First I live in California so I'm somewhat limited what I can do legally.

I am looking at replacing my stock exhaust manifolds with a pair of headers. I’m looking at helping with performance and sound around town.

Will it make that much of a difference in performance with the catalytic converters still installed?

• I’m seeing a lot of used headers for sale for 79 and 80 vettes. Are there a difference between the years that I have to be concerned with when looking at purchasing a used set?
• Are there differences in models that will make a difference? That is would it be worth buying a specific model rather than just a set off the web.
• Any gotcha’s I should be concerned with?

Thanks

 

Stock 81s ran 2-1-2 exhaust with only 1 cat. Unless your prepared to upgrade to real duals with 2 performance converters I would leave it as is. I could be wrong, but I don't see much gains from adding headers to a stock 81 exhaust system. I'm no expert so maybe somebody has a better answer.

 

****PROFESSIONAL OPINION*****

1981 Corvettes already have a tubed header design manifold.

Depending on what you plan on buying...where if In California you still need to have the A.I.R. tubes coming out of the headers to connect to your air management valve system and smog pump.....so be aware of these tubes.....or you might regret it. So the design of the header DOES make a difference.

You will get somewhat of a gain...but to be honest. take your car to a performance shop with a chassis dyno and see what it is doing for horsepower and torque...and then do it again when you get done. Or don't. Your choice.

Depending on the design and configuration of your header...when it comes to getting the rest of your exhaust system to connect to it. It will more than likely need to go to an exhaust shop. AND....seeing that your transmission crossmember was designed to allow the exhaust to run under it on the right side....the left side ( drivers side) of the exhaust will need to be custom bent to it can then Siamese right along with the right side exhaust tube and fit in the area provided. Using an approved catalytic converter that has a 2 in-2 out design will allow these tubes to run side by side with each other.

Make sure that you system allows for the Oxygen sensor also.

If i am not mistaken...but I believe that your current factory catalytic converter has a tube that comes off the side of it that goes up to the engines air management/smog system. The catalytic converter you use should also have this same tube.

Keep in mind any support brackets and rods that attach to your exhaust manifold bolts....these SHOULD be retained and used....so modifications will more than likely need to be made so these brackets/rods can be used....and this can be a pain in the backside getting that figured out.

Spark plug wiring and routing may be effected.

It might be in your best interests...before you do anything....is to drive your car and get it hot and use an infra red thermometer and take temperature readings where your fuel lines on the frame are located near the exhaust....so you have a baseline reading. SO....if for some odd reason IF you have a problem when you drive your car for an hour or so...and it starts to act up...you can check this area again and see if the temperatures are higher due to the headers are adding more radiant heat to the fuel line and frame area.

DUB

 

I believe in CA you will need to make sure the headers you put on have an executive order on file with air resource board. To pass smog. The ARB website has searchable list of aftermarket parts with the executive order. There is a lot of stuff out there but only a few that have executive orders for those of us that still have to smog our cars.

 

if you have a stock cat now replace it .many new cats are very good .they are not restrictive like the 1981 cat is.change the cat then get better flowtru mufflers .