DC10

Looking to add side exhaust to a C2 convertible. This is NOT a survey on the pros and cons of adding side exhaust. That train has already left the station.

I am looking for advice on the type of side exhaust. The engine is a 327/350hp.

I see several options and need input. I see "GM sound" and "Quiet." I also see the side exhaust in 2" and 2.5".

I would appreciate whatever input you can provide on either of these. Also, any advice on the installation would be helpful as well.

Thanking you in advance!!

DansYellow66

I believe GM sound and Quiet are actually one and the same - just different terms. The GM pipes used a 1-7/8 inch perforated core pipe and that's pretty restrictive which when new (before rusting out), lends a somewhat mellow rumble that is not as loud as many of the aftermarket pipes. Sort of depends on the engine too. With a normal compression, mild hydraulic cam motor they are reasonably mellow. But on a higher compression, aggressive cam motor they will sound louder and bit harsher.

The other end of the spectrum are the aftermarket 2-1/4", 2-1/2", & 3" (there may even be some larger) that trend louder and somewhat harsher as the size increases. I have 2-1/2" on a fairly aggressive BB and they are loud. I know a 3" set of sidepipes is definitely car-alarm sounding and window rattling territory. Within the aftermarket series there are minor variations - direction of chamber pipe louvers, size of louvers, packing material in outer sheath, etc. Again, the type of motor will also vary the sound intensity to some degree.

As a final thought - don't believe all advertisers claims. If they advertise large diameter pipes and inner core with the term "Quiet" I can almost assure you they are lying through their teeth.


Hope this helps

Crunch527

Go look at classic chambered exhaust...I used their 2.5 inch pipes and they were great...I should have used 3 inch...also used Hedman coated side pipe headers from Jegs...all fit nice and no issues...I had a local exhaust shop weld the flanges up and off I went.

I want to say the owner's name is Eric maybe? I called him and chatted with him and he is very helpful and will work with you on how to design your pipes if you decide you want something different than he already offers.

As far as noise goes, I don't think the larger pipes are any louder...they are all loud...

Lotsacubes

You didn’t mention if restriction was an issue which helps with the 2” vs 2.5” inside tube. My decision came down to Classic Chambered (Eric) or Sweet Thunder (now Highflo Performance). Both seem excellent folks. I wanted 2.5”, stainless, and a fixture welded assembly. CC couldn’t do that but many highly recommended CC. I ordered SS, GNM, 2.5”, with 3” outer tube, and full length ceramic fabric. My engine is a .070 over 427. At 6500 rpm it’s putting out on the dyno so I didn’t want to hurt the hp, but it must be tolerable for my wife. Haven’t heard them yet, several weeks out. I stayed with my stock L72 cast iron exhaust but we ported them to clean them up and match the aluminum heads. Probably tomorrow I can tell you if they bolt up. It came down to CC and Sweet Thunder. Mine are the first set of GNM with full length ceramic sound absorption. The insides of my stock side pipes are.... I believe 1 5/8”. Those would have strangled my BB.

MikeM

Chew on this awhile.

http://www.dragzine.com/tech-stories...on-strategies/

Lotsacubes

Interesting. Summary: side pipes suck.

Guess we should all pitch em.

65tripleblack

Yeah, I agree. They robbed my 327 engine of a WHOPPING 8 RWHP @ 6700 RPM vs open headers. Down from 414 RWHP to a piteous 406.

MikeM

I am not so sure.

I put them on my '65 when I got it in 1972. I had the under car exhaust on it. It seemed to speed the car up but maybe it was just the noise difference. In any case, I was never embarrassed by the acceleration of the car compared to any others at a stop light.

I also put the similar factory OEM chambered pipes on my '69 Z 28 way back in the '70's . Seemed like it picked up a little over the cross flow muffler as well. Could have been my imagination though?

If you carefully read the article I linked, there's more to back pressure than just pipe size.

