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Old 06-30-2015, 07:04 AM   #1
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1978 28' Argosy 28
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Dual to single exhaust anyone?

My 28' Argosy (454/th400) is headed to the muffler shop next week for a complete new exhaust from the manifolds back. Its currently running dual (2.25"?) all the way back with no crossover. I"m assuming its factory. I'm not a big fan of Chevy dual exhaust. I much prefer the unified sound of a single exhaust dump over the pulsing singles. I'm sure I could instruct the installer to do this but would like the feedback of anyone who's done it. OR decided not to. Just seems easier to have a single exhaust out the back instead of carrying double the tubing/double the mufflers/double the hangers etc. I'm sure I'd have to go to a larger diameter pipe to achieve proper backpressures etc. Not my area of expertise, but will have to relay on you guys and the knowledge of the installer.

Thoughts?

Ben
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Old 06-30-2015, 08:48 AM   #2
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4 inch pipes with gutted cat backs. Great sound.
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Old 06-30-2015, 09:00 AM   #3
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No need for cats of any kind to the best of my knowledge. I think motorhomes of this vintage were smog exempt back in the day. I have Zero emissions ports on my intake manifold and no cats. And don't plan on changing that.
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Old 06-30-2015, 10:33 AM   #4
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I've always preferred the way duals sound with an H-pipe crossover. It smooths out the sound while still having a classic dual exhaust character to the sound, and at least in theory improves performance. I think the sound is most of the difference.
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Old 06-30-2015, 10:53 AM   #5
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When I had my 310 454 done many years ago (mid 90's) they replaced the stock manifolds with new motorhome designed headers (maybe Thorley, not sure anymore) and then to a single large muffler and exhaust out the drivers side, in front of the wheels. It made a vast improvement in the cooling issues I had, and was pretty musical, that is folks knew when you were starting off. I had a friend who said their dog (who liked me a lot) would get all excited long before they knew I was arriving. They figured he could hear the motorhome far off.

At any rate, it was a good change. I wish I could tell you more about the exact parts but it was 20 years ago I had it done.
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Old 06-30-2015, 11:26 AM   #6
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Ben,

I bought a set of Doug Thorley Tri-Y Headers for my Argosy. Unfortunately I haven't been able to test them yet

I shopped until I found the best price and bought them. I plan on using a single exhaust system with the headers. I really like the heat dissipation that headers provide over cast iron manifolds.

Brad
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Old 06-30-2015, 12:25 PM   #7
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Ben,

I have the Banks Power Pack system on my '82 280 which is a two into one system. It is designed to increase HP and torque at the RPM range that we drive these rigs (much different then what one would do for a race car).

I'm very happy with this system for its performance and sound. You can duplicate the Banks system probably at a much lower cost (maybe not however if you are paying someone labor to fabricate a system). I don't have experience driving my rig with the stock setup since it was my dad who had the Banks system installed.

I believe it was at the time that the second right side stock cast iron exhaust manifold cracked due to heat that my dad went to the Banks system. I do like how the rig gets up and goes and it sure sounds good!

Chevy had also put out a service bulletin for the P30 motorhome showing how to install a sheet metal panel on the right side to aid in directing more air flow over the exhaust manifold. If you don't already have this, I suggest you install one. My dad had also done this years ago.

The type of muffler and the sizing of the pipe are going to determine whether you gain any benefit or not. The largest pipe is not always the best...I would follow what Banks does...they have already done the research and development.

The Banks system exits on the drivers side just in front of the rear wheels. This makes for a better sound for the driver!!! It also "helps" direct exhaust away from the door and your CO detector. Well maybe not really. When my CO detector was located next to the door, it only took about 20 seconds for it to go off with the engine running and the door open. Now with my CO detector located back in the galley it only takes about 90 seconds before it sounds!!!

I think a header is a header for the purpose that we are using them for here. My only suggestion is to purchase headers with a good coating or coat the ones you buy so that they don't turn into a pile of rust in a short amount of time. I would love to take mine off and ceramic coat them, but I don't want to deal with the possibility of breaking off a bolt in the head or breaking off one of the air pump injector fittings. I thought of wrapping the headers at one point, but in doing the research, this is just another one of those "race car" things that does us no good and it also promotes rust since the wrap prevents moisture from escaping.

