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bpg_austin · 06-30-2015, 06:04 AM

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

AWCHIEF · 06-30-2015, 07:48 AM

4 inch pipes with gutted cat backs. Great sound.

bpg_austin · 06-30-2015, 08:00 AM

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.

**DKB_SATX** · 06-30-2015, 09:33 AM

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.

idroba · 06-30-2015, 09:53 AM

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.

bkahler · 06-30-2015, 10:26 AM

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

dadstoy · 06-30-2015, 11:25 AM

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

dadstoy · 06-30-2015, 11:33 AM

The Banks system also includes heat shields for the oil filter and the starter, both of which are great ideas!

dadstoy · 06-30-2015, 11:57 AM

The right side heat shield/air deflector is described in the Chevrolet Motorhome Chassis Service Guide starting on page 7-4.

bkahler · 06-30-2015, 01:04 PM

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

bpg_austin · 06-30-2015, 01:13 PM

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!

dadstoy · 06-30-2015, 01:18 PM

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.

dadstoy · 06-30-2015, 01:19 PM

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

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!

dadstoy · 06-30-2015, 01:23 PM

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.

bkahler · 06-30-2015, 01:35 PM

Quote:

Originally Posted by dadstoy

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.

Dean, I don't have the 310 anymore and all of the manuals went with it, the Thorley headers are for my Argosy. I did buy a heat shield for the starter (sort of funky to install on the starter!) but don't recall seeing anything available for the oil filter guess I need to do some googling

So no need to worry about pictures!

One thing I noticed about the Banks system was how long the collectors were. They were at least a foot or two longer than any other headers that I have seen in the past. Also if I'm not mistaken they are stainless as the ones on the 310 were at least 15 years old and still looked new.

Brad

bkahler · 06-30-2015, 01:39 PM

Quote:

Originally Posted by bpg_austin

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!

One thing about the Banks setup is I really do think it improved the overall power and mpg of the 310. Even pulling a 14' trailer with a race car it did really well in the mountains in Kentucky, Virgina, West Virginia and Maryland. One heck of a lot better than the old 27' Winnebago that we had with the same drive train but stock exhaust system.

But I agree, if it ain't broke don't fix it

lstepp2 · 06-30-2015, 01:53 PM

Dual mufflers with a cross over pipe, (A pipe about halfway down the two pipes. The Crossover allows the engine prevents the to fire correctly and more power.

bpg_austin · 07-01-2015, 06:25 AM

Quote:

Originally Posted by lstepp2

Dual mufflers with a cross over pipe, (A pipe about halfway down the two pipes. The Crossover allows the engine prevents the to fire correctly and more power.

Looks like the banks muffler kills 2 birds with one stone, bringing both single pipes into the muffler inlet before converging to a single pipe. I love it, but doubt I'll be able to duplicate the set-up to that degree. I'll loose the bit of optimization if it means a simple, clean single pipe setup underneath. I'll post up some pictures after its done so we can see what I end up with.
I'll specify what I'd like the shop to do in general, but will leave it up to the tech as to what works and what he can do for my expected price point.

bkahler · 07-01-2015, 06:32 AM

Quote:

Originally Posted by bpg_austin

Looks like the banks muffler kills 2 birds with one stone, bringing both single pipes into the muffler inlet before converging to a single pipe. I love it, but doubt I'll be able to duplicate the set-up to that degree. I'll loose the bit of optimization if it means a simple, clean single pipe setup underneath. I'll post up some pictures after its done so we can see what I end up with.
I'll specify what I'd like the shop to do in general, but will leave it up to the tech as to what works and what he can do for my expected price point.

Sounds like a good plan

One thing about the Banks muffler, it's HUGE! That was one of the things that impressed me about the Banks system, well that and the nice looking headers

martin300662 · 07-01-2015, 06:58 AM

Not wanting to hijack Ben's thread but on a totally related subject; I have just the 'little' small block on our 20ft and there doesn't seem a Banks option for the 350, and there are about 6 different Thorley headers, none listed for a motorhome - is there a kit to increase gas flow out of the 350/P-30 and improve low end power?