Priya

So, I have a set of 2.5" outlet small block exhaust manifolds and have been looking at the vendors for a complete exhaust system. It seems all they have are systems for 2" outlet or a 2" outlet to 2.5" pipes. Do you know of anyone that makes an exhaust system for the 2.5" outlet small block exhaust manifolds(preferably with an "X" or "H" pipe)? I'd like to avoid the cost of a complete custom made exhaust system.

Also, in looking at 70-72 exhaust tips, no one seems to list a size - don't they come in 2" and 2.5" sizes for small and big block exhaust systems?

DUB

I believe the last time I needed this type of configuration set-up..I called Allens Stainless steel exhaust and they made me what I needed.

And as for exhaust tips..that is where you either become inventive and modify a set on your own...or get them to cut up a set that you supply to them so they can TIG on a new pipe so it can be attached to the end of your exhaust pipe or muffler.

DUB

BLUE1972

The 72 exhaust tips were the same for big block and small block, the muffler dropped the pipe size for the tips on the LT1 and big block.

Every once in a while there are 2.5" tips in SS advertised on E bay - don't know the quality ..

As a thought - you may be able to slide the tips into a 2.5" muffler using a thin shim to make up any pipe difference - chamfering the tip pipe should reduce any flow hindrance as the exhaust gas will be cooler exiting the muffler, less volume and it's a short pipe for the tip.

I've been thinking of doing the same thing on my 350 cu in - 71, going to 2.5" exhaust. Will probably use big block mufflers and center pipe.

Priya

Thanks Dub. I emailed Allen's stainless exhaust and will see what they have to say.

Thanks Blue1972. I checked ebay and Flowmaster sells a stainless exhaust tip with rolled edge and 2.5" inlet but its twice the price of the Corvette vendors. It's inlet is in the centre of the tip (like the 73?) so I assume one needs to use 73 mufflers with 2.5 inch outlet.

Revi

I don't know if it would align correctly, but wouldn't the front pipes from a 65(?) small block (which used the 2.5" exhaust manifolds) work?

0Willcox Corvette

I'm sure I can get you this system and get you some discount on it as well. Give Tommy a call at 812-288-7103 or 800-588-3883. I'll forward him a copy of this message so he'll have a heads up. I'd have to call and find out about a H pipe set up if that's what you want.

And one other thing, you'll have to make sure you have a 2.5" bracket at the tranny... if you don't you'll need one of them too.

Willcox

Priya

Given that the frames are basically the same I think that might work.

Priya

I would like an H pipe and quiet mufflers. I can weld the H pipe in myself if its easier to ship that way. I forgot to mention this is a 79 I've put a 70-73 rear on (if that makes a difference). I'm also talking about a true dual exhaust system, not the Y pipe the stock 79 had. As I recall all the brackets at the tranny were bolt on?

GUSTO14

They will work with a 4-speed, but not with an automatic. As DUB mentioned however Allen's will bend you a set of (full) 2 1/2" pipes in Aluminized or Stainless steel. The 2 1/2" systems were available on some of the early C3's but they were necked down to 2", about 6" from the manifold outlets. Some of the vendors still carry them, including Allen's.

I bought a set of their 2 1/2" pipes (in SS) many years ago for my '73 4-speed and they included the tips with the set. Fit and finish were terrific and they still look terrific today. Ask them about the correct tips for your system when they contact you.

Good luck... GUSTO

Priya

I have the 4 speed. I think I misinterpreted Willcox's post when he mentioned to make sure I have a 2.5" bracket at the trans. I think he was referring to the holes in the transmission crossmember the exhaust passes through needing to be 2.5". If I remember correctly there wasn't a whole lot of clearance between those holes and the 2" exhaust that was on there. Unfortunately I don't have access to the car until spring so I can't measure. Perhaps what I need is the system you describe, one that starts at 2.5" at the exhaust manifolds but necks down to 2" about 6" farther down from the manifolds?

I've heard the wider exhaust pipes are louder than the narrower ones and I want a quiet exhaust. Would a system that starts at 2.5" and then necks down to 2" negate the performance advantage of having the 2.5" outlet exhaust manifolds?

Priya

I just got an email from Allen's - he says they do not ship to locations outside the United States for some reason. He sounded pretty promising up until then.

Alan 71

Hi P,
I believe you'll find that:
There was just one crossmember used for both 2" and 2 1/2" exhaust.
There was just one exhaust hanger bracket used at the transmission mount for both 2" and 2 1/2" exhaust.
Regards,
Alan

Priya

Thanks Alan.

GUSTO14

Actually the pipes I was referring to start at the 2" manifolds with a 2" pipe that 'grows' to 2 1/2" (~6" below) and goes all the way to the rear of the car where it enters the muffler as a 2 1/2" pipe. The 2 1/2" pipes are close going through the cross member, but they do fit with adequate clearance.

The cross member (P below) from 1968-1979 remained the same with the dual holes through it.



Good luck... GUSTO

Priya

Thanks GUSTO14, knowing that eases my mind a lot that what I'm going to get will fit.

Alan 71

Hi P,
This is an original 2 1/2" exhaust system on a very low mileage ZR-1.
Regards,
Alan

The transition from 2" to 2 1/2" pipe.




Notice how much the pipes are flattened for clearance under the differential and rear spring.



Note pipe is welded directly to muffler inlet flange.

DUB

This is what the center exhaust hanger bracket looks like that is mounted where your transmission mount is located.




And Priya...there is a WAY to get the Allens exhaust to you if you run out of options on getting it made up there by you.

DUB

Priya

Dub, I didn't have any bracket like that near my transmission crossmember when I removed my old exhaust system. If I remember correctly there were no hangers on the exhaust near the transmission crossmember, the first ones were just in front of the differential.

DUB

You are correct becasue your old exhaust system was not a TRUE dual system. The bracket I showed a photo of was not needed....but should nowbe used so your dual pipes are secured.

More than likely if you still had a bracket there on your old factory set-up...it was only a single clamp area to hold the one pipe.

IF you are planning on installing a "H' pipe...or 'X' pipe....I would see if you can have that figured out somewhat...so if Alllens can send you the parts that you will weld in yourself.,..at least that has been figured out.

And...for what this is worth...because I have had to deal with exhaust systems that were so welded up that they could not be removed for service work/repairs. So to try to figure out when you are doing this. so IF you have to take it apart...will it be an ease or a ROYAL pain in the backside.

DUB

Priya

The exhaust system that was on the car when I bought it was not a factory exhaust system, it was a true dual exhaust without catalytic convertors. I'll think about how to remove the exhaust system before I weld in any "H" pipe.