The 1947 - Present Chevrolet & GMC Truck Message Board Network







Register or Log In To remove these advertisements.

Go Back   The 1947 - Present Chevrolet & GMC Truck Message Board Network > 47 - Current classic GM Trucks > The 1973 - 1987 Chevrolet & GMC Squarebody Pickups Message Board

Web 67-72chevytrucks.com


Reply
 
Thread Tools Display Modes
Old 08-22-2017, 07:33 PM   #1
KMK454
Registered User
 
KMK454's Avatar
 
Join Date: Jan 2007
Location: USA
Posts: 442
Stock Exhaust and Cats

First post in a while! The truck is coming out of storage. I do not need to "smog" my truck, but would like to clean it up as if I had to smog it. Eventually this means getting the charcoal canister and other stuff refreshed, but the first (and easiest) target is the exhaust.

Right now, it has LMC manifolds into true duals (no cats) that dump beneath the bed. The truck is a 78 C10 305 V8.

I would like to get a stock setup with a cat(s), manifolds and proper exits like the truck originally came with. The LMC manifolds should be fine, but I'm at a loss for the rest. Does anybody make repro parts for this? Or would I have to have one fabricated based off the brochures and documents with the truck?

Thanks!
__________________
Kurt
Instagram: @kurtkphoto
1978 C10 Silverado
1991 Camaro B4C
KMK454 is offline   Reply With Quote
Old 08-22-2017, 11:54 PM   #2
LuvNLife
Active Member
 
LuvNLife's Avatar
 
Join Date: May 2010
Location: Crossville, TN
Posts: 127
Re: Stock Exhaust and Cats

It looks like Walker is a source, but their lineup isn't complete that I can see. I found the Y pipe for a single cat, the muffler for a single cat/tailpipe and the single tailpipe for a cat (they list separately for ones without a cat), but they only have what look to be generic cats. You'd need the mid-pipe to join from the cat to the tailpipe, and maybe a piece off of the Y to join to the cat; that's what I didn't see. I didn't see where any of their dual exhaust systems were set up to accommodate cats.
LuvNLife is offline   Reply With Quote
Old 08-23-2017, 05:38 AM   #3
Dead Parrot
Registered User
 
Join Date: Aug 2012
Location: Oklahoma City, OK
Posts: 759
Re: Stock Exhaust and Cats

I think 'as shipped' dual cats are a rarity, even in the performance car area. Finding one for a truck shipped as an 'economy' setup is unlikely.

Doesn't mean you can't do one, just it is unlikely to find a factory type setup.

If you are trying for close to factory correct setup, avoid the old style pellet type of cat. Those do rob power. Go for the newer honeycomb style.

Check your truck GVWR of your truck. Might never needed cats. HD trucks of that era avoided many of the emissions requirements. My 75 only had PCV and THERMAC. No cats, pumps, canisters, egr, etc by being classed as HD emission. Restrictions tightened in later years.
Dead Parrot is offline   Reply With Quote
Old 08-23-2017, 09:33 AM   #4
CSHADES
Registered User
 
CSHADES's Avatar
 
Join Date: Nov 2015
Location: portage wi
Posts: 244
Re: Stock Exhaust and Cats

a 78 c10 would have had a cat under it. If you cant find the parts on the shelf to put it back most muffler shops can bend and install what you need including a y-pipe. I have done a few of these in the past. Used cats are not legal to be installed unless they have been tested, you wouldn't want to use the factory style cat any ways they will slow the truck down.
CSHADES is offline   Reply With Quote
Old 08-23-2017, 10:07 AM   #5
Peter S
Registered User
 
Peter S's Avatar
 
Join Date: Feb 2017
Location: Westfield, MA
Posts: 16
Re: Stock Exhaust and Cats

Not all 1978 half ton trucks came with cats. Mine didn't whereas my 1979 did have one. What determined if it had a cat?
__________________
-Peter


