Home » Public Forums » GMCnet » Consensus on single or dual mufflers ??
| Re: [GMCnet] Consensus on single or dual mufflers ?? [message #232043 is a reply to message #231994] |
Mon, 02 December 2013 21:17   |
John Hunt
Messages: 70
Registered: January 2011
Location: Orange County, CA
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Hi Emery,
It's all pure opinion, conjecture, and hearsay. All the bad stuff. I did not speak to the original GM engineers, but was referring to several private conversations from GMC owners, respected mechanics, and previous posts on this list. All info I was using to try to decide which route to go.
I believe the rear vs. front discussion I had was with a GMC owner who observed that vehicles in the '70s had muffs in both places, so begs the question why did engineers choose way up front. Not a terrible thing to take under consideration when choosing such an expensive item, and perhaps the answer is "doesn't matter".
Thanks,
John
'76 Eleganza II
Orange County, CA
| emerystora wrote on Mon, 02 December 2013 16:36 |
On Dec 2, 2013, at 3:17 PM, John Hunt <johnhuntltd@gmail.com> wrote:
>
>
> Hi Steve,
>
> I assume you're talking about single muff rear mount Vs. dual muff front? I am trying to decide now which to go with, and will look forward to responses on both configs.
>
> At first I thought single rear would be the way to go - quieter inside and move a heat source away from the engine compartment, but I recall others responding in the past that GMC engineers could have done this but opted for dual muffs near engine, and moving muffler to rear changes engine performance that might require timing and/or mixture tweak.
>
I have had my rear muffler in for several years now and have not noticed any difference in performance and it certainly did not need any timing or mixture tweak.
Where did you hear that?
I have been on the GMClist since almost the start of it and I have never seen anyone post that the engineers at GM could have put it in the rear but opted for the front. Do you have a reference for that or is that just hearsay?
Of course they could have put it in the rear -- they could have even put the engine in the rear but didn't.
Emery Stora
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1976 Eleganza II,
1969 Lotus Elan Plus 2,
1978 Merlyn Formula Ford,
1981 Lola Sports 2000
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| Re: Consensus on single or dual mufflers ?? [message #232044 is a reply to message #231986] |
Mon, 02 December 2013 21:18 |
Steve
Messages: 506
Registered: September 2013
Location: East Greenville, Pa
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Emery,
Nice pictures. I like the transmission pan with what I assume is a tempeture sending unit in the front? It would be nice to monitor trans temps. Do you have an auxiliary trans cooler?
I am thinking about my first gauge modification and I am thinking Tacometer first. It drives me Crazy not knowing rpm.
1978 GMC Royal
Eastern Pennslyvania
1968 Chevrolet C20 396 Camper Special
1969 Chevrolet C20 Camper Special
1985 Buick Electra Park Avenue
1992 Camaro 25th Anniversary Heretage Edition Black
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| Re: [GMCnet] Consensus on single or dual mufflers ?? [message #232057 is a reply to message #232042] |
Mon, 02 December 2013 23:39 |
 |
ljdavick
Messages: 3548
Registered: March 2007
Location: Fremont, CA
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And you might just put a resonator on the back to quiet it down.
Larry Davick
A Mystery Machine
1976(ish) Palm Beach
Fremont, CA
> On Dec 2, 2013, at 7:15 PM, gene barrow <barrowgene@gmail.com> wrote:
>
>
>
> Steve,
> KISS it. Single front muffler. Cheaper, out of the box, NO HASSLE install, and works just fine.
> No significant improvement by doing anything else- unless you prefer to spend extra money and labor rather than driving and enjoying the coach. JMHO.
>
> --
> Gene Barrow
> Lake Almanor, Ca.
> 1976 Palm Beach
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Larry Davick
A Mystery Machine
1976(ish) Palm Beach
Fremont, Ca
Howell EFI + EBL + Electronic Dizzy
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| Re: Consensus on single or dual mufflers ?? [message #232060 is a reply to message #232044] |
Tue, 03 December 2013 00:29 |
roy1
Messages: 2126
Registered: July 2004
Location: Minden nevada
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| Steve Adams wrote on Mon, 02 December 2013 19:18 |
Emery,
Nice pictures. I like the transmission pan with what I assume is a tempeture sending unit in the front? It would be nice to monitor trans temps. Do you have an auxiliary trans cooler?
