Replacing exhaust system
November 27th, 2020, 08:23 AM
#1
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Join Date: Apr 2014
Posts: 262
Replacing exhaust system
Have a 67 C/S 330 engine, looking for input on replacing the exhaust system with dual exh. Currently have car on jack stands (no car lift available).
Any suggestions on what brand to go with ?
As always Thanks Brian
Any suggestions on what brand to go with ?
As always Thanks Brian
November 27th, 2020, 01:30 PM
#3
Registered User
Join Date: Aug 2014
Location: Western North Carolina
Posts: 619
There are many options available. It would help to know more about what you're looking for.
Stock replacement for an accurate restoration: Garner is probably your best option. Closest to the original system in materials, bends, clamps, hangers, etc. keep in mind this isn't always the 'best' in terms of durability or performance. Also, these systems are quite expensive compared to aftermarket systems.
Functional and easy: Find a local muffler shop to build a system. In the 'old days' this is all that was available. Everything will be 'off the shelf' and made to fit. Decent representation of the original system in terms of bends and routing. Mild steel everything means you can expect surface corrosion to start before you pay the bill.
Aftermarket: Grab a Summit catalog and decide what you want to pay for. Most of these are mandrel bent which will flow better than the original systems but clamps, hangers, etc. won't match the original look if you're doing a restoration.
Almost all of these systems will come with either an 'H-pipe' or 'X-pipe' as those are very common today. Up to you if you think it's necessary for your application but they're both intended to balance the flow better. In theory, this will improve breathing and, therefore, performance. I have no doubt this is true but for a mild compression, lightly modified street engine, good luck being able to tell the difference with either of these.
Aside from tube diameter, the most important thing you should consider is material. As mentioned, I would avoid mild steel for any application. This is the least expensive and may work for you if you don't care too much for durability or appearance. The next step up in cost is 'aluminized'. This is an aluminum based coating applied to the tube to avoid surface rust and keep the system looking good. I've never been a fan of aluminized systems. All exhaust systems have moisture in the exhaust which condenses on the inside of the system. With no protection on the inside of the tube the system can rust from the inside out. I will say I have never researched whether aluminized manufacturers apply anything to the inside of the tubes but my assumption is that they do not.
The most durable solution is stainless steel. As you might expect, they are the most expensive but should last the life of the vehicle - especially our cars which don't see 'normal' winters like they used to. Not too many aftermarket exhaust companies offer stainless. It gets much harder when cold worked and has a tendency to split so forming it is more difficult than mild steel. There are two primary materials offered; 409 and 304. 304 is an austenitic grade and the 'gold standard' for exhaust and will resist surface corrosion even under the most adverse conditions. I'm not aware of any aftermarket exhaust company offering an 'off the shelf' kit for our cars with 304. If they do, be prepared to pay at least twice what you'd pay for a mild steel version.
409 is a ferritic grade and, as such, can corrode under some conditions. However, cost will be lower than 304 and it will almost certainly last the life of the vehicle. Many production cars these days use 409 for some, or all, of the exhaust systems since it's a good balance of cost and durability. Some aftermarket manufacturers offer stainless exhaust system kits for our cars. All of these that I'm aware of use 409.
OK - back to your original question. I run Flowmaster's 'American Thunder' kit in 409 stainless at 2.5" diameter pipe. I have found this to be a great quality kit that fits well and is easy to install. It has an H-pipe and can be purchased with stainless clamps/hardware, mufflers and everything else you'll need. Sound of the Flowmaster mufflers are an 'acquired taste' so you may want to purchase whatever mufflers you want separately.
Keep in mind almost all of the aftermarket kits are 'collector back'. This makes it easier for the manufacturer. They don't have to worry about exhaust manifold placement, etc. and can make the same kit for almost all '68-'72 GM A-bodies (for example). This means that if you're not running headers, you'll also need aftermarket (or custom) downpipes to connect the manifolds to the kit. Pypes makes very nice 2.5" 409 stainless downpipes which will work with factory manifolds or Thornton's 'shorty' headers. Note this is true for the '68-'72 applications. Your car may be slightly different.
Stock replacement for an accurate restoration: Garner is probably your best option. Closest to the original system in materials, bends, clamps, hangers, etc. keep in mind this isn't always the 'best' in terms of durability or performance. Also, these systems are quite expensive compared to aftermarket systems.
