Converting from single to dual exhaust

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Old March 19th, 2016, 07:42 PM
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Converting from single to dual exhaust

I've got a 1972 Cutlass with a single exhaust 350 engine. It has the crossover pipe from the driver's side exhaust manifold to the passenger side exhaust manifold. I'm considering going to a dual exhaust with an OEM-like dual exhaust like this one: http://www.ebay.com/itm/350789549979.

A few questions:

1. Any routing/interference issues that I may run into given this car currently has a single exhaust?
2. If a get a muffler shop to hang this (especially if the answers to the above are a bit scary) do I need to scare up a cap for the passenger side crossover exhaust port or should they have these?
3. Any tips from those folks who have done this before?

Thanks -
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Old March 19th, 2016, 07:49 PM
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You can purchase a cap or the muffler shop can make one. Should be no issues with the install. You also might contact a good muffler shop on fabbing a custom exhaust that will look just as nice or better than the one your buying.
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Old March 19th, 2016, 08:00 PM
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Originally Posted by oldcutlass
You can purchase a cap or the muffler shop can make one. Should be no issues with the install. You also might contact a good muffler shop on fabbing a custom exhaust that will look just as nice or better than the one your buying.
Thanks Eric - I'll ask around to see what I can get from some shops.
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Old March 19th, 2016, 08:22 PM
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To give you another option, Scott at Classic Exhaust did a good job on mine, and it arrived all in one box only a few days after I called him.

- Eric
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Old March 19th, 2016, 09:26 PM
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Years ago I had a muffler shop fab the duals on my 72 Cutlass convertible. This really does look to be a good price on this system. As Eric mentioned, most muffler shops can make a system that will look and fit like factory.
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Old March 20th, 2016, 07:57 AM
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The factory simply capped the crossover port on the passenger side manifold, even on the W-31 motors. Nearly every Olds vendor sells a repro of the cap.

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Old March 20th, 2016, 12:48 PM
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I used one of these systems several years ago. It was ok not great. By the time you purchase hangers and clamps and do the work it is just a little more to have a quality system done and you don't do the work. I was just quoted $600 for a complete system installed with either Magnaflow or flowmaster mufflers. When you figure shipping on this system and the extras needed then your time and all. It is worth the $150 -200 more for a built to fit on the car system installed.

Just my input.

Not to mention "the parts place" is not the best place to do business with.
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Old March 20th, 2016, 02:14 PM
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I've got a little different take on this. Unless you are going for an exact factory-style exhaust, why use anything that isn't mandrel bent? This photo is from the ebay ad:



Compare to mandrel bent:



I don't know of many muffler shops who have mandrel benders, either.
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Old March 20th, 2016, 03:42 PM
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For what he's wanting a press bent muffler shop system will suffice. We aren't taking much flow difference that warrants the cost of a mandrel bents system. In addition there may be shops that can provide a mandrel bent system in his area if he so chooses.


I don't like the ebay system because its probably cheap tubing and mufflers.


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Old March 20th, 2016, 04:07 PM
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Originally Posted by lemoldsnut
I used one of these systems several years ago. It was ok not great. By the time you purchase hangers and clamps and do the work it is just a little more to have a quality system done and you don't do the work. I was just quoted $600 for a complete system installed with either Magnaflow or flowmaster mufflers. When you figure shipping on this system and the extras needed then your time and all. It is worth the $150 -200 more for a built to fit on the car system installed.

Just my input.

Not to mention "the parts place" is not the best place to do business with.
Well no shipping since The Parts Place is about an hour away. However reading this and the other replies I'm going to visit a few muffler shops and see what they can do.

Great input folks - thanks!
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Old June 27th, 2016, 11:08 AM
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I was curious as to what kind of luck you've had with this. 1 thing everyone failed to ask was if your transmission cross member was a dual hump or single hump. If it's single you are going to need to swap it out or your exhaust will be sitting pretty low.
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Old June 27th, 2016, 11:20 AM
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Originally Posted by Cutty77
1 thing everyone failed to ask was if your transmission cross member was a dual hump or single hump.
Because we didn't have to. Every single 1964-1972 Cutlass has a double hump crossmember. the single hump crossmembers weren't used until catalytic converters came out in the 1974 model year.
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Old June 27th, 2016, 11:27 AM
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I see. That I did not know.
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Old June 27th, 2016, 11:43 AM
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Originally Posted by dalilama
I'm going to visit a few muffler shops and see what they can do.

Great input folks - thanks!
Unless you need something special I'm a big believer in going to a local guy if you can find one. I went from a cat & a y-pipe & two mufflers to true duals off Thornton manifolds into my existing mufflers & tail pipes on my '79 Trans Am. I found a local guy to bend the head pipes & install for around $275. That included him effing with the tail pipes that were on the car already & from one of these kits that didn't fit right to begin with.
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Old June 27th, 2016, 09:03 PM
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Originally Posted by joe_padavano
Because we didn't have to. Every single 1964-1972 Cutlass has a double hump crossmember. the single hump crossmembers weren't used until catalytic converters came out in the 1974 model year.
My 74's were dubbles.

