'66 off-road exhaust system distinction

[Rob A.]

Exactly what makes the off-road exhaust system different than the standard under car system?

[Michael H.]

Re: '66 off-road exhaust system distinction

Rob,

The "off road" exhaust system looked nearly identical to a standard system but there were some changes inside the mufflers. There were less baffles and, if I remember correctly, the remaining baffles had larger holes. Beautiful music came out of those mufflers, especially when coupled with any engine 340 HP and up. Discontinued about fifteen years ago.

[Bill Stephenson]

Re: '66 off-road exhaust system distinction

-------Mike is correct in all respects. As well, I believe that the off-road muffler is a bit smaller in circumfrence. At least, when ever I installed a set there seemed to be more clearance between the muffler and the lower edge of the rear outer fender, just forward of the rear exhaust filler panel........Bill S

[Kevin M.]

Re: '66 off-road exhaust system distinction

The are also 2 1/2", for PG cars standard was 2" at least 67. Did you find some?

Kevin

[Rob A.]

Re: '66 off-road exhaust system distinction

There is a set of what appears to be original, GM off-road secondary pipes and mufflers on Ebay, but I'm sure the bidding will be out of my interest range shortly.

[Kevin M.]

Re: '66 off-road exhaust system distinction

If vettefinderjim is after them you got that right.

Kevin

[Joe L.]

Re: '66 off-road exhaust system distinction

Kevin, Bill, Michael, and Rob------

All N-11 off-road systems used 2-1/2" exhaust pipes (outlet pipes were the same as standard mufflers at 2", though).

The N-11 mufflers were identical to standard mufflers with respect to external dimensions and configuration----17" in overall length and 24" in circumference.

The difference between standard and off-road mufflers internally involved the number of tubular baffles----standard mufflers have 3 baffles and off-road has 2.

[Michael H.]

Re: '66 off-road exhaust system distinction

Bill,

Another absolutely amazing thing about this system is their life expectancy. I installed a new set of "off roads" on my 66 in fall of 1983 and their STILL on the car. Probably have 30,000 miles on the car since then and they still look fair. The pipes were made nearly twice as thick as auto parts pipes.

I do have the heat riser disabled and open though and I know that helps extend the life of the right side.

[Kevin M.]

Re: '66 off-road exhaust system distinction

My left side is factory.

Kevin

[Michael H.]

Re: '66 off-road exhaust system distinction

Kevin,

That's wild. Almost 40 years old and still going. I thought I was doing well at 23 years. Imagine if there was never a heat riser, the right side might also be the original.