1978 Performance Upgrade Considerations
Thread Starter
3rd Gear
Joined: Jun 2023
Posts: 3
Likes: 0
1978 Performance Upgrade Considerations
I have a 1978 coupe that came with a gm good wrench/target master replacement engine. This did not concern me because I plan to do some performance upgrades plus my understanding is that numbers matching isn’t really a big deal in later c3’s. I understand that originality is desirable but that is not what I’m interested in in this case. I don’t live in California. My state has emissions testing but cars older than 1995 are exempt from testing. I realize that there are federal laws and I don’t plan to remove the converter, but some comments by a tech guy at Summit regarding potential issues with traffic stops has got me concerned about changing anything. It seems like many have upgraded performance (crate or otherwise) on later 70’s cars and as far as I know crate engines don’t come with emissions stuff that was stock in 1978 like smog pumps. Also many times performance upgrades usually don’t “look stock” especially if you need a non stock air cleaner to get hood clearance. Does anyone have any insights to share on this?
Instructor
Joined: Feb 2017
Posts: 136
Likes: 28
From: Liberty Island
What state is your car registered in?
i would not be worried with roadside stops out side of California.
what is by the book legal and what one can get away with are different . For example side pipes on any car that had a catalytic converter would not be legal… for road use.
i think most states are concerned with newer cars and the common road vehicles when it comes to emissions and then safety when it comes to older vehicles that get driven leas. There are alot of old cars with out egrs, A.i.R systems etc but far less older cars running around.
i would be real curious to see the emissions out put on a stock 78 C3 and an LS swapped 78 c3 without cats.
i would not be worried with roadside stops out side of California.
what is by the book legal and what one can get away with are different . For example side pipes on any car that had a catalytic converter would not be legal… for road use.
i think most states are concerned with newer cars and the common road vehicles when it comes to emissions and then safety when it comes to older vehicles that get driven leas. There are alot of old cars with out egrs, A.i.R systems etc but far less older cars running around.
i would be real curious to see the emissions out put on a stock 78 C3 and an LS swapped 78 c3 without cats.
Last edited by The Grinch; Jun 18, 2023 at 03:55 PM.
Melting Slicks
Joined: Jul 2019
Posts: 2,294
Likes: 2,015
From: MA/NH Seacoast
Just do what you want. Nobody is checking anything, especially if the vehicle doesn't need to pass any emission testing. A good set of heads, healthy cam, good intake and long tubes will wake up that 350. There's really no point in trying to improve the performance of the engine if you're gonna make it breathe through that horrible stock y-pipe and pellet cat. It's like trying to run a marathon while breathing through a straw.
Hell, even my new vehicles get bigger cams, long tubes, no cats etc etc and still pass inspection.
Dont overthink it.
Hell, even my new vehicles get bigger cams, long tubes, no cats etc etc and still pass inspection.
Dont overthink it.
