| Re: [GMCnet] Mufflers? [message #341948] |
Sun, 24 March 2019 12:27  |
BobDunahugh
Messages: 2465
Registered: October 2010
Location: Cedar Rapids, IA
Karma: 11
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Headers radiate a huge amount of heat under the entire coach. Verses the stock manifolds. It's all in the surface area of each. Muffler size also plays into this heat transfer issue. Wrapping any exhaust components will greatly reduce their service life. In 2008 we were in Lake Havasu City Az. Early Aug. The outside temps were around 115 degrees. With the gen running the roof A/C. Our 78- 403 Royale's GVW is just under 12,000 lbs. Plus we where pulling a trailer with a car on it. Total GVW was at just over 17,000 lbs. We have no extra venting above the front wheels. Pure stock exhaust that includes gas tank heatshields between the tail pipe, and both gas tanks. I had made, and installed new heatshields that were longer, and taller then the stock ones. Then attached them to the floor above. Used the stock engine fuel pump with a boost pump at the rear for the carb.
I now have 2 pumps at the rear. That are mounted on the outside of the frame. Along with the 2 filters, relay, and steel line to just behind the left front tire. This feeds a Howell/GM EFI.
2 years ago I installer 2 Magna flow series 40 muffler copies. The Magna Flows are about $78 each. The copies are $33. on Amazon. There're about 8 inches shorter then stock.( Thus less heat transfer to the bottom of the GMC. ) With a big plus of being made of a heavy welded steel construction. It's all in the details. Bob Dunahugh 78 Royale Iowa
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| Re: [GMCnet] Mufflers? [message #341955 is a reply to message #341948] |
Sun, 24 March 2019 19:38  |
amansfield1104
Messages: 80
Registered: August 2009
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> On Mar 24, 2019, at 12:27 PM, Bob Dunahugh via Gmclist wrote:
>
> Headers radiate a huge amount of heat under the entire coach. Verses the stock manifolds. It's all in the surface area of each. Muffler size also plays into this heat transfer issue. Wrapping any exhaust components will greatly reduce their service life. In 2008 we were in Lake Havasu City Az. Early Aug. The outside temps were around 115 degrees. With the gen running the roof A/C. Our 78- 403 Royale's GVW is just under 12,000 lbs. Plus we where pulling a trailer with a car on it. Total GVW was at just over 17,000 lbs. We have no extra venting above the front wheels. Pure stock exhaust that includes gas tank heatshields between the tail pipe, and both gas tanks. I had made, and installed new heatshields that were longer, and taller then the stock ones. Then attached them to the floor above. Used the stock engine fuel pump with a boost pump at the rear for the carb.
> I now have 2 pumps at the rear. That are mounted on the outside of the frame. Along with the 2 filters, relay, and steel line to just behind the left front tire. This feeds a Howell/GM EFI.
> 2 years ago I installer 2 Magna flow series 40 muffler copies. The Magna Flows are about $78 each. The copies are $33. on Amazon. There're about 8 inches shorter then stock.( Thus less heat transfer to the bottom of the GMC. ) With a big plus of being made of a heavy welded steel construction. It's all in the details. Bob Dunahugh 78 Royale Iowa
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| Re: [GMCnet] Mufflers? [message #341957 is a reply to message #341948] |
Sun, 24 March 2019 19:42 |
amansfield1104
Messages: 80
Registered: August 2009
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Thanks Bob. I’ll try the mufflers. Yes raping will shorten the life. I like the idea of doing extra installation between the tanks and the 3 inch pipe.
