how to spot a aftermarket catalytic converter?

In addition to the arrow, look for wording (such as a brand name) indicating that it's not OEM.

But the best advice is: get real good at IDing them real quick. Find something with pictures to use as a guide. You can lose a lot of money in no time just by making a couple wrong guesses. Shop owners do not necessarily tell you wrong - they may not realize an aftermarket was put on a few years ago. Just saying it "came off of '89 Cadillac Eldorado" doesn't mean a thing.

In my experience I find a lot of aftermarket ones will have spot welds around the seam.

And look online for some buyers who have an online catalog with pictures and prices. Use as a reference.

Ahh Gents.. Yes the "FLOW" may give it away.. but some GM "Round Bread" and "XBody2" converters have FLOW stamped on them- and they are OEM. Reason being- they are so symmetrical that if they got on the parts car backwards in the factory.. car no runny runny right.. So yes Flow is usually a good determination.. but not always!!

Originally Posted by Focker

I have already told you to send me some pictures lol.

Me send you pics? Or the OP?

Aftermarket cats will usually have markings like N/CA, CA/TA or something similar. Many also have a manufacture date stamped on them (02/06, etc.). Some can be tricky to ID until you get very experienced with handling converters. Then, there are some good OEM cats that look like they would be aftermarket. Some round Nissans and Fords have no heat shields and no numbers or markings from the factory, but they are good OEM cats.

If you're ever unsure on a converter, make sure you're set up with your buyer to text pictures to them for a positive ID. Any good converter buyer will provide this service. That way, you won't get stuck paying good money for a $5 aftermarket, and you will also know that you didn't accidentally buy a good cat as junk.

Sparrow-
Long Time no see man. My core buyer will gladly do this for me as well. I appreciate that he does.. and once it is cut off- he already knows what is coming his way!

Originally Posted by SparrowMetals

Aftermarket cats will usually have markings like N/CA, CA/TA or something similar. Many also have a manufacture date stamped on them (02/06, etc.). Some can be tricky to ID until you get very experienced with handling converters. Then, there are some good OEM cats that look like they would be aftermarket. Some round Nissans and Fords have no heat shields and no numbers or markings from the factory, but they are good OEM cats.

Funny you say that Sparrow, but yesterday I scrapped a '97 Ford Cougar XR7 with the 4.6L V8 2 pre and one 3 way cat, they all had the date stamped 06 04 97, thought that was cool. Still got $110 for them. Also they were pretty hard to cut, double wall pipe.

Don't get me wrong I respect your opinion and enjoy your posts, but I am sure they were OEM.

I'm glad you mentioned that, Dave. Yes, many OEM Ford cats are stamped with a manufacture date. These will have the full date like yours did, as opposed to just a month and year like some aftermarkets do. They also have a small Ford logo on them near the date, which is a dead giveaway that they're good ones. I've seen dates on some other OEM cats as well- Volkswagen, Audi and Saab that I can think of.

You can usually spot a Ford cat from a mile away. They just have that very distinctive heat shield style.