PS. When I bought the Z car, I read all about the "design spec" of the tight clearance of the 30-30 cam instead of the recommended 30-30 the tune up spec showed. So I cranked the valves down to "design" and the car became an immediate dog. Nothing to do with the chambered exhaust. I quickly got back in the driveway and put the valves back where the tune up spec said to put them. Problem solved.

smuggler85

Someone once said Quiet Sidepipes is an oxymoron. The pipes you can live with depends on your, or your wifes, tolerence for pain. I'm on my third set of pipes and can actually have a conversation or listen to the radio but it took some experimentation. My car is 64 L76 Roadster, .040 over, Comp XS274S with C/R Muncie and a 3.70 rear.
1.) Allen's 2 1/2" Aluminized - Very harsh and ear plugs at 60 mph.
2.) Classic Chambered "Vette Packs" - Much better but still rattled my brain at highway speeds.
3.) Sweet Thunder Aluminized "Quite" 1 7/8" core - Not too bad but not what anyone would consider quiet. The final solution for me was intalling a TKO 600 with the Sweet Thunder pipes. Cruising at 1800 RPM vs. 3200 RPM makes the car a pleasure to drive now.

C2 Hot Cam Guy

I love my hedman fenderwell headers into a 4 inch turnout pipe. The purists hate them but my car was not original . I admit i am not crazy enough to customize an original c 2

DC10

Thank you for the input. I forgot to put the engine, but it is a 327/350. I must admit that I do not know what determines the pipe size to use. Is it based on the existing connections, or independent of the existing connections?

Also, for some reason Corvette America had two different part numbers for "GM Sound" and "Ultra Quiet." Are you saying, however, that they sound the same?

Thanks again!

DC10

I must admit that I do not know what determines the size. Is it based on existing connections, or merely a matter of choice independent of existing connections? The engine is a 327/350.

Thank you for your input.

DansYellow66

I think the best thing to do is call Corvette America and try to get them to tell you exactly what each one is and the difference. "Ultra Quiet" and Corvette sidepipes together, are sort of an oxymoron. Makes me suspicious of their advertising.

For you engine I would probably go with a 2-1/4 inch one for a good compromise. If maximum performance were your objective I would say the 2-1/2 inch. If you don't mind a bit of edge off of your full throttle performance then something along the 2 inch would help keep the sound levels down a bit.

I would stay away from stainless steel as it has a reputation for being a bit tinny and harsher sounding. My current, aluminized steel Allen pipes are 20 years old and still don't have any sign of rust.

I've heard good things about Classic Chambers Powerstick chambered pipe sections but I'm not aware of anyone using them to commercially jig up a complete C2 sidepipe set. Maybe someone knows of someone who is doing this.

I have also heard good things about installing a balance pipe between the two sides (H-pipe). An H-pipe usually helps make an exhaust system a bit mellower and less harsh as it balances and blends the exhaust impulses from side to side. It's strictly a custom muffler shop thing and it has to be carefully routed to avoid hurting ground clearance. It doesn't have to be big pipe though - even 1-3/4 to 2" pipe works fine. Probably works especially good if you run your intake manifold with the heat risers blocked off. If you are running them open - probably not as great a difference.

wmf62

a bit of a hijack, but I had a similar experience with the specs for the LT1 cam recommended by a forum expert; drove 5 miles before I turned around and readjusted the clearances. could have been beat by a 10 year on a bicycle....

now, back to sidepipes.. it's been over 50years since I've had a sidepipes car and I don't remember them as being over objectionable. both were 65 coupes and both had 327/300s. one thing I can definitely say, they definitely have a 'cool' factor

Bill

Lotsacubes

DC, I highly recommend you talk directly to the Ryan at Sweet Thunder, Eric at Classic Chambered, or Allen's. They are the manufacturers and can provide direct experience. Eric at CC was very knowledgeable and helpful. Many happy customers of CC. The only reason I didn't go CC was I didn't want to do cut/fit/welding. I agree with Dan above. Based on my research and your engine displacement the experts above will probably recommend 2 1/4" inner tube. They will also tell what you need to mate to your exhaust manifold. You'll find many happy customers spread across the three manufacturers I've mentioned. Enjoy the process.

beekppr

I got a set of stainless chambered ones in 2" off eBay. Can't recall who made them anymore. Anyhow, the chambered ones sound incredible...like music to a car guys ears. My car is only 300 hp so 2" is fine. On yours I'd go with 2 1/2"

Quil

CorvetteMikeB

Try Allen's Corvette at www.allencorvetteexhaustsystems.com they specialize in Stainless Steel Exhaust systems including the muffler for C2 Corvettes. They have both Stainless Steel 304 & 409 from which to choose from.

beekppr

Quil, that sounds great! Thanks for sharing.

Quil