C3 Exhaust Suggestions

[Kevin Morris]

My '72 has chambered exhaust, and they are a little too loud for me. At some point in the future...hopefully, not too distant future...I plan to install a complete set of aluminized mufflered exhausts. My car is very original, including the original 2" exhaust manifolds. It has been my intent to make/keep it that way. As I see it, I have two options 1) replacing the chambered system with a "more stock" 2" system (including mufflers with 2" inlets and outlets) would put it back to stock, but what if I do not like the sound of the repro mufflers? I believe I am then stuck with a system that I could not go to a set of turbo (or like high perf. mufflers) because the pipes are 2", and it seems most high perf. mufflers have 2-1/2" inlets. 2) I could install a set of 2-1/2" pipes, with a 2" coupler to the exh manifolds, and a 2" section at the end for the tips, and with a muffler with 2-1/2" inlet and 2" outlet. This would solve problem in #1, but would not be stock, as the pipes would be 2-1/2".

Is there a real performance advantage to having 2-1/2" pipes over 2", if your manifolds and tips are only 2"? Do the judges "doc" you for having 2-1/2" pipes on a car that should have 2"?

Kevin #39927

[Jack H.]

Re: C3 Exhaust Suggestions

Technically, judges will look for factory originality and deduct accordingly. If you have a reproduction exhaust system (regardless of 2-inch vs. 2.5-inch), expect subtle differences from the factory production line parts and associated minor deductions based on the degree of discernable difference.

If you replace the reproduction mufflers in that system with something more aggressive in the form of an aftermarket product, the deductions will simply increase to the extent of the discernable differences.

Jumping exhaust size up/down (2-inch front pipe, 2-inch rear pipe, 2.5-inch muffler, back to 2-inch tail pipe) isn't of much advantage. Expect the system to perform under max flow based on the 'weakest link in the chain'....

The acoustic aspect of various systems IS a matter of personal taste and your 'ear'. This might be an excellent opportunity to raise the question at your local NCRS Chapter meeting, get input(s) from fellow members, and actually have the opportunity to try this/that before you buy based on courtesy test rides with fellow members having similar cars with different exhaust systems....

[Kevin Morris]

Re: C3 Exhaust Suggestions

Excellent suggestions Jack. Hey...wouldn't the system sound better, though, if it were on a "red" Vette?

[Richard D.]

Re: C3 Exhaust Suggestions

Was wondering what the benefits were for the 2 1/2" pipes were if they were offered with the manifolds that were 2"?

I'm pretty sure that the exhaust pipes on my 68 are original (they're pretty old looking, but pretty solid), and they have have that "crimp" where they cross over the rear suspension.

Were these the "off-road" system that was offered back then?

Rich

[Kevin Morris]

Re: C3 Exhaust Suggestions

Richard, I doubt seriously if there was much performance difference in the 2" -vs- 2-1/2". If I am not mistaken, the 2-1/2" began appearing on the small block cars with the LT-1 in '70. These same LT-1 cars, however, still came with a 2" exhaust manifold and 2" exhaust tips. The pipe would be 2" for about 3-4" following the manifold, flare to 2-1/2" for the remainder of the length of the car, then reduce again to 2" so the exhaust tip could fit over it. The base 300 and 350hp cars still had the 2" pipes as stock. I am certain, if your '68 is a small block car, that it originally came with 2" pipes. My reason for possibly considering stepping up to 2-1/2" is, if I do not like the sound of the reproduction "stock" mufflers (which have 2" inlets, therefore requiring 2" pipes all the way back), then I may want to try yet a different muffler...say a turbo, or something. These performance type mufflers, however, seem to only come with 2-1/2" inlets.

Kevin #39927

[Jim T.]

Re: C3 Exhaust Suggestions

Kevin my original owner 68 small block came from the factory with 2 1/2 inch exhaust pipes. The exhaust manifolds have the still operating air injection system and have 2 inch outlets. The front exhaust pipe that connects to the exhaust manifold begins as a 2 inch pipe that expands to 2 1/2 all the way to the mufflers. I have the same 2 1/2 inch system on my original owner 70 that I changed from a 2 to a 2 1/2 inch system. The only extra part was the exhaust bracket change from a 2 inch bracket to the 2 1/2 inch bracket.