I have a 72 Cutlass Supreme with the standard 350 from the factory. I am converting from a single exhaust to dual. Should I go with 2 inch or 2.5 inch pipes for optimum performance? Thanks, Will

 

Do you plan on keeping it pretty stock or hopping it up some? I think 2 1/4 would be fine for it unless you plan on pushing a lot more horsepower.

 

Just staying with the factory motor and after market mufflers for a little better flow (and not a lot more noise). Thanks! Will

 

2 -2 1/4" would be fine.

 

Thanks for the info! I'm planning on doing the same. Is the 2-1/4 stock size of the pipe?

 

I know of a few guys with this combo,I know for a fact that the exhaust manifolds can only hold a 2 and a quarter pipe no bigger. I would also consider cut outs for the track and a h pipe for more torque and the cutouts on a dyno , I saw this are good for 22 flywheel and about 15 at the wheels go for it!

 

I have a 71 CS 350 4bbl and put 2 1/4" exhaust on it with flowmasters. Did not go any bigger since it is a stock low compression motor. It has a really good musclecar sound and a little more power over the single system.

 

The stock pipe was 2 inch.

 

Stock single exhaust sys is 2 1/4 pipe.
Stock dual set up is 2 1/4 on the passenger side and 2 inch on the driver side.
I would go 2 1/4 on both sides. "H" pipe connector will help.
Any GOOD muffler shop can do the job complete.

Gene

 

Hi Gene, do I need to change the headers when going to dual exhaust or will the stock headers will work?

 

When you say headers, are you referring to the stock manifolds or actual headers? You can run duals with the stock exhaust manifolds, the crossover will need to be capped.

 

I would definitely invest in headers. Well worth the added hp and you might as well while you're down there anyway

 

Headers are a personal pereference especially with a stock motor. I had one car with them that I worked pretty good and many without. Ease of maintenance, cost, headaches - stay w stock manifolds and a 2 or 2 1/4 system - H pipe is great idea and go with the old school Dynomax Super Turbo mufflers - very well priced, have been rated for decades best for flow and have a GREAT sound at idle, cruising and when you floor it. I swapped one of these on a single exhaust 71 C/S stock 350 2bbl and the engine revved higher and freer and I could actually feel added acceleration. Gas mileage went up a bit too. WIN WIN WIN!!! Good luck w this!

 

Looks like 2 1/4"pipe diameter and "H" crossover is the verdict. Great, that's what I have with a pair of Flowmaster 40's burbling back there. The final pipe section exits at the bumper. Excellent rumble, minor highway drone and head turning deep.

But the 350's stock manifolds remain. The passenger side has been capped-off but the heat flap thing makes noises until warm. Tried wiring it open with no luck.

There's a company that makes replacement manifolds without the cross-over outlet. These are spendy but nice. I thought of long tube headers or even the shorties, but don't want to go crazy trying to get them to fit. There's a lot of stuff to worm around and I don't want to cut the inner fenders.

http://gawain.membrane.com/~thornton...manifolds.html

 

I just completed the conversion for $140 last weekend on my 72 Cutlass 350/350. That included clamps, a new exhaust crossover cap for the passenger manifold and Pypes down pipes (2 1/2 inch downpipes that already have 2 1/4 manifold connector reducers welded on to the downpipes) with 2 Flowtech Cherry Bombs. U want loud then the glasspacks for under $15 a piece will do it.

I connected the downpipes directly to the cherry bombs and that was it. No hangers needed to hold up a full exhaust system. My neighbors in their mid 60's love it, as it gives them the nostalgia vibe, so they tell me. I don't like the sound (too much of an open header sound) as I ran down to CAP auto yesterday and bought extension pipes to run my turbo mufflers (in the garage since 97) to the rear axle.

 

what did u do to the motor to get 350 hp from a 72