Which of the '73-'80 Chevy's had catylitic converters and which didn't?
 

I am sort of lost here, I have 4 buddies that have '73-'80 Chevys and half of them have cats and half don't. The ones that don't have them are a '78 Camper Special with a 350 and a 4-speed, and the other one is a '74 C10 short bed with a 350 and TH350 trans. The ones that have cats are a '75 C10 "BIG TEN" short bed with a 350 and TH350 trans, and the other one is a '78 C10 short bed with a 350 and TH350 trans. Why do some of them have catylitic converters and others don't.
I have a neighbor who had an '85 C20 scottsdale that came with a 6.2 diesel, but it was replaced with a 350. He doesn't have to go through emisions because it was a diesel. I am thinking about picking it up and dropping in a stout big block, with a carb and no emisions controls.

Thanks,
Erik

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'29 Chrysler model 65 all original, 2nd owner ***FOR SALE***
'63 Impala SS 283, 3-on-the tree, flowmaster 2 1/4" dual exhaust, performer intake, edelbrock 600 carb, chrome 15x8 rally's
'64 Impala 4-door 126,000 miles, we just got from original owner, shes 93.
'65 Impala SS, built 332, 700R4, 3.73, 2 1/2" mandral bent duals w/H pipe, Flowmaster 40-series deltaflows, MSD Mallory, too many modifications to list
'72 Chevy Suburban 4x4, NP205, TH350, balanced 357 (.040 350), 268 high energy cam, 9.2:1 comp, 1.94/1.50 heads (ENGINE BUILT BY THE GREAT RAYZOR or if you know him RAY, WHO POSTS ON THIS BOARD AND CHEVYTALK), 3/4 ton leaf springs, 4" lift, 35/12.5/16.5 Grabber MT's, Rancho shocks, Rancho dual steering stabalizer, American Eagle 143's 16.5x9.75 6 lug, 4.10's, 12 bolt rear limited slip, Dana 44 front limited slip. Carter 600, performer intake, headers and flowmaster exhaust system very soon.
'95 Impala SS Flowmaster cat-back, K&N, 285/40/17 Firehawks, Dark cherry metallic, 27,000 miles, extreamly fun vehicle
'95 Chevy K2500, ex-cab, long bed, 350, AT, Flowmaster cat-back, 265/75/16 Mud Kings, 16x7.5 Centerline HT cast
wheels, Leer high rise canope, bed liner w/ mat, loaded.**FOR SALE**

Hi,
I'm not quite sure, but I think that'73 was the only year that they didn't come with cats, maybe '74 too. Ithink after that they were required by the government to have them. Up here in ND, though, I would say that over 90% of these older trucks have had the cats removed by their owners. I know that mine started on fire and had to be removed 19 years ago... I'm not totally sure on this, but that's how I remember it being, there might be exceptions...

Eric

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'80 Chevy Cheyenne 1/2 350 4bbl.

Hey Eric,

I wonder why my friends '78 camper special doesn't have cats? He said it still has the original exhaust system and I looked under there and saw there are no cats. I wonder if since its a heavy duty truck it wasn't required to have converters.

Thanks,
Erik

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'29 Chrysler model 65 all original, 2nd owner ***FOR SALE***
'63 Impala SS 283, 3-on-the tree, flowmaster 2 1/4" dual exhaust, performer intake, edelbrock 600 carb, chrome 15x8 rally's
'64 Impala 4-door 126,000 miles, we just got from original owner, shes 93.
'65 Impala SS, built 332, 700R4, 3.73, 2 1/2" mandral bent duals w/H pipe, Flowmaster 40-series deltaflows, MSD Mallory, too many modifications to list
'72 Chevy Suburban 4x4, NP205, TH350, balanced 357 (.040 350), 268 high energy cam, 9.2:1 comp, 1.94/1.50 heads (ENGINE BUILT BY THE GREAT RAYZOR or if you know him RAY, WHO POSTS ON THIS BOARD AND CHEVYTALK), 3/4 ton leaf springs, 4" lift, 35/12.5/16.5 Grabber MT's, Rancho shocks, Rancho dual steering stabalizer, American Eagle 143's 16.5x9.75 6 lug, 4.10's, 12 bolt rear limited slip, Dana 44 front limited slip. Carter 600, performer intake, headers and flowmaster exhaust system very soon.
'95 Impala SS Flowmaster cat-back, K&N, 285/40/17 Firehawks, Dark cherry metallic, 27,000 miles, extreamly fun vehicle
'95 Chevy K2500, ex-cab, long bed, 350, AT, Flowmaster cat-back, 265/75/16 Mud Kings, 16x7.5 Centerline HT cast
wheels, Leer high rise canope, bed liner w/ mat, loaded.**FOR SALE**

