BBC Exhaust Assembly. Some info. for Randy500 & whomever

[71CHEVYSHORTBED402]

Oooops, forgot to mention this is a 71 402 C-10 with rear leaf springs.


This began from another thread. Figured I dedicate one, in case someone needs it. While I'm "restoring" this truck, I doubt I'll use any of these parts for a new system (not that they're for sale, yet anyway). The rubber bushings and soles are bad, stuff broken and pitted. Where would you expect to find replacements for a good restoration?

Anyway, below is the write-up. If you want to see more pictures then see post 11 here.....Thanks. http://67-72chevytrucks.com/vboard/s...d.php?t=742342

Exhaust pipe to manifold: The exhaust pipe flange slips over the exhaust manifold studs and is secured using three 9/16" brass nuts. The crest end of these nuts face the flange. The studs are 3/8-16.

LH front hanger:
• The LH exhaust pipe is secured with a U-bolt clamp hanger using two 1/2" flare hex nuts. The U-bolt threads are 5/16-18.

• This hanger secures to the front of the bracket riveted onto the frame using a 1/2" hex bolt and flare nut. The bolt thread is 5/16-18 x 1.1/4. A plate fits between the rubber sole and bolt head. The bolt inserts from the front.

RH front hanger:
• The RH exhaust pipe is secured with a band clamp hanger using a 1/2" hex bolt and nut. The bolt thread is 5/16-18 x 1.5. The bolt inserts from the top.

• This hanger secures to the front of the bracket riveted onto the frame using a 1/2" recessed flare hex tapered bolt and nut. The bolt thread is 5/16-18 x 1. The bolt inserts from the front. NOTE: The hanger has a rubber sole. It appears to be missing the plate to protect the sole from the bolt head, like what was on the LH side.

LH rear hanger: See RH rear hanger. NOTE: The rear hangers are not the same. One is for the LH side and the other for the RH side. Correct placement is the clamp is underneath the frame, not outside the frame, and it's tilted toward the rear.

RH rear hanger:
• From the front the hanger mounts as follows: 1/2" hex bolt (5/16-18 x 1.1/2) > bracket riveted to frame > rubber bushing > hanger > rubber bushing > thin washer > two 1/2" nuts.

• The exhaust pipe is secured to the U-bolt clamp using two 1/2" nuts. The U-bolt threads are 5/16-18.

Mufflers:
• Each muffler bracket uses two rubber bushings and a steel sleeve.

• Each bracket mounts to the inside of the cross member using a 1/2" hex bolt and washer. The bolt thread is 5/16-18. The bolt inserts from the rear. NOTE: The bolt lengths for each muffler varied. One was 3/4" and the other 1.1/2". 1" bolts are adequate.

• The top portion of each strap is secured to the bracket using a 5/8" hex bolt & 11/16" nut. The bolt thread is 7/16-14 x 2.1/4, of which 7/8" is shaft. The bolt inserts from the inside.

• The strap is tightened using a 1/2" hex bolt and nut. The bolt thread is 5/16-18 x 2.1/4, of which 1.1/4" is shaft. This is placed on the strap below the bracket.

NOTES:

The pipes to the mufflers are positioned to the front inside of the muffler. The pipes from the mufflers are positioned to the rear outside of the muffler.

Both mufflers are stamped 924306.

I believe a large majority of these parts are original, but not all. Edit: Not to mean this picture, the write-up. All the parts in the pic. are original. Always found it odd that, on occasion, you find a larger OD nut than the bolt head (muffler bracket/strap). GM's way to skip a washer in places, I don't know.

[randy500]

Thanks now I understand how the muffler hangars work!

[71CHEVYSHORTBED402]

Originally Posted by randy500

Thanks now I understand how the muffler hangars work!

Anytime dude. What kind of restoration are you doing? New truck or more better?

Ha ha...My wife......"I can't believe you're not done". That mostly means she didn't realize the extent what's left to take off. She might not be a project fan.. Ask me I'm close. A lot of parts to an A/C cab.

Edit: If you should find the right bushings for the muffler brackets, appreciate you letting me know. Other than that, I don't see what I'm re-using. Hopefully the exhaust guy uses existing frame locations. Then again, think I'll look for another LH rear hanger. Seems those bushings would be easy to replace.