I am thinking about my first gauge modification and I am thinking Tacometer first. It drives me Crazy not knowing rpm.
|
Tachometer and accurate water temperature gauge.
Roy Keen
Minden,NV
76 X Glenbrook
[Updated on: Tue, 03 December 2013 00:29] Report message to a moderator |
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| Re: [GMCnet] Consensus on single or dual mufflers ?? [message #232069 is a reply to message #232015] |
Tue, 03 December 2013 06:20 |
Steven Ferguson
Messages: 3447
Registered: May 2006
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David,
That would not be effective on the GMC first, because most still have
unblocked Xovers, and second, because of the Y pipe that joins both exhaust
banks. I've had both. Cast irong headers with 3" header pipes into dual
mufflers, and Thorley headers into a single 3" pipe running to a single
rear mounted muffler. ZERO difference in performance with either setup
(unless you compare it to stock), quiet, and no heating up of the floor in
the pass compartment. Just make sure you use a heat shield between the
muffler and the rear floor and an exhaust pipe that exits on the left side
vice rear. Every rear tailpipe I've seen has been squashed because of the
lack of clearance between the bumper and the ground.
Steve F
On Mon, Dec 2, 2013 at 5:27 PM, David Orders <dao@oarsllc.com> wrote:
>
>
> Ken Burton wrote on Mon, 02 December 2013 15:57
> > One advantage of the single system is you do have the possibility of a
> muffler clogging up and forcing exhaust gas through the intake crossover
> underneath the carb. This happens more often than you would thing. Ask
> Jim K. about it.
>
>
> This could be avoided by installing a tube between the headpipes. This was
> common on old muscle cars. I think it was called a balance tube or
> equalizer. The intent was to equalize backpressure between dual exhaust.
> I'm not sure how practical this would be on a GMC, but it's a thought.
>
> Here's a link to one type:
>
>
> http://www.jegs.com/p/Hedman/Hedman-X-Treme-Exhaust-Equalizers/747903/10002/-1
>
>
> --
> 1976 Royale "Twinkie II", 1978 Palm Beach with front end fire. Lynnwood WA
> - “If you could reason with religious people there would be no
> religious people” - House, MD
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Take care,
Steve
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| Re: [GMCnet] Consensus on single or dual mufflers ?? [message #232070 is a reply to message #232038] |
Tue, 03 December 2013 06:32 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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Frank Watson built the engine - guy who got my PB. Dunno 'bout the heat risers except this manifold may not even have any.. it's a hi rise Edelbrock single plane. Although in Ga, doesn't make a lot of difference... it warms up in a mile or so anyway.
--johnny
From: D C _Mac_ Macdonald <k2gkk@hotmail.com>
To: GMC Mail List <gmclist@temp.gmcnet.org>
Sent: Monday, December 2, 2013 10:00 PM
Subject: Re: [GMCnet] Consensus on single or dual mufflers ??
Did you also have the pennies in the block heat riser tubes, Johnny? Talk about making a motor bark!
Didn't want to run worth a damn without considerable warmup time in an upstate New York winter, though!
Mac in OKC
Money Pit
> Date: Mon, 2 Dec 2013 18:28:46 -0800
> From: jhbridges@ymail.com
> To: gmclist@temp.gmcnet.org
> Subject: Re: [GMCnet] Consensus on single or dual mufflers ??
>
> Next time I haule the new used toad to Tejas - likely this summer to SA, I'll buy ya a beer and let you hear the toad bark. It'll take you back to a flathead with Offenhauser heeads and two Strombergs and straight pipes. Toad's a Ranger 302 with 30" headers, 3 inch collectors and Smittys, and then 2 1/2" pipes out the back. There ain't a baffle anywhere in it. It is a safety measure, if you get it above idle in anybody's campground, they'll throw you out for disturbing people.
>
> --johnny
> '76 23' transmode norris
> Brase;ton, GA
>
>
> ________________________________
> From: Carey Bryan <chbryan@bigfoot.com>
> To: gmclist@temp.gmcnet.org
> Sent: Monday, December 2, 2013 6:06 PM
> Subject: Re: [GMCnet] Consensus on single or dual mufflers ??