1978 K10 stepside
Peter S is offline   Reply With Quote
Old 08-23-2017, 04:37 PM   #6
Tom
driving is in my blood
 
Tom's Avatar
 
Join Date: Dec 1999
Location: Mesa AZ
Posts: 4,546
Re: Stock Exhaust and Cats

Same here, my 78 did not have any cats from the factory, 79 did. Both 1/2ton 2wd regular cabs.
__________________
-78 c10 short/step: 388cid, M20, 5/5 drop, lots more. Playtoy and first vehicle.
-98 c1500 x-cab: 5.7L, 17" rims, 5/6 drop, flowmaster, helper bags,NBS rear disk brakes.
-06 CBR600F4i: 110mph in 2nd at 14,000rpm= happiness.
DISCLAIMER: I cant spell for the life of me.
Tom is offline   Reply With Quote
Old 08-23-2017, 11:10 PM   #7
ray_mcavoy
Registered User
 
Join Date: Nov 2009
Location: Sherman, ME
Posts: 1,847
Re: Stock Exhaust and Cats

Quote:
Originally Posted by Peter S View Post
What determined if it had a cat?
It was based on GVW (Gross Vehicle Weight).

From 1975 up through 1977, anything over 6,000 lbs. GVW was considered heavy duty (for emissions purposes) and didn't require a catalytic converter.

1978 still used the 6,000 lbs. limit except California where it was 8,500 lbs. For 1979 the limit was raised to 8,500 lbs. for all states.
ray_mcavoy is offline   Reply With Quote
Old 08-24-2017, 12:57 AM   #8
Pyrotechnic
Registered User
 
Pyrotechnic's Avatar
 
Join Date: Feb 2007
Location: Austin and Kingsville, TX
Posts: 3,919
Re: Stock Exhaust and Cats

On an unmolested truck of that year, the transmission crossmember will tell if it came with a catalytic converter or not. The catalytic crossmember has a huge open area on the drivers side to allow for the catalyst. If the crossmember is symmetrical on both sides, it's a heavier GVWR truck that didn't have it.

Check out the link below, that should be the correct exhaust system for your truck and it looks like Walker makes everything you need.

http://www.rockauto.com/en/moreinfo....030330&jsn=727

And if your manifolds aren't correct, these should be the right ones:

http://www.rockauto.com/en/moreinfo....030330&jsn=738

http://www.rockauto.com/en/moreinfo....030330&jsn=739
__________________
1977 GMC Sierra Grande
Pyrotechnic is offline   Reply With Quote
Old 09-10-2017, 07:24 PM   #9
Pontiac1976
Registered User
 
Pontiac1976's Avatar
 
Join Date: Oct 2015
Location: Ottawa, Ontario, Canada
Posts: 188
Re: Stock Exhaust and Cats

I doing all most same set up I will be using duel's ex pipes set up. I got new 2014 cat's off a camero. 1977 w/ 82 305, no smog pump. all the rest is 77-84.
Walker makes single ex. If you want dual's your going to have to look in to the 72-74 car's that had duals use parts of it. If you want a set pre-made or get muffler shop to make one.
If your duel set is still good all you have to do is get muffler shop to cut pipes put in cat's.
if your tail pipes come out like a " L" behind the tires they should be good
Cats try
http://www.walkerexhaust.com/catalog...mension-search
__________________
1977 REG cab Long Bed with a 1984 Front Clip, 82 305 .60 over 9.0.1 flat top pistons, 4bbl , w/84 SS-intake & cam , w/ 1977 big block rad, 1975 gear box, 1984 master w/ metric fittings top & SAE fitting @ portion block, 1975 3.42 gear open diff. Duel 77-87 Factory air cleaner, duel inlet from rad support . Down sized 9' to new 8' Steel flat bed
Was a 77 454 w/308 gear. Taken out 550 lbs. up front with motor clip change.
Pontiac1976 is offline   Reply With Quote
Old 09-11-2017, 09:09 AM   #10
HunterRotten
Registered User
 
HunterRotten's Avatar
 
Join Date: Oct 2016
Location: Kentucky
Posts: 253
Re: Stock Exhaust and Cats

I'm a little late to the party but my 1978 had catalytic converter information stickers on the core support and on the driver side sun visor, I also had a big shield that was supposed to protect it I suppose but I took that out a long time ago. That walker stuff seems pretty cool, never heard of it or thought of putting "stock exhaust" on.
HunterRotten is offline   Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -4. The time now is 06:51 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Copyright 1997-2013 67-72chevytrucks.com