Hey Erik,

It's a posiblity that they didn't require the heavy duty pickups to have cats on them. I don't really know anyone that has a heavy duty pickup. I do know that my '80 Big Ten C10 had one from the factory though. Around here no one is really concerned where or not their pickup is supposed to have a cat, they just take them off anyway....

Eric

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'80 Chevy Cheyenne 1/2 350 4bbl.

ALL '75-up trucks have them. How does he know the '78 is all orignal on the exhaust, those pipes cant be 23 years old and still be on the truck.
Has he owned the truck since new ?

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Its all going.... selling/scrapping everything ! Anything I have, its for sale, even the new oxy/acetylene torch set-up
Randy

5470 posts 4-30-01
http://communities.msn.com/RandyR72K5
1968 LWB C-10
1972 CST 4x4 K-5
Lincoln, IL
"life's gonna leave me in the dust, if I don't try and catch up to it soon"
r72k5@hotmail.com
[EMAIL]

It only has 70,000 miles on it. He is the second owner, but he got it back in '80. It was all original then and still now, except he put 33/12.5/16.5 Bridgestone Desert Dueller out back. Other than the tires its all original and in outstanding condition.

Thanks,
Erik

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'29 Chrysler model 65 all original, 2nd owner ***FOR SALE***
'63 Impala SS 283, 3-on-the tree, flowmaster 2 1/4" dual exhaust, performer intake, edelbrock 600 carb, chrome 15x8 rally's
'64 Impala 4-door 126,000 miles, we just got from original owner, shes 93.
'65 Impala SS, built 332, 700R4, 3.73, 2 1/2" mandral bent duals w/H pipe, Flowmaster 40-series deltaflows, MSD Mallory, too many modifications to list
'72 Chevy Suburban 4x4, NP205, TH350, balanced 357 (.040 350), 268 high energy cam, 9.2:1 comp, 1.94/1.50 heads (ENGINE BUILT BY THE GREAT RAYZOR or if you know him RAY, WHO POSTS ON THIS BOARD AND CHEVYTALK), 3/4 ton leaf springs, 4" lift, 35/12.5/16.5 Grabber MT's, Rancho shocks, Rancho dual steering stabalizer, American Eagle 143's 16.5x9.75 6 lug, 4.10's, 12 bolt rear limited slip, Dana 44 front limited slip. Carter 600, performer intake, headers and flowmaster exhaust system very soon.
'95 Impala SS Flowmaster cat-back, K&N, 285/40/17 Firehawks, Dark cherry metallic, 27,000 miles, extreamly fun vehicle
'95 Chevy K2500, ex-cab, long bed, 350, AT, Flowmaster cat-back, 265/75/16 Mud Kings, 16x7.5 Centerline HT cast
wheels, Leer high rise canope, bed liner w/ mat, loaded.**FOR SALE**

Someone has removed the catlytic converter.

Most trucks over a certain Weight (Towing) is exempt from Cats. 3/4 tons I have seen didn't come with them. '75 was the first year for catalytic converters and you can be sure it had them if it has "unleaded fuel only" on the fuel guage and it has the small throat fuel filler. Some 75 had them, some didn't. Everything 1/2 ton after it had cats. As for the Camper specials, due to the load capacity, they were possibly exempt.

