"offroad" exhaust

[Keith B.]

why was the N11 called "offroad" exhaust when it could be ordered for a street driven car. or was it not approved for all 50 states?

[Edward D.]

Re: "offroad" exhaust

Keith,
The N11 had fewer baffles in the muffler and was thus not as quiet as the standard exhaust. Fewer baffles means a bit louder. However, it also means less restrictive and thus less back pressure and subsequently better power. So, it was designated as "off road", meaning "intended for use in racing" by GM, although plenty of performance street cars were ordered with it. The N11 reputedly actually flowed better than the side exhaust which was louder still. N11 mufflers were also welded to the rear pipe, not clamped. They sound nice, what a corvette should sound like. I always recommend the N11 to customers who need a new exhaust. Corvette Central makes a nice well fitting version of the N11 in both aluminized (recommended) and plain carbon steel as original.

[Jack M.]

Re: "offroad" exhaust

This comes from an old article I read:

[Duke W.]

Re: "offroad" exhaust

[QUOTE=Edward Dupere (60605);863162]Keith,

N11 mufflers were also welded to the rear pipe, not clamped. They sound nice, what a corvette should sound like. I always recommend the N11 to customers who need a new exhaust.
/[QUOTE]

Both base and N11 systems that were installed at the plant had the rear pipe sections welded to the mufflers. Service base mufflers were only available with nipples that required cutting off the old muffler and clamping the service replacement mufflers to the rear pipe section.

Service N11 was only supplied as at the plant. The mufflers were welded to the rear pipe sections, so you could essentially have a "factory installed" N11 system by merely removing the base rear pipe/muffler assemblies and installing the service replacement N11 assemblies on '64 to '67 models with 2.5" pipes.

The factory N11 assemblies will not fit on '63 models unless you also replace the front pipe section because the center joint where the two sections connected are reverse gender relative to the '64-'67 exhaust system, and in any case, they won't fit on early '63 models with the deep wells under the seats because N11 lacks the "kickout" to clear the deep wells.

The N11 mufflers were not really that loud, especially when compared to a lot of aftermarket mufflers. They give the exhaust note a bit more "authority" at high throttle openings, but are not objectionable to most at idle and cruise.

Duke

[William B.]

Re: "offroad" exhaust

Can the N11 be replaced for the standard exhaust and not be detected during judging, or are there indicators that the car was not factory equipped with N11?

[Danny P.]

Re: "offroad" exhaust

This is my 1967 N11 OFF ROAD exhaust with black out whether it was sprayed or mope on the assembly line is the question ?

[Alan D.]

Re: "offroad" exhaust

William, depends upon the Production Options. For 1964 it was offered on all models so you must check your year's options before replacement.
One would also need the correct exhaust manifolds ect. Danny

[Duke W.]

Re: "offroad" exhaust

Can the N11 be replaced for the standard exhaust and not be detected during judging, or are there indicators that the car was not factory equipped with N11?

I believe the answer is yes, however, keep in mind that N11 was only available with engines that had 2.5" manifolds and pipes, which would exclude the 250 HP engine and 300 HP w/ Powerglide.

Duke

[Danny P.]

Re: "offroad" exhaust

William, depends upon the Production Options. For 1964 it was offered on all models so you must check your year's options before replacement.
One would also need the correct exhaust manifolds ect. Danny

Alan, 427/435 hp would have the 2 1/2 exhaust manifolds and they are correct manifolds.

[Donald O.]

Re: "offroad" exhaust

Alan, 427/435 hp would have the 2 1/2 exhaust manifolds and they are correct manifolds.

Quite true, but most of us have Big Block Delete cars.

[James W.]

[Thomas W.]

Re: "offroad" exhaust

I have a 71 LT-1. Low mileage correct car. I currently have Corvette Central aluminized welded exhaust system with the stock muffler. I am thinking about replacing the rear pipes with the welded N11 off-road mufflers. Looking for any thoughts on the CC N11 muffler vs. magnaflow? I have listened to a couple of video comparisons but would appreciate any member opinions. I am leaning in the direction of the N11. Thank you. Tom

[Joe L.]

Re: "offroad" exhaust

I believe the answer is yes, however, keep in mind that N11 was only available with engines that had 2.5" manifolds and pipes, which would exclude the 250 HP engine and 300 HP w/ Powerglide.

Duke

Duke------


Not necessarily 2-1/2" manifolds. The use of 2-1/2" manifolds for small blocks ended with the 1965 model year. However, for 1966-67 the 2-1/2" exhaust was still used for L-75 with manual transmission and L-79. These applications had a forward exhaust pipe that transitioned from the 2" manifolds to 2-1/2".

[Joe L.]

Re: "offroad" exhaust

Alan, 427/435 hp would have the 2 1/2 exhaust manifolds and they are correct manifolds.

Danny------


ALL big blocks have 2-1/2" outlet manifolds; no exceptions. However, not all big blocks have 2-1/2" exhaust. 1969 was the exception as ALL 1969 big blocks, including L-88 and ZL-1, were factory-equipped with 2" exhaust.

[Danny P.]

Re: "offroad" exhaust

Danny------


ALL big blocks have 2-1/2" outlet manifolds; no exceptions. However, not all big blocks have 2-1/2" exhaust. 1969 was the exception as ALL 1969 big blocks, including L-88 and ZL-1, were factory-equipped with 2" exhaust.

I was only referring to manifold size of 2-1/2 I understand there were smaller exhaust pipes all depending on engine size, but they should adjust 1967 Judging manual 7th edition page 202 States - All Big blocks exhaust systems use 2-1/2 pipes from manifold to the muffler .