Functional and easy: Find a local muffler shop to build a system. In the 'old days' this is all that was available. Everything will be 'off the shelf' and made to fit. Decent representation of the original system in terms of bends and routing. Mild steel everything means you can expect surface corrosion to start before you pay the bill.
Aftermarket: Grab a Summit catalog and decide what you want to pay for. Most of these are mandrel bent which will flow better than the original systems but clamps, hangers, etc. won't match the original look if you're doing a restoration.
Almost all of these systems will come with either an 'H-pipe' or 'X-pipe' as those are very common today. Up to you if you think it's necessary for your application but they're both intended to balance the flow better. In theory, this will improve breathing and, therefore, performance. I have no doubt this is true but for a mild compression, lightly modified street engine, good luck being able to tell the difference with either of these.
Aside from tube diameter, the most important thing you should consider is material. As mentioned, I would avoid mild steel for any application. This is the least expensive and may work for you if you don't care too much for durability or appearance. The next step up in cost is 'aluminized'. This is an aluminum based coating applied to the tube to avoid surface rust and keep the system looking good. I've never been a fan of aluminized systems. All exhaust systems have moisture in the exhaust which condenses on the inside of the system. With no protection on the inside of the tube the system can rust from the inside out. I will say I have never researched whether aluminized manufacturers apply anything to the inside of the tubes but my assumption is that they do not.
The most durable solution is stainless steel. As you might expect, they are the most expensive but should last the life of the vehicle - especially our cars which don't see 'normal' winters like they used to. Not too many aftermarket exhaust companies offer stainless. It gets much harder when cold worked and has a tendency to split so forming it is more difficult than mild steel. There are two primary materials offered; 409 and 304. 304 is an austenitic grade and the 'gold standard' for exhaust and will resist surface corrosion even under the most adverse conditions. I'm not aware of any aftermarket exhaust company offering an 'off the shelf' kit for our cars with 304. If they do, be prepared to pay at least twice what you'd pay for a mild steel version.
409 is a ferritic grade and, as such, can corrode under some conditions. However, cost will be lower than 304 and it will almost certainly last the life of the vehicle. Many production cars these days use 409 for some, or all, of the exhaust systems since it's a good balance of cost and durability. Some aftermarket manufacturers offer stainless exhaust system kits for our cars. All of these that I'm aware of use 409.
OK - back to your original question. I run Flowmaster's 'American Thunder' kit in 409 stainless at 2.5" diameter pipe. I have found this to be a great quality kit that fits well and is easy to install. It has an H-pipe and can be purchased with stainless clamps/hardware, mufflers and everything else you'll need. Sound of the Flowmaster mufflers are an 'acquired taste' so you may want to purchase whatever mufflers you want separately.
Keep in mind almost all of the aftermarket kits are 'collector back'. This makes it easier for the manufacturer. They don't have to worry about exhaust manifold placement, etc. and can make the same kit for almost all '68-'72 GM A-bodies (for example). This means that if you're not running headers, you'll also need aftermarket (or custom) downpipes to connect the manifolds to the kit. Pypes makes very nice 2.5" 409 stainless downpipes which will work with factory manifolds or Thornton's 'shorty' headers. Note this is true for the '68-'72 applications. Your car may be slightly different.
November 28th, 2020, 11:37 AM
#4
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Thread Starter
Join Date: Apr 2014
Posts: 262
Hey thanks for the reply, I like the idea of the 409 stainless steel/ 2.5" pipes. "The kit that you bought was it easy to install over the rear axle?" I hope to install my own in my garage (minimal floor clearance).
Thanks Brian
Thanks Brian
November 29th, 2020, 08:32 AM
#5
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Join Date: Aug 2014
Location: Western North Carolina
Posts: 619
Yes, the system was very easy to install. I put my car up on jackstands and did it in my garage. My car is a 442 so I used the straight tailpipe sections and everything lined up perfectly with the bumper cut-outs. The tailpipes are 1 piece from the mufflers back and slip over the rear axle easily. Make sure to keep everything somewhat loose and resist the urge to tighten anything until all the pieces are fitted and you have everything where you want it. Have a few blocks or extra jackstands to hold the center section up and in place while you're fitting the mufflers and rear pieces.
December 2nd, 2020, 10:20 AM
#7
Registered User
Join Date: Aug 2014
Location: Western North Carolina
Posts: 619
No, mine's a '69. The '67 routing is essentially the same with minor differences in bends, lengths, etc. so you'll need to source a kit specific to your model year. The install should be identical, including 1 piece rear sections, etc.
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