cor66vette

Where can I find a "test pipe" to replace the cat on my '75?
Thank you

MelWff

remove the cat, gut it, and reinstall

COSPEED

Gutting results in a poor flow through due to the opening into a large area and back down again, but does the trick if not concerned with performance. I don;t think many are available anymore due to regs, but a 1975 will have the "bead" style of cat and they clog easy. Replace with a good ceramic style replacement or put in a custom pipe.

:thumbsup:

derekderek

that cat is the first cat ever made. it has the most platinum of any cat. highest scrap value of any cat. as long as you are deleting cat (i hope historic or whatever tag is emissions exempt) dump the y-pipe and run dual exhausts. call scrap yards and ask them what that cat is worth.

cor66vette

I hadn't thought of that option. Thanks.
I'm not so concerned about performance, but I would rather install a pipe but I'm having an issue locating a test tube for this. Thank you.

Thanks. I'm okay with state emissions testing- there is none, that's why I want to by-pass the cat. I have been thinking about dual exhaust for a while, and might do it down the road.

mikem350

If you want to "drop your beads" you need to remove the plug on the cat. I would try it with the cat on the car. Needs I think a 3/4 hex bar stock. Good luck after 40 yrs.

Years ago I bought a "test pipe" from JC Whitney

COSPEED

Correct! Don't see many to scrap anymore!

The OP is lucky to being a State w/no testing.

Snoopysvet

I have a used one. Send me a PM if interested.

terry82

you will notice a big improvement .

Jud Chapin

FWIW, that particular cat fits other Vettes and Camaros. At a minimum, the '76 Vette and '79 Camaro. I had these three cars and the cats were identical so they probably fit many other GM cars.

cor66vette

Thanks, guys for the input. My main objective is to do away with the cat and put in a straight pipe in its place, however, if I can gut it, I'll do that and see how it works. I don't know if it's any good. I know the cover shields came loose, so who knows what's going on inside that thing.

What is the best and easiest way to gut it, and how will I know it's completely gutted?

COSPEED

mikem350 describes a bit. With the old "pellet" style they have a fill plug on them, and it is extremely hard even back when they were new much less after all these years of corrosion, but a long breaker bar and the correct sized allen socket will allow you to remove the plug and dump out the pellets/beads, but if you try to gut it like a more modern honeycomb style you will most likely end up clogging it with the different chambers inside getting crushed together. Best is get a pipe made. Not difficult. Remove that old unit and measure and make a drawing of what you need and most exhaust shops should be able to make one cheap.

terry82

take off cat. take any metal rod beat out the clogged up crap.it comes right out .put it back on .I know off 10 cars just like this .

COSPEED

That does not work on the old style cats from the mid-late 70's, only on the honeycomb ceramic style newer ones.

cor66vette

I'll be going the test tube route. Done once and for all.

derekderek

Looks like it would be pretty easy to cut the ends off cat and buy a pipe with slight bend or flex piece and weld or clamp it in to make a "test" pipe. And you still have a big cat to sell for scrap...

cor66vette

That's exactly what I plan to do.

COSPEED

Bingo!! Good solution!

cor66vette

Will a test pipe for a 76 - 81 fit a 75?

EDIT* According to Eckler's the 76 - 81 cat will NOT fit a '75

Snoopysvet

http://www.siliconeintakes.com/produ...roducts_id=320