1970 BB Automatic Exhaust Clamps

[Carr C.]

I have a 1970 454 automatic Corvette.

The JG is kind of nebulas as to which style of exhaust clamp is suppose to join the primary pipes to the intermediate pipes.

From what I've deciphered the 454 automatic clamps are not the usual clamps.

It shows in diagram 6.1 that it should be an enclosed guillotine type clamp but does not pin down if it has the round u-bolt or the flat u-bolt.

I would like to know exactly what would be correct for judging on a '70 454 automatic car.

Thanks in advance!

[Mark E.]

Re: 1970 BB Automatic Exhaust Clamps

Carr,

Below are a few threads that may help.

454s and LT-1s use 2.5" pipe so the clamps will be larger than used on other engines. But are you saying the clamps on an automatic vs 4 speed differ? I know the automatic and 4 speed forward pipes are a bit different, but I've never heard that the clamps differ as well. Maybe a clamp expert will chime in...

https://www.forums.ncrs.org/showthread.php?61830-Correct-type-center-exhaust-clamp-for-1970

https://www.forums.ncrs.org/showthread.php?105550-Exhaust-clamps

https://www.forums.ncrs.org/showthread.php?96495-1970-exhaust-clamps

[Paul O.]

Re: 1970 BB Automatic Exhaust Clamps

Here is a Bowtie 1970 BB Auto.

[Gary B.]

Re: 1970 BB Automatic Exhaust Clamps

Close up of the same car.
GB

_DSC0046.jpg

[Carr C.]

Re: 1970 BB Automatic Exhaust Clamps

Thanks Gary, Paul & Mark!

[Gary B.]

Re: 1970 BB Automatic Exhaust Clamps

Gary, Paul,

Are those lock washers I see in the photo? In which case that differs from mid-year clamps for the front-to-intermediate clamp location which uses flange nuts. Also, are the threads still 5/16-18, as were the threads during the C2 era?

Gary

[Gary B.]

Re: 1970 BB Automatic Exhaust Clamps

Yes, they used lock washers under the nuts. Here's a better picture of the other side. This is from a 70, 8,00 s/n range. I have a 71 here now, pretty un-molested car, s/n 11,000 range, and it has flanged nuts on it. Was there a running change? Don't know. Paul might.

_DSC0046-1.jpg

All clamps, in my opinion, had 5/16" threads.
Later 72's used an open style clamp. Not sure when that change was made, but I'll enclose a picture of it also so if somebody search's years from now, it will be included.

_DSC0132-1.jpg

These also used a flanged nut, 5/16" thread.

Gary B

[Gary B.]

Re: 1970 BB Automatic Exhaust Clamps

Gary,

Do you have any of the AIMs for '70, '71 or '72? I don't know if one of those would call out the part number for the exhaust clamp nut or not. If the clamp consists of a unit of u-bolt, saddle, nut, etc., individual components may not be listed by part number.

Joe Lucia might know if/when the flanged nuts changed to regular nuts + lock washer.

Gary

[Paul O.]

Re: 1970 BB Automatic Exhaust Clamps

Gary,

Do you have any of the AIMs for '70, '71 or '72? I don't know if one of those would call out the part number for the exhaust clamp nut or not. If the clamp consists of a unit of u-bolt, saddle, nut, etc., individual components may not be listed by part number.

Joe Lucia might know if/when the flanged nuts changed to regular nuts + lock washer.

Gary

As far as I have seen the nut and lock washer is the normal setup. Now if Gary has an 71 with a nut with a flange that a first for me. We would need more cars with that setup to confirm that as a possible setup. I see that most of the time with reproduction clamps.

[Alan S.]

Re: 1970 BB Automatic Exhaust Clamps

Hi Gary,
I looked at the 71 AIM, UPC 8, Sheet A2, Exhaust System.
The base motor exhaust lists the U-bolt, Clamp, L. washer, and Nut, as separate items… with part numbers.
The Option Pages for the bb engines indicate that the exhaust system isn't illustrated and instructs one to look at the Parts List or Bill of Material for part numbers.
Regards,
Alan

[Gary B.]

Re: 1970 BB Automatic Exhaust Clamps

Alan,

Thanks for checking. I assume the 71 base motor uses a 2" exhaust system, so the clamp will be different. All C2 era cars used a 2" clamp at the tail pipe extension connection and that clamp used a lock washer. So, the 2" system part numbers don't necessarily answer the question about the 2.5" system flange nut vs lock washer.

Gary