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So I had a little time to mess around with CAD yesterday. My wife was in a bad car accident on Wednesday. She'll be okay. So I took yesterday and today off work to get things sorted. But it was nice to have something to focus on in-between phone calls with body shops, police and insurance companies. Anyway after a few hours this is what I came up with. It took a lot of YouTube videos to learn how to make this in CAD.
I ordered the oval tubing yesterday. So as soon as the flanges come in I'll make a jig to hold everything together for welding. Next I need to get my hands on a 86-91 cat to get measurements off of. Then I can have that flange made. I already have a shop lined up for the ball end of that one.
If I would have known that these things weren't for sale someplace I would have been making these and selling them a long time ago. Once I get the first one made I'll need one of you guys to be my guinea pig being that my 84 hasn't had a cat in 20 years. So if someone wants a test pipe for a 82-85 for the cost of materials and shipping please let me know. All you would need to do is report back to me with how well it fit.
I bought a new corvette in 1978. I bought and installed a "test pipe". I don't remember if it made any difference or not. Dan
I don't know that most people install these trying to add power. I suppose it would a little. But the big reason is when you are trying to get a tune right it's easier to start rich and back off the timing. Then gradually pull fuel and add timing until it stops adding power. This is obviously easier on a dyno. But either way it's really easy to destroy a cat with excess fuel while tuning. So a test pipe will allow you to get a tune right and then put the cat back on after it's tuned. Or if you want the sound of no cat.
But I would love to see a dyno result of a test pipe vs stock cat.
The best trick to do is to use the old catalytic converter's housing with the "guts" removed. With the catalytic housing being in the car, you can claim ignorance and they will assume it is working. I would even fix the body of the catalytic and make it sealed up. The drone is not as big a problem when you have the catalytic converter there. With a test pipe the "drone" can/will appear just as it does with fancy exhaust systems without a Catalytic converter. The tube in place of a catalytic converter will raise questions and likely catch more attention of any inspector worth his weight.
I put a higher flowing catalytic on my C4 and it runs nice and clean while making more power and staying legal. I don't think the emissions rules will be going away any time soon.
I have 2 thirty year old exhaust systems made out of Aluminized Steel and they are still working great. I have no idea why anyone would pay extra for a metal that you don't need. It doesn't make your car any faster and it costs way more than the Aluminized Steel. It doesn't rust??
Cats probably the least restrictive part of the exuast system if its in proper working order. The early exhaust systems are... how do I say it nicely. ****.
Honestly it's pretty entertaining seeing how dumb the general population is day to day.
Well the flanges came in the mail today. They turned out pretty good. If I order another batch I'll make the oval just a bit smaller so I get a better fit for welding. But as is it's not too bad. I should have a couple test pipes made this weekend. I already have a jig made.
Well I got the first one done. This one is for 84 and 85 Corvettes and will also fit 83-85 Firebirds and Camaros. The jig I made worked really well. The welds aren't perfect. But I don't own a TIG so they're the best I can do with what I have. The important thing is they won't leak and they're straight. I think a half inch might be a little thick for the flanges. But it won't hurt anything. Anyone interested in getting one cheap and being my guinea pig? Once I get some verification from someone here that they fit properly then I'm going to try and list them on ebay. Hopefully they don't take the listing down.
Now that I'm getting the hang of LibreCAD, this weekend I'm going to make a CAD file for the flange on the 86-91 cats. I'll get that CAD file sent off and cut out on a laser. But I wanted to get these ones figured out first.
The flanges for 86-91's are ordered. I only got a few because I want to see how they turn out before ordering a bunch.
@spaceweasel If you're still looking for a test pipe at a cheap price I would love for you to test fit one of these for me when I get one done. I would only charge you the cost of materials and shipping. I'm not sure what that would be yet but I'm guessing it would be under $80. I'll know for sure when I get a clear answer on the tubing.
Also anyone with a 86-91, do you think a stainless band style step clamp would work instead of a U bolt? I hate u bolts and always use stainless band clamps if I can. If you guys think there would be room for that style instead of the U bolt I'll include one with this test pipe to make it easier to take back apart. This is a picture of what I'm talking about.
The EPA cracked down on the manufacture of emissions defeat devices quite a while ago. Technically, if a vehicle was built with emission controls it is illegal to remove them regardless of the age or use of the vehicle. Hence the disappearance of the "test pipe."
You're going to have to make your own.
EPA Officially Ends All Emissions, Ends Endangerment Finding, The Climate Scam Is Over!