>
> Hi,
>
> I read this with interest. You might note that Emery Stora has his dual in-tank fuel pumps,and that he has no problem with vapor lock.
>
> Thinking about things for just a minute, you might recall that Emery also has a rear muffler setup. How much extra heat does that hot exhaust going into two mufflers dissipate into the air going back just in a few feet to the fuel tanks in unmodified coaches?
>
> Could it be better to, if convenient, go to a rear muffler setup to minimize heat gain to the gas tanks? I do think so, but have the Royale rear gray tank problem. I don't know the solution for sure, but I think it best to get that heat back behind the tanks as quickly as possible. I think it probable that it could be possible to mount a muffler sideways at the very back of the Royale, inlet and outlet at the same end.
>
> Has Emery solved his vapor lock problem because of his in-tank fuel pump setup or has he solved it because he has moved two very big heat dissipators behind the tanks?
>
> If it were me, I would investigate losing some weight by going to the rear muffler, along with helping avoid vapor lock problems. Some do say that there is an exhaust "bark" with rear single mufflers. It wouldn't bother Dan Gregg. Someone has already installed a resonator to damp the bark.
>
> Johnny Bridges rather likes the bark.
>
> Carey Bryan
> --
> Carey from Ennis, Texas
> 78 Royale, 500 Cadillac, Rance Baxter EFI.
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Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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| Re: [GMCnet] Consensus on single or dual mufflers ?? [message #232071 is a reply to message #232070] |
Tue, 03 December 2013 06:49 |
k2gkk
Messages: 4452
Registered: November 2009
Karma: -8
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I was talking about a flathead Ford engine, Johnny!
Mac in OKC
Money Pit
Sent from my iPhone
On Dec 3, 2013, at 6:32, "Johnny Bridges" <jhbridges@ymail.com> wrote:
Frank Watson built the engine - guy who got my PB. Dunno 'bout the heat risers except this manifold may not even have any.. it's a hi rise Edelbrock single plane. Although in Ga, doesn't make a lot of difference... it warms up in a mile or so anyway.
--johnny
From: D C _Mac_ Macdonald <k2gkk@hotmail.com>
To: GMC Mail List <gmclist@temp.gmcnet.org>
Sent: Monday, December 2, 2013 10:00 PM
Subject: Re: [GMCnet] Consensus on single or dual mufflers ??
Did you also have the pennies in the block heat riser tubes, Johnny? Talk about making a motor bark!
Didn't want to run worth a damn without considerable warmup time in an upstate New York winter, though!
Mac in OKC
Money Pit
> Date: Mon, 2 Dec 2013 18:28:46 -0800
> From: jhbridges@ymail.com
> To: gmclist@temp.gmcnet.org
> Subject: Re: [GMCnet] Consensus on single or dual mufflers ??
>
> Next time I haule the new used toad to Tejas - likely this summer to SA, I'll buy ya a beer and let you hear the toad bark. It'll take you back to a flathead with Offenhauser heeads and two Strombergs and straight pipes. Toad's a Ranger 302 with 30" headers, 3 inch collectors and Smittys, and then 2 1/2" pipes out the back. There ain't a baffle anywhere in it. It is a safety measure, if you get it above idle in anybody's campground, they'll throw you out for disturbing people.
>
> --johnny
> '76 23' transmode norris
> Brase;ton, GA
>
>
> ________________________________
> From: Carey Bryan <chbryan@bigfoot.com>
> To: gmclist@temp.gmcnet.org
> Sent: Monday, December 2, 2013 6:06 PM
> Subject: Re: [GMCnet] Consensus on single or dual mufflers ??
>
> Hi,
>
> I read this with interest. You might note that Emery Stora has his dual in-tank fuel pumps,and that he has no problem with vapor lock.
>
> Thinking about things for just a minute, you might recall that Emery also has a rear muffler setup. How much extra heat does that hot exhaust going into two mufflers dissipate into the air going back just in a few feet to the fuel tanks in unmodified coaches?
>
> Could it be better to, if convenient, go to a rear muffler setup to minimize heat gain to the gas tanks? I do think so, but have the Royale rear gray tank problem. I don't know the solution for sure, but I think it best to get that heat back behind the tanks as quickly as possible. I think it probable that it could be possible to mount a muffler sideways at the very back of the Royale, inlet and outlet at the same end.