IIRC, cats came out in 75 for these cars.
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Old June 28th, 2016, 06:16 AM
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Originally Posted by quaddriver
My 74's were dubbles.

IIRC, cats came out in 75 for these cars.
Mine too and it had a points distributor.
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Old June 28th, 2016, 06:40 AM
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As long as you're shopping around, give Scott at Classic Exhaust Inc a call. He's in Geneva, OH. You can buy a whole system or just pipes (I bought my own mufflers) and was very happy with the way they fit my '75 Laguna S-3 when I switched from single to dual exhaust. He bends pipe according to original GM bend cards.
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Old June 28th, 2016, 06:43 AM
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something dawned on me, my 76 and 77 were single hump, BUT the A body member was pretty much universal and I dunno if olds was vertified for export, but the chevies WERE and many many cars went north, south and overseas with non-emission equipment and in some cases, factory duals. Sadly, no one cared and they are likely korean container ship steel right now, but there still might be a population of parts to find.
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Old June 28th, 2016, 06:45 AM
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Originally Posted by crimsoncolby
As long as you're shopping around, give Scott at Classic Exhaust Inc a call. He's in Geneva, OH. You can buy a whole system or just pipes (I bought my own mufflers) and was very happy with the way they fit my '75 Laguna S-3 when I switched from single to dual exhaust. He bends pipe according to original GM bend cards.
<perk!>

does he work in T304 or 409 stainless? my sub crys for a set of factory bends in dual flavor for the big block.
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Old June 28th, 2016, 06:45 AM
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Hi Cutty - I wound up bringing the pipes and muffler to a local shop since I needed a torch to "tweak" the pipe on the driver side to snug up to the manifold and to TIG weld the trumpets onto the exhaust sections. I had neither capability in my garage. They charged me $250 to put it all in. No issues with the cross member at all. They got it to fit very tight. Drones a bit a low speeds compared to the stock single exhaust but cruises with a mellow tone. I may change the mufflers at some point but overall very pleased with the conversion. Also picked up a little HP from what I can tell. Definitely accelerates better





Originally Posted by Cutty77
I was curious as to what kind of luck you've had with this. 1 thing everyone failed to ask was if your transmission cross member was a dual hump or single hump. If it's single you are going to need to swap it out or your exhaust will be sitting pretty low.
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Old June 28th, 2016, 07:02 AM
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Originally Posted by quaddriver

does he work in T304 or 409 stainless? my sub crys for a set of factory bends in dual flavor for the big block.
I know he works with 304 stainless. Not sure about 409. Nice guy...give him a call.
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Old June 28th, 2016, 07:25 AM
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Originally Posted by crimsoncolby
As long as you're shopping around, give Scott at Classic Exhaust Inc a call.
That's what I said on March 19th.

- Eric
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Old June 28th, 2016, 07:33 AM
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Originally Posted by quaddriver
My 74's were dubbles.

IIRC, cats came out in 75 for these cars.
Cats did come out with the 1975 model year and all crossmembers from then on were single hump. I was not 100% certain if all 73-74 cars got double hump or not, which is why I said 64-72 above. Since the OP's car was a 72, that's as far as I needed to go anyway.
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Old June 28th, 2016, 08:10 AM
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Originally Posted by dalilama
Hi Cutty - I wound up bringing the pipes and muffler to a local shop since I needed a torch to "tweak" the pipe on the driver side to snug up to the manifold and to TIG weld the trumpets onto the exhaust sections. I had neither capability in my garage. They charged me $250 to put it all in. No issues with the cross member at all. They got it to fit very tight. Drones a bit a low speeds compared to the stock single exhaust but cruises with a mellow tone. I may change the mufflers at some point but overall very pleased with the conversion. Also picked up a little HP from what I can tell. Definitely accelerates better


Cool. I know converting to dual made a huge difference on my 77. The rest is stock......for now.
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Old June 28th, 2016, 08:12 AM
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Originally Posted by crimsoncolby
I know he works with 304 stainless. Not sure about 409. Nice guy...give him a call.
I did, no dice :-(
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Old June 28th, 2016, 09:17 AM
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Originally Posted by MDchanic
That's what I said on March 19th.

- Eric
Oops...sorry about that, Eric. Another senior moment, I guess.
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Old June 28th, 2016, 09:35 AM
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It's just that with all of the different suggestions here, there are two separate people who have both had good results with Scott, and who recommend him.

I'd say that makes him worth considering.

- Eric
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Old June 30th, 2016, 11:37 AM
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Originally Posted by dalilama
. Also picked up a little HP from what I can tell. Definitely accelerates better


It's the trumpet tips
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