Dual Exhaust

[Oldscarnut]

I am looking a few notches ahead while I await the 2711 on backorder. Over the weekend I basically put the last things together besides the intake and carb. What a Chunk! It has to be getting near 700 lbs now! So I have read the threads here and also Classic Olds since the engine is from 1968. I installed the Thornton cast iron exhaust manifolds and since I am not working from a replacing the engine standpoint, but swapping, I have a lot of questions about the exhaust pipes, and nothing I have will work. I do not need CATs, that is first, and my Olds Guru tells me 2.25" inch pipes at the donut to 2" at the other end will give me the sound. What I am trying to find is a source of downpipes, that will work well enough for me to start and break-in the engine before I can get it to a muffler shop for the exhaust fitting. I gave up on a DIY system as I cannot weld or bend or cut, and I want the mellow tone of a W-31. Anyone that can give me a source for downpipes in a G Body will be appreciated. I have some great photos of superior looking exhausts with x pipes all put together nicely to fit an Olds 88 or a Trans-am with a 403, but I can't find a G Body Olds. The Thorntons move the right side from stock. I am down to a couple of big dollar expenses now and I want to have it all in place as soon as I can. Summer Shows are already going! It looks like one down pipe bends 90 degrees nearly while the other has a more shallow path.

 

[Michael Watts]

Have you looked at custom system at your local muffler shop. I had cracked my passenger side exhaust manifold .And couldn`t find a replacement .So I bought a set of Flowtech "shorty" headers .Had my Transmission crossmember modified for true 2:25 dual exhaust using my Flowmaster mufflers and custom tail pipes just behind the rear wheels . In my 1981 El Camino SS

 

[Oldscarnut]

Have you looked at custom system at your local muffler shop. I had cracked my passenger side exhaust manifold .And couldn`t find a replacement .So I bought a set of Flowtech "shorty" headers .Had my Transmission crossmember modified for true 2:25 dual exhaust using my Flowmaster mufflers and custom tail pipes just behind the rear wheels . In my 1981 El Camino SS

I intend to let the muffler shop do the work, but I need to run the engine before since it has not yet been started and full of new parts. I was thinking that with downpipes I can break in the cam and then get it to the muffler shop which btw is 20 miles away

 

[Canon_Mutant]

Most everyone has gone to 2 1/2". Not sure why you're wanting to go 2 1/4 to 2? But here are some 2 1/2s. There are others out there Pypes etc. But all are 2 1/2 that I can find.

Also, are you still ECM equipped? You will need someone to install an O2 sensor in the PS downpipe.

https://www.autoanything.com/exhausts-mufflers/flowmaster-manifold-downpipes

 

[olds307 and 403]

Most everyone has gone to 2 1/2". Not sure why you're wanting to go 2 1/4 to 2? But here are some 2 1/2s. There are others out there Pypes etc. But all are 2 1/2 that I can find.

Also, are you still ECM equipped? You will need someone to install an O2 sensor in the PS downpipe.

https://www.autoanything.com/exhausts-mufflers/flowmaster-manifold-downpipes

I agree, my 260 likes 2.5" exhaust with shorties or barely 2" dual exhaust with manifolds, surprised it made a difference. Those 2.5" Ram Air Restorations down pipes look really nice. With SBO manifolds, even the Thornton manifolds or their shorty SBO headers are aimed at 2.25" head pipes fitting the best, which is why I kind of want to try their BBO shorties on my soon to be 424 SBO with the 2.5" head pipes.

 

[fleming442]

I'd probably cobble something together with parts store bends and (maybe) mufflers to get it to the exhaust shop, then let them handle it. What better excuse to drive on the road with open exhaust? "Officer, I'm taking it to get the exhaust done, I swear!"

 

[DoubleV]

Pypes is the only one I know of that has the 2 downpipes that's a direct fit with your Thornton's.

I had this setup years ago and due to poor Thornton quality the the drivers side manifold is ( was? ) cast with a slight forward curve instead of being straight down like it should. This caused my driver's side pipe to not seal well. Good ol aftermarket junk...

 

[WanaBa442]

Has anyone used these on a Cutlass?
SBO transplant using Thorntons shorty headers with a w/G-force crossmember to the Jegs dual kit is the plan...

Most everyone has gone to 2 1/2". Not sure why you're wanting to go 2 1/4 to 2? But here are some 2 1/2s. There are others out there Pypes etc. But all are 2 1/2 that I can find.

Also, are you still ECM equipped? You will need someone to install an O2 sensor in the PS downpipe.

https://www.autoanything.com/exhausts-mufflers/flowmaster-manifold-downpipes

 

[Oldscarnut]

I'd probably cobble something together with parts store bends and (maybe) mufflers to get it to the exhaust shop, then let them handle it. What better excuse to drive on the road with open exhaust? "Officer, I'm taking it to get the exhaust done, I swear!"

Up here, open exhaust seems to be the Norm. Harley's, Diesels, and tiny little zoom-zoom cars never seem to muffle their engines any more.....or any less!!

 

[Oldscarnut]

Has anyone used these on a Cutlass?
SBO transplant using Thorntons shorty headers with a w/G-force crossmember to the Jegs dual kit is the plan...