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Chris Lucas
1973 Chevy C-10
1975 Chevy Silverado
Captkaos' Page

I have a 77 1/2 ton with a 350 auto and no cat, It did not come with one as the underhood sticker says nothing about catalyst or AIR. The only emission equipment it has is an evaporative canister. This truck is considered Heavy Duty because of the GVW (6700 I think)

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Rick
Broken Arrow, OK
72 cheyenne (in pieces)

My father's 79 20-series crewcab camper special 454 had cats, A.I.R, smog pump, EGR, unleaded fuel, charcoal canisters, 2-into-1-into-2 exhaust. You name it, it had it.

My buddy's '80 K20 Custom had a PCV valve and that's it. All factory.

I've heard 1-tons went right till 85 or so without any cats.

The bottom line is, it depends on how your truck was originally outfitted. There are at least three levels of emissions equipment I know of: Federal, California, and High-altitude. It seem the equipment for each level depends on the particular model year.

Even though this is an old topic, I am new to this board, and since I know the LONG answer to this question, I can't resist posting a response...Please bear with me!

Basic Federal (i.e. non California) emission laws are as follows for gasoline fueled vehicles:

For 1973 to 1978 all passenger cars and light trucks under 6,000 lbs GVWR must meet stringent light duty emission standards. All trucks heavier than 6,000 lbs GVWR must comply with heavy duty emission standards, which are much more lenient. For 1979 through the current day, the dividing line between light and heavy duty emissions was raised from 6,000 lbs GVWR to 8,500 lbs GVWR, forcing more trucks to comply with the stricter emissions standards than previously.

California emission history is identical with one exception: that state raised the heavy duty emission threshold for California-sold vehicles from 6,000 lbs GVWR to 8,500 lbs GVWR a year earlier, for 1978. (I.E. the Federal Government followed California's lead a year later, for 1979.)

A few other general facts:

Catalytic converters were introduced into the auto industry for the 1975 model year. From 1975 on, catalytic converters were used on ALMOST all light duty emission standard vehicles (all states) but were not used on any heavy duty emission standard vehicles. When auto manufacturers adopted fuel injection in their light and heavy duty emission class vehicles, they adopted the use of catalytic converters across the line. (GM adopted fuel injection and cats essentially across the line for 1987.)

...What all of the above means for 1973 to 1987 Chevy C/K series trucks follows:

For 1973 thru 1974, no converters on any models, anywhere.

For 1975 thru 1977, catalytic converters were used on all C/K 10/15 trucks nationwide with GVW's under and up to 6,000 lbs, except 1976 and 1977 C10/15's with the 454 V8. Models with GVW's over 6,000 lbs (i.e. all 1975-77 C10/15's with the F44/Big 10/Heavy Half, all 1976 and 1977 K10/15's and all 1975, 1976, and 1977 C/K 20/25/30/35's) did not use catalytic converters.

For 1978, all C10/15's with GVW's under 6,000 lbs have converters regardless of engine. All other '78 models (i.e. Big 10's/Heavy Halfs, K10's, C/K 20/25/30/35's)had GVW's over 6,000 lbs, and therefore did not use converters. EXCEPTION: For 1978, all California models with GVW's under 8,500 lbs had cats. Therefore, this California exception included ALL and ONLY 10/15/20/25 series vehicles, including Big 10's/Heavy Halfs.

For 1979, Federal laws, like California statutes in '78, raised the GVW threshold. So, all 1979 models, except for C/K 30/35 vehicles, had cats, nationwide.

For 1980 through 1986, the same models as those for '79 used cats. However, a new C6P heavy duty option was offered for C/K 20/25 models which provided an 8,600 lb suspension package. These new, heavier 3/4 tons cleared the 8,500 lb limit, and so did not use converters during this time period, nor did C/K 30/35's.

For 1987 and beyond, all Chevy/GMC fuel injected engines used cats regardless of location or weight class. Only a few 30/35 series chassis cab models offered carburated 292, 350 and 454 engines, and those were the only models that did not use catalytic converters for 1987 on.

