1957-1960 Off-Road Exhaust? Real or Not?

[Justin B.]

So many high-power optioned straight axle cars are seen with the "high performance off-road exhaust system." I don't quite understand why! There is no trace of evidence of this option being available until 1962. As a matter of fact, I recently purchased an original Corvette-only-options dealer brochure. There is nothing listed about optional exhaust.
On page 222-223 in Noland Adams book, you can see two factory underneath chassis photos of high performance cars with the cross-over exhaust but with oval mufflers unlike the high performance round versions. So, why is the later-optioned high performance off road exhaust considered normal equipment on the pre-1962 cars? Thanks for your help, JB

[Donald H.]

Re: 1957-1960 Off-Road Exhaust? Real or Not?

Justin,

I have a 245HP dual quad 60. According to the TIM & JG mine should have no crossover and oval mufflers. By mistake I ended up with HP system from Corvette Central. I sold the round mufflers and bought ovals, but I went ahead and installed the crossover header pipes. I haven't had my car judged yet, but the total originality points for "mufflers, tailpipes and hangers" is 20 so I'm sort of guessing I'll take a 5 point hit.

I had seen the picture you reference on 222-223. How do you know the pictures are of HP cars? Because of the crossover pipe? I was sort of trying to justify in my own mine that they could be 245HP cars

Don.

[Bob K.]

Re: 1957-1960 Off-Road Exhaust? Real or Not?

Justin, I have a 56, and was told that the round mufflers were standard, and were changed to the ovals in 61 or 62. The round then became the off road exhaust . This was because the stock round mufflers were pretty loud. My 240 hp with the original mufflers and a 411 gear at 80 mph sounds like a Harley.That also would account for the lack of a part #. Bob K

[Justin B.]

Re: 1957-1960 Off-Road Exhaust? Real or Not?

Don, The pictures in Nolands book (with the crossover pipes) would be for 270 and 290 h.p. cars. Yes, I was referring to the cross-over pipes with the oval mufflers.

[Justin B.]

Re: 1957-1960 Off-Road Exhaust? Real or Not?

I heard the same story as you except that the oval mufflers started in 58'. The factory made photos in Noland's book are of a 58' and a 60'.

[Jim L.]

Re: 1957-1960 Off-Road Exhaust? Real or Not?

So many high-power optioned straight axle cars are seen with the "high performance off-road exhaust system." I don't quite understand why!

Speaking just for myself, the off road exhaust is on my FI '60 because it just sounds so good.

My car has the front cross over pipe and some original GM mufflers (been on the car almost 34 years). In full song, the sound is absolutely musical.

Jim

[Joe M.]

Re: 1957-1960 Off-Road Exhaust? Real or Not?

The GM Parts & Accessory book lists crossover pipes for 57-61 Vettes with FI, and dual 4BC w/H.L. Cam. Low noise mufflers (28.5" long) are listed for 55-61 cars excluding H.L. cam cars. H.L. cam mufflers (26" long) are listed for 1958 - 1961 cars (my parts book CD-ROM stops in 1961).

[Justin B.]

Re: 1957-1960 Off-Road Exhaust? Real or Not?

So, since there seems to be no true explanation or facts out there, would the oval mufflers with the cross-over pipe be a judging deduction?

[Joe M.]

Re: 1957-1960 Off-Road Exhaust? Real or Not?

Judging Guide states that 290 and 270 engines were specified as using exhaust crossover pipes (confirmed in the GM P&A book). Since those engines had the high lift cams, they would have come equipped with round mufflers, not the low noise ovals. If your engine doesn't have a H.L. cam, I don't think it would have been built with a crossover pipe. Having said that, I believe it would be a deduct.

[Bill M.]

Re: 1957-1960 Off-Road Exhaust? Real or Not?

On page 222-223 in Noland Adams book, you can see two factory underneath chassis photos of high performance cars with the cross-over exhaust but with oval mufflers unlike the high performance round versions. So, why is the later-optioned high performance off road exhaust considered normal equipment on the pre-1962 cars? Thanks for your help, JB

'63 parts book: All '57-'61 FI cars and all '58-'61 solid lifter dual 4bbl cars got the crossover
Corvette News: All '57 and all '58-'61 solid lifter cars got round mufflers.
So, Noland's pictures could be of '58 and '60 FI cars (crossover) with hydraulic cam (oval mufflers).

[Bruce B.]

Re: 1957-1960 Off-Road Exhaust? Real or Not?

My recently purchased 57 Corvette Gasser was originally a 283 283 HP 4 speed for which I have ALL the original parts including the engine and exhaust system. It has the crossover pipe (now "pinched" closed) in the exhaust pipes and round off road mufflers.

I have the round mufflers on my 62 and my other 57 because they sound good.

[Justin B.]

Re: 1957-1960 Off-Road Exhaust? Real or Not?

Joe, what is your opinion on the factory photos of the 58 and 60 cars in Noland's book? Also, why is there not an option specifically for the off-road mufflers on 58-61 models but 62? Does your book say that this is a definite "must have?"

[Troy P.]

Re: 1957-1960 Off-Road Exhaust? Real or Not?

All 55s had round mufflers. I believe that is also true of all 56 and 57 cars but I ain't sure about that. But I suspect that they could easily be found in modern times with oval mufflers as when they needed to be replaced most likely the local muffler shop was engaged rather than going to the Chevy dealer and buying OEM mufflers.

[Bill M.]

Re: 1957-1960 Off-Road Exhaust? Real or Not?

All 55s had round mufflers. I believe that is also true of all 56 and 57 cars but I ain't sure about that. But I suspect that they could easily be found in modern times with oval mufflers as when they needed to be replaced most likely the local muffler shop was engaged rather than going to the Chevy dealer and buying OEM mufflers.

FYI: Corvette News Vol 3 no 4 notes that the round mufflers weren't listed in the parts book.

I replaced my '59 OE round mufflers (283/290) with glass packs (about 1964).
I was surprised that the OE round mufflers weren't glass packs when they rusted out and had to be replaced. They had metal baffles.

[William F.]

Re: 1957-1960 Off-Road Exhaust? Real or Not?

Why did you "pinch off" the crossover pipe??