Search
Help
Register
Login
Home