Note: the above discussion applies only to U.S. vehicles. Canadian Chevy/ GMC trucks followed a much simpler story, I think. From what I have seen, no Canadian carburated Chevy/ GMC C/K/R/V used cats, while all '87 and later fuel injected models did.

End of story!

Interesting fact, I think in 2000, maybe 2001, the government passed that all light duty trucks have to meet passenger car standards.

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'69 G.M.C. 350/350. Trying to clean up the left over damage from the Dope-Smokin-Old-Man
I've been dubbed the Longhorn Freak/Fanatic/Expert, I just hope I can live up to it.
Need to pick up the one ton Longhorn with a PONTIAC 350/350soon.
Thanks every one!:)
Check out The Longhorn Webite.
If you need a pic posted, E-mail me at longhornmail@yahoo.com
Andy, in Columbus Ohio

KIILEW, You are exactly on the money about the cat thing. Having the opportunity to have owned C series and K series 10-20 series trucks in 77,78,and 79. Your info reflected what was on my trucks. Another piece of info is that trucks with cats had the words UNLEADED FUEL ONLY on the fuel gage. Trucks without cats did not say this. All my trucks were not california.

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Marty Hall
Taylorsville, Ky
1971 C-10 SWB fleetside (355,700-R4)
1971 K-10 LWB Cheyenne (454\turbo-400)
1972 C-10 SWB stepside (6-cyl)
1949 3100 chevy panel delivery
(original)
93 S-10 Blazer
93 S-10 Pickup

My 79 k/20 gvw 8600# had a cat.
My dads 79 F-150 that he ordered brand new and still owns had no cat,it's a 6 cyl.

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69 CST/10 350/400TH lwb fleet all original,1 owner
79 K/20 4x4 built & lifted
Sheridan,IN

sorry to bring back this old post guys, but I need to find out whether or not this truck came with cats. According to the above info, unless this is a heavy duty truck, then it required cats. I'm not sure if it is classified as heavy duty or not. It came with a tow package and a 454.

it's a 78 1/2 ton short bed. the vin is:

TCS448Z526228

Thanks in advance,
Dave

:p Here in Califronia, we DO have to worry about emissions crap. It sucks a big one.

I have a 1978 C-10 equipped with a 454 engine. It was built in the first part of 1978 and did not have a cat converter. It is not a California truck either. I believe in the latter part of the 78 model year, they added the gas doors and the cats, and other emission stuff. A good clue is the unleaded fuel only stickers on the dash and gas fill. Leaded gas is a no-no for cats (and felines too ):D

this link explains it all thanks swerve for the info

http://www.73-87.com/7387stuff/7387emislevel.htm

Thanks should go to KIILew. This is his info. I just put it on my site. The same info is also posted by him above.

you know i got a 1978 suburban its 6800 gvwr. it had no cat on it but im in the process of restoring it and going to go with a 383 stroker with a 700 cfm holley or maybe a stock quadrajet. i wonder how much emmission that motor will put out any tips on keeping the emmission down. Also i was wondering if any1 here is from tn or nashville for that matter i would like to meet up with some people and mayube share some ideas.

There is no "unleaded fuel only" on it anywhere, but I don't see how it would be a 6000lb truck either. It's kinda confusing.

nope no unleaded fuel anywhere i just checked when i saw this post and the door sticker says 6800 gvwr you got to remeber this a suburban not a truck its a bit more heavier.

I wasn't directing that directly towards you. I was referring to the information above that states what years had cats with exceptions for the heavy duty trucks. Sorry for the confusion.

Dave

In canada it went like this, all 73-75, no cats. 76 on, all had cats. This applies to all cars/trucks.

The cat question has undoutably been answered, but what about smog pumps?

smog pumps hardly ever seen on anything cept cars, at least int he 48 states other than cali, i cant recall seeing a 73-up with smog pump, i have a 79 big 10 bonanza 350 th350 out here its got a cat on it and is not cali truck

so..

