Mid-year, under-car exhaust question

[Gary B.]

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...

Alan,

At least for '66 and '67 the AIM calls for the flanged nut GM #1359887 for the center clamp. That nut is still available from GM.

Gary

[Edward J.]

Re: Mid-year, under-car exhaust question

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

Gary, The clamp I measured quickly with a tape measure so anything is possible. My clamp is a CC clamp that came with the Hanger. I Can tell you that the clamps that Gm made may have not all measured the same leaving some wiggle room, as the era of clamps were likely used through out the GM lines, so pipe and muffler manufacters may of had pipes that varied slightly when expanding.

[Alan D.]

Re: Mid-year, under-car exhaust question

Gary,
That nut is used as the standard factory build for 63 - 102634, 64 - 273802, 65 - ??, 66 - 1359887, 67 - 1359887
Do you have any information (date) when the 1359887 nut started to be used?

I believe that the nut shown in the AIM is for the 2" exhaust while the 2 1/2 exhaust used a clamp with a different nut and lock washer. The small exhaust (2") does show up in 63/64 on low performance engines, "I believe" (do not know for sure)
The larger, N11 - 2 1/2 exhaust, is not listed in the AIM (based upon current understanding).

[Gary B.]

Re: Mid-year, under-car exhaust question

Gary,
That nut is used as the standard factory build for 63 - 102634, 64 - 273802, 65 - ??, 66 - 1359887, 67 - 1359887
Do you have any information (date) when the 1359887 nut started to be used?

I believe that the nut shown in the AIM is for the 2" exhaust while the 2 1/2 exhaust used a clamp with a different nut and lock washer. The small exhaust (2") does show up in 63/64 on low performance engines, "I believe" (do not know for sure)
The larger, N11 - 2 1/2 exhaust, is not listed in the AIM (based upon current understanding).

Alan,

I don't know if the 1359887 flange nut started in '66, or if it started in '65. I don't have the '65 AIM to check. In the '66 AIM on UPC 8, sheet A2, only the flange nut is called out for the center clamp location, and I'm not sure if the exhaust system in the '66 AIM is the 2" or 2.5" system.

I have seen photos of an unrestored '66 and an unrestored '67 with the 2.5" pipes and they both show the flange nuts, without lock washers at the center clamp location. The story differs for the tail pipe extension clamps; they use the standard hex nut and lock washer, not the flange nut.

Gary