One issue that you may experience with headers is that they tend to loosen up and leak at the manifold to head surface and at the collector to exhaust pipe flange. If you have the money, go ahead and try those Stage 8 fasteners and let us all know how they work out! If I ever remove my headers to sand and coat them, I'm going to try them out.

Take a look at the Banks system for info on how to do your custom install...

http://assets.bankspower.com/manuals...340-v3-web.pdf

Banks Power | 82-95 GM - 7.4L>>PowerPack® System
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Old 06-30-2015, 12:33 PM   #8
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The Banks system also includes heat shields for the oil filter and the starter, both of which are great ideas!
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Old 06-30-2015, 12:57 PM   #9
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The right side heat shield/air deflector is described in the Chevrolet Motorhome Chassis Service Guide starting on page 7-4.
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Old 06-30-2015, 02:04 PM   #10
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Ditto to everything Dean said

I chose Thorley headers mainly due to the price difference compared to the Banks system. For me it was hard to justify the price difference vs the amount the coach would be used. The reviews on the Thorley headers implied they would be good in the rpm range we run these rigs and the ones I bought are coated as well.

The 1984 310 that we had came with the Banks system when we bought it and Dean's right the sound is great and it's an overall great package. But it ain't cheap

I plan on modeling my Argosy exhaust system to match the Banks system in size and configuration. Will it work as well as the Banks system, probably not quite as well but hopefully will be close enough for me.

Dean, our 310 didn't have the oil filter and starter heat deflectors which tells me they were likely lost in action at some point. Any chance that you could post a picture or two of each?

Brad
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Old 06-30-2015, 02:13 PM   #11
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GREAT info gentlemen. Awesome. Sounds like there's a few votes for a single tube so thats the current plan. Dadstoy, I appreciate the banks link. Looks like they're using a 3" pipe after the merge, so should be easy enough to replicate at the fab shop.
While I Love the idea of both headers and the banks system, I'm following the 'if it ain't broke don't' fix it' routine right now. I have no cracked manifolds and am simply looking to have an exhaust that doesn't leak. Frankly, neither of those options are in the budget right now anyway. My Moho runs fair enough, doesn't overheat and has enough power to make it up most hills respectably. So, no immediate need for power or lower temps. Yes, they're both great upgrades, but I'm going to keep it simple for now. I've got plenty of other things I could spend $$ on right now. Like tighter steering.
I"ll look into that heat deflector. Should be easy to fab something up on the cheap!
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Old 06-30-2015, 02:18 PM   #12
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I don't think I have any pics of the heat shields. I'm not planning on heading to the ranch for about 3 weeks, but when I do, I'll get some pics.
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Old 06-30-2015, 02:19 PM   #13
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I think one of the best things you could do now is to add that right side heat deflector!

Quote:
Originally Posted by bpg_austin View Post
GREAT info gentlemen. Awesome. Sounds like there's a few votes for a single tube so thats the current plan. Dadstoy, I appreciate the banks link. Looks like they're using a 3" pipe after the merge, so should be easy enough to replicate at the fab shop.
While I Love the idea of both headers and the banks system, I'm following the 'if it ain't broke don't' fix it' routine right now. I have no cracked manifolds and am simply looking to have an exhaust that doesn't leak. Frankly, neither of those options are in the budget right now anyway. My Moho runs fair enough, doesn't overheat and has enough power to make it up most hills respectably. So, no immediate need for power or lower temps. Yes, they're both great upgrades, but I'm going to keep it simple for now. I've got plenty of other things I could spend $$ on right now. Like tighter steering.
I"ll look into that heat deflector. Should be easy to fab something up on the cheap!
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Old 06-30-2015, 02:23 PM   #14
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Brad, look at page 9 of the Banks install manual. This will give you a pretty good idea of what the two heat shields look like. I think you could fab them up fairly easily.
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