WRONG! my '93 C1500 has a C3500 exhaust system from the "converter" forward. all factory GM stuff too, 3" y-pipe and my "converter" is a straight piece of 3" tubing. these are genuine GM parts that i ordered through GMSPO when i was working at the dealership. like Chris said before, it all has to do with GVWR.

You got a pic of it? I've got the same thing here.

My understanding is that on TRUCKS that 78 was first year for cats in the states Except Cali. I think Cali got them in 75.
On the core suport or the Air cleaner (it was on the air cleaner on my 75 Jimmy) there will be a sticker and if it had Cats it should say CATALIST accross the top and have the Gap and timing info on it as well. That sticker ended up on the core suport from I think 76 up.

Talk about bringing back the dead. :)

Here's some info from our friend KIILew, thanks again Ken.

----------------------------------------------------------

For 1973 thru 1974, no converters on any models, anywhere.

For 1975 thru 1977, catalytic converters were used on all C/K 10/15 trucks nationwide with GVW's under and up to 6,000 lbs, except 1976 and 1977 C10/15's with the 454 V8. Models with GVW's over 6,000 lbs (i.e. all 1975-77 C10/15's with the F44/Big 10/Heavy Half, all 1976 and 1977 K10/15's and all 1975, 1976, and 1977 C/K 20/25/30/35's) did not use catalytic converters.

For 1978, all C10/15's with GVW's under 6,000 lbs have converters regardless of engine. All other '78 models (i.e. Big 10's/Heavy Halfs, K10's, C/K 20/25/30/35's)had GVW's over 6,000 lbs, and therefore did not use converters. EXCEPTION: For 1978, all California models with GVW's under 8,500 lbs had cats. Therefore, this California exception included ALL and ONLY 10/15/20/25 series vehicles, including Big 10's/Heavy Halfs.

For 1979, Federal laws, like California statutes in '78, raised the GVW threshold. So, all 1979 models, except for C/K 30/35 vehicles, had cats, nationwide.

For 1980 through 1986, the same models as those for '79 used cats. However, a new C6P heavy duty option was offered for C/K 20/25 models which provided an 8,600 lb suspension package. These new, heavier 3/4 tons cleared the 8,500 lb limit, and so did not use converters during this time period, nor did C/K 30/35's.

For 1987 and beyond, all Chevy/GMC fuel injected engines used cats regardless of location or weight class. Only a few 30/35 series chassis cab models offered carbureted 292, 350 and 454 engines, and those were the only models that did not use catalytic converters for 1987 on.

Note: The above applies only to U.S. vehicles. Canadian Chevy/ GMC trucks followed a much simpler story, I think. From what I have seen, no Canadian carbureted Chevy/ GMC C/K/R/V used cats, while all '87 and later fuel injected models did.

i have a 1976 C 10 custom deluxe with a six cylinder and three on the tree and that bad boy has no cat from what i see most of them until 1977 had no cat ( according to the Walker Exhaust book)

does anyone know where this information came from? it appears to be incorrect. the exhaust for my '93 is for a C309(03) truck (1 ton, SCLB) with the TBI 350. there are definitely no cats involved. :confused:

KILLew,

I have a question for you regarding your info on 75-77 trucks.

You state that all had cats except 76-77 454 V8's. Do you mean 75-77? I've got a 75 silverado C10 with a 454, and I have no indication that it ever had cats. Also, it would seem odd to have 75 454s with cats, and then remove them for 76-77.

Thanks,

Brian

Dang, looking back through this very old thread, I see Ken posted exactly what I just did. Must of been where I copied it from. :)

I'm pretty sure Ken gets his info from GM publications. Not sure, but I think this is it.

As we all know, GM has done some strange things. They never were one to go exactly by a book anyway.

Why dont you run the VIN number through CARFAX? If It had a different engine in it when built that sight should tell you. It cost like $15 bucks to run it so if you dont want to do that, I have unlimited reports till May 30th or so. Reply or Email with the VIN and I will run it. Lawboybill@yahoo.com (in the subject line..please put CARFAX REPORT so I wont just delete it..I dont read emails from people I dont know.)