>
> Has Emery solved his vapor lock problem because of his in-tank fuel pump setup or has he solved it because he has moved two very big heat dissipators behind the tanks?
>
> If it were me, I would investigate losing some weight by going to the rear muffler, along with helping avoid vapor lock problems. Some do say that there is an exhaust "bark" with rear single mufflers. It wouldn't bother Dan Gregg. Someone has already installed a resonator to damp the bark.
>
> Johnny Bridges rather likes the bark.
>
> Carey Bryan
> --
> Carey from Ennis, Texas
> 78 Royale, 500 Cadillac, Rance Baxter EFI.
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| Re: [GMCnet] Consensus on single or dual mufflers ?? [message #232073 is a reply to message #232071] |
Tue, 03 December 2013 07:16 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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Senior Member |
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OH. Yeah, pennies or plugs. Been years. Bud had a 39 Businessman's Coupe he strung pretty much all the way out. Great for sneaking into the drive - in movie, the two guys in front hadda pay, and the four or five in the trunk eased out one or two at the time by lifting the seatback. You're oinvincible when you're 16 - 17
--johnny
From: D C _Mac_ Macdonald <k2gkk@hotmail.com>
To: "gmclist@temp.gmcnet.org" <gmclist@temp.gmcnet.org>
Sent: Tuesday, December 3, 2013 7:49 AM
Subject: Re: [GMCnet] Consensus on single or dual mufflers ??
I was talking about a flathead Ford engine, Johnny!
Mac in OKC
Money Pit
Sent from my iPhone
On Dec 3, 2013, at 6:32, "Johnny Bridges" <jhbridges@ymail.com> wrote:
Frank Watson built the engine - guy who got my PB. Dunno 'bout the heat risers except this manifold may not even have any.. it's a hi rise Edelbrock single plane. Although in Ga, doesn't make a lot of difference... it warms up in a mile or so anyway.
--johnny
From: D C _Mac_ Macdonald <k2gkk@hotmail.com>
To: GMC Mail List <gmclist@temp.gmcnet.org>
Sent: Monday, December 2, 2013 10:00 PM
Subject: Re: [GMCnet] Consensus on single or dual mufflers ??
Did you also have the pennies in the block heat riser tubes, Johnny? Talk about making a motor bark!
Didn't want to run worth a damn without considerable warmup time in an upstate New York winter, though!
Mac in OKC
Money Pit
> Date: Mon, 2 Dec 2013 18:28:46 -0800
> From: jhbridges@ymail.com
> To: gmclist@temp.gmcnet.org
> Subject: Re: [GMCnet] Consensus on single or dual mufflers ??
>
> Next time I haule the new used toad to Tejas - likely this summer to SA, I'll buy ya a beer and let you hear the toad bark. It'll take you back to a flathead with Offenhauser heeads and two Strombergs and straight pipes. Toad's a Ranger 302 with 30" headers, 3 inch collectors and Smittys, and then 2 1/2" pipes out the back. There ain't a baffle anywhere in it. It is a safety measure, if you get it above idle in anybody's campground, they'll throw you out for disturbing people.
>
> --johnny
> '76 23' transmode norris
> Brase;ton, GA
>
>
> ________________________________
> From: Carey Bryan <chbryan@bigfoot.com>
> To: gmclist@temp.gmcnet.org
> Sent: Monday, December 2, 2013 6:06 PM
> Subject: Re: [GMCnet] Consensus on single or dual mufflers ??
>
> Hi,
>
> I read this with interest. You might note that Emery Stora has his dual in-tank fuel pumps,and that he has no problem with vapor lock.
>
> Thinking about things for just a minute, you might recall that Emery also has a rear muffler setup. How much extra heat does that hot exhaust going into two mufflers dissipate into the air going back just in a few feet to the fuel tanks in unmodified coaches?
>
> Could it be better to, if convenient, go to a rear muffler setup to minimize heat gain to the gas tanks? I do think so, but have the Royale rear gray tank problem. I don't know the solution for sure, but I think it best to get that heat back behind the tanks as quickly as possible. I think it probable that it could be possible to mount a muffler sideways at the very back of the Royale, inlet and outlet at the same end.
>
> Has Emery solved his vapor lock problem because of his in-tank fuel pump setup or has he solved it because he has moved two very big heat dissipators behind the tanks?