Art
76 26' Eleganza
> On Mar 24, 2019, at 12:27 PM, Bob Dunahugh via Gmclist wrote:
>
> Headers radiate a huge amount of heat under the entire coach. Verses the stock manifolds. It's all in the surface area of each. Muffler size also plays into this heat transfer issue. Wrapping any exhaust components will greatly reduce their service life. In 2008 we were in Lake Havasu City Az. Early Aug. The outside temps were around 115 degrees. With the gen running the roof A/C. Our 78- 403 Royale's GVW is just under 12,000 lbs. Plus we where pulling a trailer with a car on it. Total GVW was at just over 17,000 lbs. We have no extra venting above the front wheels. Pure stock exhaust that includes gas tank heatshields between the tail pipe, and both gas tanks. I had made, and installed new heatshields that were longer, and taller then the stock ones. Then attached them to the floor above. Used the stock engine fuel pump with a boost pump at the rear for the carb.
> I now have 2 pumps at the rear. That are mounted on the outside of the frame. Along with the 2 filters, relay, and steel line to just behind the left front tire. This feeds a Howell/GM EFI.
> 2 years ago I installer 2 Magna flow series 40 muffler copies. The Magna Flows are about $78 each. The copies are $33. on Amazon. There're about 8 inches shorter then stock.( Thus less heat transfer to the bottom of the GMC. ) With a big plus of being made of a heavy welded steel construction. It's all in the details. Bob Dunahugh 78 Royale Iowa
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| Re: [GMCnet] Mufflers? [message #341965 is a reply to message #341957] |
Mon, 25 March 2019 06:48 |
jimk
Messages: 6734
Registered: July 2006
Location: Belmont, CA
Karma: 9
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Bob,
Your part correct about radiation of heat.
These headers we sell are the Tri-Y design, two combinto one at the
beginning so lesser pipe than the Racing headers.
All are coated inside and outside with High Temp Ceramic that contain the
heat rather Efficiently.
There are other things one can address to overcome the issue.
On Sun, Mar 24, 2019 at 8:43 PM amansfield1104--- via Gmclist <
gmclist@list.gmcnet.org> wrote:
> Thanks Bob. I’ll try the mufflers. Yes raping will shorten the life. I
> like the idea of doing extra installation between the tanks and the 3 inch
> pipe.
>
> Art
> 76 26' Eleganza
>> On Mar 24, 2019, at 12:27 PM, Bob Dunahugh via Gmclist gmclist@list.gmcnet.org> wrote:
>>
>> Headers radiate a huge amount of heat under the entire coach. Verses the
> stock manifolds. It's all in the surface area of each. Muffler size also
> plays into this heat transfer issue. Wrapping any exhaust components will
> greatly reduce their service life. In 2008 we were in Lake Havasu City Az.
> Early Aug. The outside temps were around 115 degrees. With the gen running
> the roof A/C. Our 78- 403 Royale's GVW is just under 12,000 lbs. Plus we
> where pulling a trailer with a car on it. Total GVW was at just over 17,000
> lbs. We have no extra venting above the front wheels. Pure stock exhaust
> that includes gas tank heatshields between the tail pipe, and both gas
> tanks. I had made, and installed new heatshields that were longer, and
> taller then the stock ones. Then attached them to the floor above. Used the
> stock engine fuel pump with a boost pump at the rear for the carb.
>> I now have 2 pumps at the rear. That are mounted on the outside of
> the frame. Along with the 2 filters, relay, and steel line to just behind
> the left front tire. This feeds a Howell/GM EFI.
>> 2 years ago I installer 2 Magna flow series 40 muffler copies. The Magna
> Flows are about $78 each. The copies are $33. on Amazon. There're about 8
> inches shorter then stock.( Thus less heat transfer to the bottom of the
> GMC. ) With a big plus of being made of a heavy welded steel construction.
> It's all in the details. Bob Dunahugh 78 Royale Iowa
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
>
> _______________________________________________
> GMCnet mailing list
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> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
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--
Jim Kanomata
Applied/GMC, Newark,CA
jimk@appliedairfilters.com
http://www.appliedgmc.com
1-800-752-7502
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Jim Kanomata
Applied/GMC
jimk@appliedairfilters.com
www.appliedgmc.com
1-800-752-7502
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