ragtop71

hoping some one can help me with exhaust questions? I have a 1971 olds convertable cutlass Supreme and need whole new exhaust system. the car originally had a single exhaust on a 350 rocket with a 4 barrel. along the line the original owner had dual exhaust installed in a real hack way.The exhaust starts out with 2 into one then they fabricated it by cutting into the line further back welding 2 pipes and bending funky to make 2 pipes out of the rear making this not a true dual exhaust I like to call it the 71 fake out. I know would like to make this a true dual exhaust and could use some suggestions like question " what exhaust manifolds and system should I use to make this a true tight sounding dual exhaust I am not into a loud thunder crack I prefer the sleeper mode and my one mechanic told me to ask if the left side manifold needed to be changed out to except its own pipe he knows the right side does not have to does anybody now what the hell he is talking about? all I know is I want it to be true blue duel exhaust with a nice pur to it any suggestions?? need to have done b-4 drive time which is now thanks any help is more than appreciated

Rickman48

Most any decent exhaust shop should be able to create "true duals" from your exhisting manifolds.
The mufflers you're describing were called 'hemi' mufflers, back in the day, but you want a high-flow, low restriction muffler, they might have to order.
Expect to pay around $300 at todays prices.

69442C

The exhaust manifolds were different between a single exhaust system and duals. The main differences are the angle of the outlet on the driver's side goes more downward and the passenger side has 2 ports. The driver's side outlet connects to the passenger side via a cross over pipe that runs under the engine. Many people will cap the port on the passenger side that accepts this pipe from the driver's side. And a good exhaust shop should be able to do that and fabricate a dual system that will connect to the outlet ports on the manifolds. However, if you are looking to buy a dual system "off the shelf", you likely need to change that driver's side manifold and possibly the passenger side too.

ragtop71

thanks for the info Rickman48 you have been more than helpful much appreciated!!

ragtop71

thank you 69442C thats the way it is done at present except they capped the cross over on the passenger side, but thanks you have answered my main question on fabrication that I would have to change manifolds and we know that just about doubles the expense if not more due to old manifold bolts out may end up having to pull motor this way I thought maybe they sold kits that would bolt up to original manifolds I will do some searching like on opgi maybe they do in any case thanks for sending me in the right direction the stupidest question is the one un asked that is why I ask before I do these days it's easier thanks again

GTI_Guru

For what it's worth...

I have seen plenty of exhaust manifolds for sale on Ebay at reasonable prices here lately. Just checked, and there's not too many at the moment, but there are usually plenty available, including the single manifold for converting to dual exhaust as long as you cap the extra port on the passenger side.

Keep your eyes out on there for the one you need. They'll be available, and probably not too expensive for a used set or just the single reproduction left side, which is the one you really need to do it correctly.

The only thing I don't know about for sure is if the 400/425/455 exhaust manifold will bolt up to your 350. I know the deck height isn't the same on that engine, but the manifolds may share the same bolt pattern. Someone else will probably chime in to fill in the gap on that tidbit since I'm not positive.

Also, if those won't work, look for one off any of the 260/350/403 engines, as those should be a direct match for sure. Junkyards should have some available, and a decent machine shop can even drill & tap the flange bolts when they break off during removal. I've done that repair myself a few times in the garage, but a drill press makes it a LOT easier.

Also, make sure you're getting manifold(s) for a RWD car. The toronado manifolds will not work properly. They are quite a bit different angle for the outlet, and you'd probably have to "adjust" the firewall to make those work.

Too bad you're not closer. There's a REALLY good exhaust shop here near me that does great custom work for very reasonable prices, and I've always been extremely happy with his work and prices. I can't even buy pre-bent pipes for what he charges for his own custom bent exhausts installed and ready to rumble!