>
> If it were me, I would investigate losing some weight by going to the rear muffler, along with helping avoid vapor lock problems. Some do say that there is an exhaust "bark" with rear single mufflers. It wouldn't bother Dan Gregg. Someone has already installed a resonator to damp the bark.
>
> Johnny Bridges rather likes the bark.
>
> Carey Bryan
> --
> Carey from Ennis, Texas
> 78 Royale, 500 Cadillac, Rance Baxter EFI.
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Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
|
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| Re: [GMCnet] Consensus on single or dual mufflers ?? [message #232074 is a reply to message #232073] |
Tue, 03 December 2013 07:25 |
tphipps
Messages: 3005
Registered: August 2004
Location: Spanish Fort, AL
Karma: 9
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Senior Member |
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Probably a different topic, but both the Ragusa and Rockwell Transmission pans have tapped fittings for temperature gauge. Others have also modified their Trans oil pan with a welded fitting for temp gauge.
Tom, MS II
2012 Phoenix Cruiser model 2552
KA4CSG
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| Re: [GMCnet] Consensus on single or dual mufflers ?? [message #232088 is a reply to message #232073] |
Tue, 03 December 2013 10:48 |
k2gkk
Messages: 4452
Registered: November 2009
Karma: -8
|
Senior Member |
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|
Yeah, we hid a couple of guys in the trunk, too. But then the drive-ins started dollar or two for a whole carload and packing the trunk no longer really seemed worth the effort.
Mac in OKC
Money Pit
Sent from my iPad
> On Dec 3, 2013, at 7:17, "Johnny Bridges" <
> @ymail.com> wrote:
>
> OH. Yeah, pennies or plugs. Been years. Bud had a 39 Businessman's Coupe he strung pretty much all the way out. Great for sneaking into the drive - in movie, the two guys in front hadda pay, and the four or five in the trunk eased out one or two at the time by lifting the seatback. You're oinvincible when you're 16 - 17
>
> --johnny
>
>
> From: D C _Mac_ Macdonald <k2gkk@hotmail.com>
> To: "gmclist@temp.gmcnet.org" <gmclist@temp.gmcnet.org>
> Sent: Tuesday, December 3, 2013 7:49 AM
> Subject: Re: [GMCnet] Consensus on single or dual mufflers ??
>
>
> I was talking about a flathead Ford engine, Johnny!
>
> Mac in OKC
> Money Pit
>
> Sent from my iPhone
>
> On Dec 3, 2013, at 6:32, "Johnny Bridges" <jhbridges@ymail.com> wrote:
>
> Frank Watson built the engine - guy who got my PB. Dunno 'bout the heat risers except this manifold may not even have any.. it's a hi rise Edelbrock single plane. Although in Ga, doesn't make a lot of difference... it warms up in a mile or so anyway.
>
> --johnny
>
>
> From: D C _Mac_ Macdonald <k2gkk@hotmail.com>
> To: GMC Mail List <gmclist@temp.gmcnet.org>
> Sent: Monday, December 2, 2013 10:00 PM
> Subject: Re: [GMCnet] Consensus on single or dual mufflers ??
>
>
> Did you also have the pennies in the block heat riser tubes, Johnny? Talk about making a motor bark!
>
> Didn't want to run worth a damn without considerable warmup time in an upstate New York winter, though!
> Mac in OKC
>
> Money Pit
>
>
>
>
>
>
>> Date: Mon, 2 Dec 2013 18:28:46 -0800
>> From: jhbridges@ymail.com
>> To: gmclist@temp.gmcnet.org
>> Subject: Re: [GMCnet] Consensus on single or dual mufflers ??
>>
>> Next time I haule the new used toad to Tejas - likely this summer to SA, I'll buy ya a beer and let you hear the toad bark. It'll take you back to a flathead with Offenhauser heeads and two Strombergs and straight pipes. Toad's a Ranger 302 with 30" headers, 3 inch collectors and Smittys, and then 2 1/2" pipes out the back. There ain't a baffle anywhere in it. It is a safety measure, if you get it above idle in anybody's campground, they'll throw you out for disturbing people.
