Mid-year, under-car exhaust question

[Gary B.]

On a 2.5" under-car exhaust system on a mid-year, the front pipes are clamped to the rear pipes just forward of the center cross member. At that coupling location, is the diameter of the front pipe reduced in diameter to fit into the 2.5" OD rear pipe? Or is the rear pipe expanded in diameter to accept a 2.5" OD front pipe? In other words, which of those two pipes (front or rear) does not have a 2.5" OD? I'm guessing the front pipe has a reduced diameter, but I don't have an example to measure.

Thanks,

Gary

[Edward J.]

Re: Mid-year, under-car exhaust question

Gary,starting in 64 the Mid pipe is expanded over the front pipe and in 63 it was to the front pipe was expanded over the mid pipe .The pipes were not reduced only expanded.

[Russ S.]

Re: Mid-year, under-car exhaust question

The rear pipe has an increased diameter to slip over the front pipe.

[Gary B.]

Re: Mid-year, under-car exhaust question

Russ,

For '66, I know the front pipe slips inside the rear pipe. But I assume the pipe clamps are 2.5" clamps, which suggests to me the rear pipes must have an OD of 2.5", which in turn suggests that the ends of the front pipe are reduced.

But you say the rear pipe is increased, presumably greater than 2.5'. Do you know the OD of the opening on the rear pipe?

Gary

[Russ S.]

Re: Mid-year, under-car exhaust question

Russ,

For '66, I know the front pipe slips inside the rear pipe. But I assume the pipe clamps are 2.5" clamps, which suggests to me the rear pipes must have an OD of 2.5", which in turn suggests that the ends of the front pipe are reduced.

But you say the rear pipe is increased, presumably greater than 2.5'. Do you know the OD of the opening on the rear pipe?

Gary

The rear pipe is expanded to 2.700

[Gary B.]

Re: Mid-year, under-car exhaust question

Russ,

Do you know for '63 and '64, was the OD of the pipe that was also 2.70"?

Gary

[Russ S.]

Re: Mid-year, under-car exhaust question

Russ,

Do you know for '63 and '64, was the OD of the pipe that was also 2.70"?

Gary

Gary, I don't know on 63-64.

[Gary B.]

Re: Mid-year, under-car exhaust question

Gary,starting in 64 the Mid pipe is expanded over the front pipe and in 63 it was to the front pipe was expanded over the mid pipe .The pipes were not reduced only expanded.

Edward,

Do you know the OD of the expanded end of the mid pipe for '64?

Gary

[Edward J.]

Re: Mid-year, under-car exhaust question

Gary if you would like a have a 63 CC exhaust on the floor in garage I can measure if you like.

[Gary B.]

Re: Mid-year, under-car exhaust question

Gary if you would like a have a 63 CC exhaust on the floor in garage I can measure if you like.

Yes, please. This morning I saw a CAD drawing for a nominal 2.5" exhaust clamp and the ID spec for the clamp is 2.67", so I suspect the OD of the pipe to be at that spec or maybe a few hundreds smaller.

Gary

[Edward J.]

Re: Mid-year, under-car exhaust question

Gary, I took the measurement and the the front pipe expansion was 2.70 OD. and the mid pipe was 2.5 OD for my 63, I also took a look at the 63 center hanger clamp from center to center 3" inchs so I guess that the clamp for 63 had a little wiggle room. As I suspect the 64 up also had some.

Note the 64 up center hanger is different, The 63 center hanger is a one year only.

[Gary B.]

Re: Mid-year, under-car exhaust question

Gary, I took the measurement and the the front pipe expansion was 2.70 OD. and the mid pipe was 2.5 OD for my 63, I also took a look at the 63 center hanger clamp from center to center 3" inchs so I guess that the clamp for 63 had a little wiggle room. As I suspect the 64 up also had some.

Note the 64 up center hanger is different, The 63 center hanger is a one year only.

Edward,

The CAD drawing for the clamp gives the center to center distance between legs of 2.94". Could your 3" measurement actually be 2.94"?

Gary

[Alan D.]

Re: Mid-year, under-car exhaust question

For clamps also see Correct C2 Exhaust Clamp Vendor

Is the CAD drawing a GM and if so can I get a copy (or post here)

[Gary B.]

Re: Mid-year, under-car exhaust question

For clamps also see Correct C2 Exhaust Clamp Vendor

Is the CAD drawing a GM and if so can I get a copy (or post here)

Alan,

No, I have not seen a GM drawing. It's just something I found on the internet from one of the clamp companies. I have no way of knowing if the old GM specs are the same, but I assume there is some standardization in the clamp industry that has existed for decades.

Gary

[Alan D.]

Re: Mid-year, under-car exhaust question

Thanks Gary, take a look at the above referenced old thread for some good pictures.

Note I use a 2 3/4 clamp which has a center to center measurement of 3.4" These go over the hanger and pipes - can be secured without leaving much of a dent in the pipes, however wrong size.
In that old thread I noted the nut for a production clamp does not appear to be the same as the N11 2 1/2 clamp since it is a nut with a flange & no lock washer, but have not been able to find any GM references to verify. The 2 1/2 GM clamps shown in the other thread certainly do have a different nut & lock washer.

Was able to find the 63 nut ( 102634 ) which is a Grade 286M, 17/64 thick with plain finish - it was discontinued without anything replacing it.

Have attached Some general GM clamps, note the C2's appear to use only the one's on the right.