-Jeff

jag1886

I installed a set of Thornton exhaust manifolds when I did my system they are set up for a "true dual" system, they are based on the larger 455 manifolds and have the 350 dumps added to them. They have a 2.5" exit on the PS and a 2.25 exit on the DR side, they totally eliminate the Mix-Master way the Olds does it on the PS. They fit perfect and are built larger inside, someone here tried to tell me they are exactly the same manifold as the small block ones but I had them laying side by side and they do have a larger internal volume. They are pricey but well worth it if you don't want to listen to header pinging. From there any good shop can build what ever you want.

bccan

No difference in small block manifolds, regardless of engine/exhaust for Cutlass in a 71, or 68-72, maybe goes further than that. Dual exhaust simply caps off the x-over flange on the right side & runs a pipe off rear flange of both manifolds.

Simply buy or have a system made & install it. If it were me, I would buy a 2.5" system from TorqueTech or Pypes w/ an "X" pipe and system will fulfill your needs even if you were to upgrade(?) to headers later & simply reconfigure the front of the system. I have seen where others have used Summit or Jeg's system & been happy. I have used many different approaches - very simple "stock" system that you can buy from Napa or any other parts store, Olds specialty suppliers, etc. You can have a shop make you a system in either stock config or a larger pipe size with or without a crossover/connector pipe between the two sides. Torque Tech is good but last I knew didn't have stainless. My preference is Pypes due to stainless & reasonable price IMO. I did have trouble w/ Pypes tail pipes not being bent correctly for a cutout bumper exit but a torch, a plan & some muscle resulted in a good fit.

Some folks don't like the X pipe sound (I do) & if that is the case or you think it might be an issue, use a system w/ simple connector pipe. Popular muffler is Walker Dynomax Hemi Muffler (long case). Cheap, nice sound without a lot of noise or droning, buzzing, rapping noises.

If you use a 2.5" system you will need to make a "bushing" for the pipe connection to the left side manifold. Pipe is 2.5", manifold is 2.25". This is very simply done by using a very short flanged piece if 2.25" pipe placed between the 2.5" pipe & manifold to "adapt the sizes & have a leak free connection.

64Rocket

There is no need to change manifolds. A quality muffler shop knows exactly what to do. If you want you can buy one of those kits that has all the parts and let the muffler shop handle the job. A good muffler shop can make the whole sys by bending there own pipes. Or again buy the kit and let them do it.
Will save you a lot of headaches.

Gene

ragtop71

Thanks to everyone for your input i am more than grateful and believe i am armed with enough info. To get this done right thanks again!!!

jerseyjoe

Ragtop I just put duals exhaust on my 68. You can get the stock setup online for approx $400 with shipping but it includes the stock style mufflers. I wanted better mufflers so I went the route below.

thepartsplaceinc.com (as well as others) have the block off plate for the passenger crossover pipe opening- (1964 - 1975 Cutlass/442) BLOCK-OFF PLATE -EX2604T

Below is a link for a photo of walker parts. both tailpipes and the right side front pipe are available. I found a local Midas with the bend card to make up the left side front pipe. The muffler hangers are available but the tailpipe hanger is just the rubber portion.
The whole set up will cost (excluding the left side front pipe) around $150 from rock auto. The left side pipe will cost b/t $120 and $150 unless maybe you know someone that can bend it for you.

http://info.rockauto.com/Walker/Deta...2511-11430.jpg

The left side front pipe, muffler and tailpipe are 2 inch. You will need to use the walker connector and reducer(listed below) for the right side as the stock pipe was too short for the super turbo muffler and the tailpipe is 2 inch on the right side as well. You will need at least three 2 1/4" clamps for the right side and two 2 inch clamps for the left side. I would suggest using the heavy duty clamps. I used the super turbo mufflers listed below, they have a nice sound without blasting you out of the car.

WALKER Part # 17732 2 1/4" ID Inlet- Outlet--Dual Offset DYNOMAX SUPER TURBO
WALKER Part # 17736 2" ID Inlet- Outlet--Dual Offset DYNOMAX SUPER TURBO
WALKER Part # 41953 Reducer; Reducer Connector; OD - ID: 2 1/4 to 2 "; Length: 4.5"
WALKER Part # 41956 CONNECTOR; ID - OD: 2 1/4 to 2 1/4"; Length: 12"