>>
>> --johnny
>> '76 23' transmode norris
>> Brase;ton, GA
>>
>>
>> ________________________________
>> From: Carey Bryan <chbryan@bigfoot.com>
>> To: gmclist@temp.gmcnet.org
>> Sent: Monday, December 2, 2013 6:06 PM
>> Subject: Re: [GMCnet] Consensus on single or dual mufflers ??
>>
>> Hi,
>>
>> I read this with interest. You might note that Emery Stora has his dual in-tank fuel pumps,and that he has no problem with vapor lock.
>>
>> Thinking about things for just a minute, you might recall that Emery also has a rear muffler setup. How much extra heat does that hot exhaust going into two mufflers dissipate into the air going back just in a few feet to the fuel tanks in unmodified coaches?
>>
>> Could it be better to, if convenient, go to a rear muffler setup to minimize heat gain to the gas tanks? I do think so, but have the Royale rear gray tank problem. I don't know the solution for sure, but I think it best to get that heat back behind the tanks as quickly as possible. I think it probable that it could be possible to mount a muffler sideways at the very back of the Royale, inlet and outlet at the same end.
>>
>> Has Emery solved his vapor lock problem because of his in-tank fuel pump setup or has he solved it because he has moved two very big heat dissipators behind the tanks?
>>
>> If it were me, I would investigate losing some weight by going to the rear muffler, along with helping avoid vapor lock problems. Some do say that there is an exhaust "bark" with rear single mufflers. It wouldn't bother Dan Gregg. Someone has already installed a resonator to damp the bark.
>>
>> Johnny Bridges rather likes the bark.
>>
>> Carey Bryan
>> --
>> Carey from Ennis, Texas
>> 78 Royale, 500 Cadillac, Rance Baxter EFI.
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
> _______________________________________________
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> Unsubscribe or Change List Options:
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> _______________________________________________
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| Re: Consensus on single or dual mufflers ?? [message #232095 is a reply to message #231990] |
Tue, 03 December 2013 11:32 |
bryant374
Messages: 563
Registered: May 2004
Location: Pleasant Valley, NY 12569
Karma: 1
|
Senior Member |
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>
>
snip....I recall others responding in the past that GMC engineers could have done this but opted for dual muffs near engine,....
>
>
Occasionally we hear the question, "why did GMC design it that way?". Here is the answer to that front vs rear muffler question:
1- The front muffler design already existed for the Toronado,was a proven design and didn't need to be redesigned for the Motorhome.
2- The GMC chassis/body was designed as a "multi purpose vehicle", not just a motorhome (per 1972 literature) and later implemented as the Transmode.
3- To allow for multi uses, rear mufflers would pose restrictinon on the limited usable space available for unknown future multi purpose requirements. Even as a motorhome the tanks, dump tube, etc create a very limited area.
Another question that has been asked, "why did GMC put the fuel fill way up by the drivers window?"
Again, some of the reasons stated above apply.
With a multi purpose vehicle you did not know where the windows, furnace intake/exhaust & refer venting would end up. Also there are 50 state/Federal requirements for distances required from fuel fill to exhausts, ignition sources, etc. It only made sense as well as a legal requirement to locate the fill out of the way.
I had been told by a couple of the original GMC engineers what a time consuming hassle it was to satisfy all the 50 state & Federal requirements.
Bill Bryant
PO 1976~PB (owned 34 years)
1914 Ford (owned 70 years)
1965 Corvette (owned 39 years)
GMC Motorhome History
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| Re: [GMCnet] Consensus on single or dual mufflers ?? [message #232106 is a reply to message #232001] |
Tue, 03 December 2013 13:59 |
Jim Bounds
Messages: 842
Registered: January 2004
Karma: 0
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Senior Member |
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I've had a rear muffler system in one of my coaches for several years, using a carb with an original mechanical pump I still got vapor lock down here in Fla. I will say though that having an electric fuel pump near the tank stops the vapor lock issues as soon as I switch it on. As a "countermeasure" when you need it, an inexpensive electric fuel pump on the front aux. tank wired to the A/B fuel solenoid knocks out any problem I have. Actually in town on hot days, I just leave the electric pump on and I do not have the troubles.
My guess is having the pumps back at the fuel tanks is whats making Emery not have vapor lock issues.