My 75 Jimmy is listed as a 6300lb GVWR. GM side steping and using a loop hole. :D

I know a bunch of folks with K5's and except cali models, it's rare to see a cat before 78.

I will add to the confusion. My 78 1/2 ton blazer originally had a 400, does not say "unleaded fuel only" anywhere, had no diagram on radiator support and had no cats. Its GVW is under 6000. It also has no smog pump or anything emmisions related that i can see, unless you count a PCV valve. My buddies 78 truck was identical. Both of these vehicles have resided in emmision counties of Utah for their entire lives. And his passed, hope mine will too:confused:

My 78 Chevy 1/2 ton has a GVW of 6,200 which gets it over the hump of requiring a cat. It also have factory dual exhaust according to the factory sticker in the glove box. Heat riser on the passenger side exhaust and PVC valve. Simple and keeping that way.

Bill

Well, I see this old thread has been opened, and since there are some interesting follow-up posts that seem to contradict my earlier writing, I thought I would write in again.

Mike (Swervin) is right about the source for my information. Most of this knowledge comes from original GM truck data and parts books and other factory literature, along with my own personal observation. Of course, he is also right when he suggests that, after all, GM doesn’t do everything “by the book.” And sometimes neither the books- -nor I- -am correct!

Regarding Brian’s (bpmcgee) note about the ’75 C10 454…
I am wondering what the GVW rating of your particular vehicle is, Brian. According to the 1975 factory literature, the under-6,001 lb application of the 454 does indeed have a catalytic converter. So equipped, the ’75 454 had a 215 horsepower rating. And yes, as odd as it seems, GM was able to recalibrate the under-6,000 lb 454 enough to pass light duty truck smog testing without the cat for 1976 and 1977. Horsepower improved as well, with a jump to 245. This output even exceeded the heavy-duty version of the same engine used in the 6,001-plus GVWR pickup and Suburbans, which was rated at 240 horsepower during ’75 to ’78 model years. When the 454 was again forced to wear the cat in ’78 under-6,001 pound models, the horsepower figure plummeted down to 205.

On the other hand, Brian, if your ’75 C10 has a 6,200 lb GVWR, which was optional at the time, then your 454 won’t have the cat. And if this is not the case, perhaps the ’76 light duty emission 454 recalibration I referred to in the preceding paragraph took place as a running change during the ’75 model year, which is not reflected in the literature I have.

Regarding alf444’s comment about his Blazer and that of his friend…
Everything you wrote is consistent with my understanding of this stuff except for one thing. I wonder what the GVWR plate of your Blazer states. The reason I mention this is because all ’76 thru ’80 K5 Blazer/Jimmy (4wd) models- -and K10/15 pickups- -were cataloged with 6,200 lb GVWR’s. This isn’t to say that I and the GM literature are infallible (I am far from it), but I am very curious!

Finally, regarding Jeremy’s (1FaastC10) retrofit 1993 C3500 exhaust system…
Your post has particularly piqued my interest. I wish I knew what the part numbers of your exhaust components were! I am wondering if the “straight pipe” intermediate exhaust pipe is actually from a 454 1 ton model. The reason I suggest this is that the ¾ and 1 ton 454 models for the ’90 thru ’94 model years placed the catalytic converter BEHIND the muffler. Perhaps the 454 straight pipe used in these applications could be fitted directly to the 350 y-pipe and muffler/tailpipe assemblies. Or perhaps your components are GM “off road” or export pieces. Or, maybe I am just wrong, although I am otherwise pretty confident about the accuracy of my original post. Admittedly, I have yet to acquire a GM original parts book that is specific to the ’93 model year.

Anyway, like I said- -interesting posts!

Ken

My 75 C10 SWB MIGHT have originally had a cat...I dunno now though...if you guys say that it will say "CATALYST" on the radiator core support Emissions sticker..then I DIDN'T originally have a cat, cuz my Emissions sticker only says EGR, EFE, and OC Exhaust". But I figured OC Exhaust meant a cat, but maybe it doesn't...:confused: