DZAUTO

My son has recently bought a 73 with 350/auto/factory air cond.
YES, YES, YES, YES, YES, I KNOW, this is the 53-67 section-------------------are you going to make me go over to the 68-82 section for help?

He wants to build and install a SB400 (he's found a complete 78Kmi 1971 SB400 to build).

So, here goes with the question.
The 66-later SB Vettes have 2in Ram Horns. I THINK, I THINK, I THINK, if we install 2 1/2in manifolds, all that will need to be done to complete the system is to use 63-65 2 1/2in exhaust pipes from the 2 1/2in manifolds back. Is that Correct? Is there a difference in 4sp/auto exhaust pipes?
Is there any differences where the pipes pass through the cross member and are attached to the hangers?
Do we have someone here who has converted 68-later 2in manifolds/pipes to 2 1/2in that can say FOR SURE what will be needed to do this conversion??????? (I've not done it, but it SEEMS like a no brainer)

Paul Drennan

I have had this same question for sometime. I wanted to do this on my 71 SB 4spd car. I even considered changing to 73 mufflers to get the 2.5 outlets and tips. I couldn't find a direct cross reference in my old GM parts catalog, but I did find a RF pipe for 65 396 and 71 or 72 454 that shared a part #, so I assume the frames are the same and I also assume the engines are mounted the same. One area of concern in your case would be that no C2 exhaust ever had to be routed around that 400 TH that is in your car. In all the exhaust charts in my book, 4spd and autos use different front pipes. Hopefully, someone has actually tried this and can answer back. And just to save some of you some typing, I know that the performance difference will be miniscule at best, I just think it would LOOK better than that welded joint between 2 different size pipes that came factory on SHP SB cars.Chip.

DZAUTO

Someone has GOT TO KNOW if the 63-65 2 1/2in front pipes (left and right) can be used to convert a 73 with 2 1/2in manifolds!!!!
SURELY, SURELY, SURELY someone has converted their 68-later SB to 2 1/2in!!!!!
Guys, don't make me go over to the 68-82 section!

GUSTO14

Tom, I bought a 2 1/2" SS system for my '73 4-speed from Allen's back in 1991. It fit like a glove and still looks terrific today.

Since my manifolds are 2", my system starts out as 2", but expands to 2 1/2" about 6" below the manifold outlet. It's similar to how it was done on the '66 with the 2 1/2" system.







The '63 automatic header pipes are different than the 4-speed pipes for clearance around the transmission. But that was a power glide and your son should have a Turbo 400. I would give them a call and I'm sure they either have what he needs or will bend them up.

Good luck... GUSTO

gbvette62

I going to say that 63's won't, but 64-65 might. Because of the under seat "tool boxes" in early 63's, 63 pipes are unique to 63's.

In looking at Corvette Central's website, they show that their small block 2" to 2 1/2" 66-67 and 68-74 systems, all use the same head pipes. I have to think if the 2" to 2 1/2" head pipes fit from 66-74, then the 64-65 full 2 1/2" head pipes should?

The following was taken from Corvette Central's website.

CORVETTE EXHAUST SYSTEM - 327 WITH 2" TO 2 1/2" 4 SPEED OFF ROAD / N11 MUFFLER

Year:1966-1967

Set Includes:
322417 1966-1974 2" to 2-1/2" Front Exhaust Pipe
322104 1964-1967 2 1/2" Off Road Welded Muffler

I've used Jack at East Tennessee Vette in Knoxville, a few times to make up modified Corvette exhaust systems for me. A call to him, or Mike at Allen's Stainless, should get you a definitive answer. If the 64-65 head pipes won't work on the 73, I know that either of them can make you a full 2 1/2" system for the 73.

You can reach Jack at East Tn Vette at 800-921-5502, and Mike at Allen's Stainless at 574-722-7272.

mikem350

Call CC, they have lots of info/systems

wmf62

Tom
I know this is the obvious answer, but a GOOD muffler shop can make up whatever you need... I had a full 2-1/2" system fabbed for my 62 and it fits perfectly; no rattles, no problems...

Bill

Blk63Vette

Hello

Yes it can be done. I had a 1968 327 350 car. I put 1965 2 1/2 ram horn exhaust on the car. I bought a 1965 corvette exhaust kit from Corvette Central No problems worked out real good.

DZAUTO

So far, what I've come up with is that I can use 64-65 2 1/2in head pipes-----------------IF, IF, IF my son's car was a 4sp. But it has an automatic and there is no 2 1/2in head pipe that will go around the auto tranny that I can convert the 73 to 2 1/2in. The only option (as it seems) is to get 73 2 1/2in head pipes, cut off the first few inches which are 2in and have a short length of 2 1/2in welded on so that it will mate to the 2 1/2in manifolds.
I simply wanted to avoid having a weld in the head pipe.

gbvette62

As I said in my previous post, I would talk to either East TN Vettes and/or Allen's, about making 73 pipes that are a full 2 1/2" from the connector. Both of them have done similar things for me in the past.

MelWff

You do realize that many the Corvette vendors sell complete exhaust systems for your 73 with a 2" to 2 1/2" step up?

cardo0

I converted my 2" system to the 2&1/2" BB system on my '74 just bolting on what I bought from Chicago Corvette (which had Corvette Central stickers all over it. But I don't think that's what are asking for and I'm reading you are worried 'bout fit with early manifolds and the auto trans. So I will mention the fit of my 2&1/2 BB exh system kinda sucks and is ugly compared to what a dedicated performance exh shop can do. My system pipes are way to close to my now composite rear spring. Man handling those pipes even when new while on a creeper is discouraging in the least.

My advice is to contact the local performance exhaust shop if only to tweak a replacement system or fab a entire new system. BTW Flowmaster has a entire new SS system with X-pipe and 60 series mufflers and X-pipe for '74 and newer C3's. I guess what I'm saying is that even if you can find a bolt-on system it will more than likely look more amatures than a stock system (but that Flowmaster system is a nice piece).

Good luck.