Some never have issues running electric pumps all the time, I bow to them. My feeling is looking at the failure rate of electric motors, I want another way to get fuel from the tanks to the carb. Never hurts to have backups...
Jim Bounds
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________________________________
From: Carey Bryan <chbryan@bigfoot.com>
To: gmclist@temp.gmcnet.org
Sent: Monday, December 2, 2013 6:06 PM
Subject: Re: [GMCnet] Consensus on single or dual mufflers ??
Hi,
I read this with interest. You might note that Emery Stora has his dual in-tank fuel pumps,and that he has no problem with vapor lock.
Thinking about things for just a minute, you might recall that Emery also has a rear muffler setup. How much extra heat does that hot exhaust going into two mufflers dissipate into the air going back just in a few feet to the fuel tanks in unmodified coaches?
Could it be better to, if convenient, go to a rear muffler setup to minimize heat gain to the gas tanks? I do think so, but have the Royale rear gray tank problem. I don't know the solution for sure, but I think it best to get that heat back behind the tanks as quickly as possible. I think it probable that it could be possible to mount a muffler sideways at the very back of the Royale, inlet and outlet at the same end.
Has Emery solved his vapor lock problem because of his in-tank fuel pump setup or has he solved it because he has moved two very big heat dissipators behind the tanks?
If it were me, I would investigate losing some weight by going to the rear muffler, along with helping avoid vapor lock problems. Some do say that there is an exhaust "bark" with rear single mufflers. It wouldn't bother Dan Gregg. Someone has already installed a resonator to damp the bark.
Johnny Bridges rather likes the bark.
Carey Bryan
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Carey from Ennis, Texas
78 Royale, 500 Cadillac, Rance Baxter EFI.
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| Re: Consensus on single or dual mufflers ?? [message #232111 is a reply to message #232095] |
Tue, 03 December 2013 14:59 |
John Hunt
Messages: 70
Registered: January 2011
Location: Orange County, CA
Karma: 0
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Thanks for this excellent, constructive, and informative reply, Bill. This is very helpful.
John
'76 Eleganza II
Orange County, CA
| bryant374 wrote on Tue, 03 December 2013 11:32 |
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snip....I recall others responding in the past that GMC engineers could have done this but opted for dual muffs near engine,....
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Occasionally we hear the question, "why did GMC design it that way?". Here is the answer to that front vs rear muffler question:
1- The front muffler design already existed for the Toronado,was a proven design and didn't need to be redesigned for the Motorhome.
2- The GMC chassis/body was designed as a "multi purpose vehicle", not just a motorhome (per 1972 literature) and later implemented as the Transmode.
3- To allow for multi uses, rear mufflers would pose restrictinon on the limited usable space available for unknown future multi purpose requirements. Even as a motorhome the tanks, dump tube, etc create a very limited area.
Another question that has been asked, "why did GMC put the fuel fill way up by the drivers window?"
Again, some of the reasons stated above apply.
With a multi purpose vehicle you did not know where the windows, furnace intake/exhaust & refer venting would end up. Also there are 50 state/Federal requirements for distances required from fuel fill to exhausts, ignition sources, etc. It only made sense as well as a legal requirement to locate the fill out of the way.
I had been told by a couple of the original GMC engineers what a time consuming hassle it was to satisfy all the 50 state & Federal requirements.
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1976 Eleganza II,
1969 Lotus Elan Plus 2,
1978 Merlyn Formula Ford,
1981 Lola Sports 2000
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| Re: Consensus on single or dual mufflers ?? [message #232130 is a reply to message #231986] |
Tue, 03 December 2013 17:06 |
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SeanKidd
Messages: 747
Registered: June 2012
Location: Northern Neck Virginia
Karma: 4
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Senior Member |
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Bill, you are right about the 50 State compliance...this is the reason almost every new car look the same as the next...
When I was looking for an exhaust for my MINI Cooper S, there was a compilation of you tube videos of each exhaust along with sounds...start up, revving, inside and out, most even include drive by recordings of a exhaust note.
Thank you George for posting your exhaust, sounds nice.
Sean and Stephanie
73 Ex-CanyonLands 26' #317 "Oliver"
Hubler 1-Ton, Quad-Bags, Rear Disc, Reaction Arms, P.Huber TBs, 3.70:1 LSD Honda 6500 inverter gen.
Colonial Travelers
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