I have two catalytic converters on my '78 SA CORVETTE..One is rattling and both are shot..(Probably originals with 58K miles)
Car has SP plates which in Oregon allows driving for meets and shows up to about 3K miles a year..No renewal of tags ever and no emissions testing required.

Anyhow, muffler shops cannot remove them for good because of federal regs..( DUMB REGS).

I'd like to remove them and have slightly offset exhaust pieces seam welded back of headers to exhaust pipes and rear mufflers-tailpipes.
What's a good way to get this done..I'm not a welder..Any thots?Thanks, Jim

 

First off, having 2 cats with duals is technically illegal according to the beloved Feds, since the car originally came with a 2-1-2 exhaust with a single cat. Duals are not legal as ridiculous as this rule is. I would remove the 2 cats, put a cheap flexible pipe to run from the header collector to the exhaust pipes on each side and drive to a muffler shop to weld in a rigid pipe to connect the headers to the pipes or just drive with open exhaust to a shop to have the same done. With the cats already removed when you get to the shop, you should be good to go...

 

Or remove the cat, and beat the biscuit inside to pieces and pour it out, then replace. If I remember right, some of the earlier GMs used ceramic pellets and you could remove the screen that retained them, and pour them out. When I was younger, I had a 82 280Z. I used a 1 1/2" paddle bit with an extension to dig out the ceramic biscuit, then replaced the hollowed out shell of the cat to pass (pre sniffer) the state inspection.

 

Remove the catalytic converters and go with a true dual exhaust system with an H pipe and mufflers. This is what I have on my 1978 Pace Car and I love it. It sounds good and has more horsepower.

 

v[QUOTE=jim in oregon;1591842857]I have two catalytic converters on my '78 SA CORVETTE..One is rattling and both are shot..(Probably originals with 58K miles)
Car has SP plates which in Oregon allows driving for meets and shows up to about 3K miles a year..No renewal of tags ever and no emissions testing required.

Anyhow, muffler shops cannot remove them for good because of federal regs..( DUMB REGS).

I'd like to remove them and have slightly offset exhaust pieces seam welded back of headers to exhaust pipes and rear mufflers-tailpipes.
What's a good

Jim, new member, first reply, I have a 79 that had the 2-1-2 original system. I cut the whole thing apart and removed everything, cylinder heads back. Bought a used set of long tube headers off Craigslist or ebay (don't remember) for cheap, and a new complete dual system for a 68 427, 2 1/2," ebay for $257. I cut off the front part off the new pipes and fabricated short sections to connect to the headers. Then I removed the spare tire holder and mounted a single dual outlet muffler, 3" out, 2, 2 1/2" in, turned around for a single 3" out the rear, right in the center of the car. The muffler is backward from its intended use. Of course the 68 427 system is a true dual with no cats. I have never started the engine currently in the car to hear how loud it is because I am building up a 327, BW t10 prime mover to replace the 350, auto. I'm not saying it would be easy to go this route because it's not quite drop in but it wasn't too hard.

Allan aka gluejones

 

Just buy new pipes from Corvette Central,they fit,priced right and are relatively easy to install.

 

HMMM..yes the car originally only had one catalytic converter..So technically it's illegal already for the street here close to Portland Oregon..

Has good well tuned-fitted performance headers now and stainless exhaust back to quality mufflers and dual tailpipes..NO crosssover H or X configuration..

Nothing wrong with the exhaust system other than the aging cats..

I've read up a bit on flexible pieces and they seem to be a temporary fix..
Shucks maybe I'll have a friend use the cats as a pattern for the slight offset.....to get some stainless slip on pieces less than 20" total.. bent and then seam weld them up nicely..
He has a lift and can cut the cats off.or maybe have another gearhead friend install some manual cutouts and tune accordingly..

I grew up close to a dragstrip when the strokers and gassers used to run at night..and love the sound of a good engine running right..loud enuf I can't hear conversation (have bad hearing anyhow..
or bother with the radio or CD..or CB..

decisions-decisions..Thanksall for your thots..Jim

 

Just as a point of reference... Back in the late 70's, a friend ad I both had '77 Corvettes we had bought new. They were both bone stock L48's with automatics. Both would top out at about 125 mph.

Back then you could purchase a "test pipe" from almost any of the vendors that would install in place of your catylitic converter to ostensibly see if your converter was blocking exhaust flow and needed replacing. We both installed them and discovered that our cars could reach 130 mph with no other modifications.

I seem to recall that our converters found their way back on the cars when they were sold...

Good luck... GUSTO

 

I had the Cat test pipe on my 78 in 1983 in place of the pancake GM cat....until the car became exempt from testing...then I went to true duals

 

A quick update on this older post of mine.Found a welder who cut-removed the old cat converters on my 78 and installed two stainless steel 2.25" exhaust pieces and seam welded all nicely..less than 100 dollars and done in 2 hours..Another small matter successfully resolved..Jim