I am looking to do a custom exhaust, and was wondering about the inlet and outlet diameters of the factory catalytic converter on my 1994 pickup with a 3.0

I read in another thread that they were 2", but the OP had the 22re and I wasn't sure if they're the same or not.

I was planning on going with a 2-1/4" custom exhaust, but if the cat is only 2" then I don't see a point in going with larger diameter piping. From what I understand the exhaust would be bottlenecked and the flow would be the same whether I used 2" piping or 2-1/4" because of the 2" cat. Feel free to correct me if I'm wrong...

Quite a few go with the custom exhaust from the cat back.

if you still have the factory cat it has flanges at both ends.

Go with a new universal cat with the diameter you want.

then you can go with 2.25 from the manifolds back.

dunno what it is on the v6, but on a 22re the stock diameter is only around 1.75" ID. when i upgraded last year I did similar to Wyoming's suggestion - went with larger diameter up close to manifold (2") then to a 2" ID high-flow CAT (can toss golf ball straight through - zero restriction), followed by 2.25" and through a round turbo muffler that is also see-through like the CAT. I don't see why something similar wouldn't work on a v6. it'll save you from buying headers at least

as for the stock CAT, like said - MANY people only upgrade CAT-back exhaust and leave their stock, 20+yr old, 200k+, clogged up CAT in there as the choke point. Why? because it costs more investment.

This does not answer the question(s) I was asking.

I do not want to go with an aftermarket universal cat; I want to stick with the stock one. I was asking what the outlet diameter is...or what the diameter is inside the cat.

I have read that an exhaust system will be bottlenecked by the smallest piece within the system - whether that is the piping before the cat, the cat itself, the piping after the cat, the inlet/outlet of the muffler, etc. Because of this, I see no need to go with piping larger than whatever the smallest pre-existing diameter is, assuming this claim is true...but if it is not true, then feel free to correct me.

My entire exhaust system was replaced by the previous/original owner less than 5 years ago...so it seems to be in fine condition.

I understand that an aftermarket "high-flow" cat should provide less restriction, but I have swapped exhausts on several of my cars in the past and EVERY one I changed or removed the cat on ended up having problems - CEL, rough/low idle, strong smells of fuel, etc.

I have learned after going through those headaches that it is better not to mess with the cat. And on that note - from what I have read in this forum - the stock muffler is the real restrictive part of the exhaust system anyway...

So I assume that if I replace it - whether it be with larger pipes or the same size - I should still see some improvement.

Sorry Then I have no idea what size Exhaust you have on.

Good luck All The Things I can Measure are not stock.

Do none of the Auto Parts places Have one in stock for you to measure.

Measure the outside diameter and subtract the wall thickness should get you close.

Good Luck

Hi
on my 1989 v6 cat is 2 1/4 diameter external diameter. will check tomorrow as it has been removed. rest of my system is made up of various diameters. going to build a 2 1/4 system as it seems to best all rounder

Thanks a ton! I look forward to hearing back from you tomorrow...

My stock cat is 2.25", but my stock tail pipe is 2". I'm replacing the cat back with glasspack and going with 2.25 turn down until I can find a shop to quickly and cheaply bend up a replacement 2.25 tailpipe identical to the stock 2". I figure I can save some money doing the welding myself.

Were you ever able to check the size?

Is your truck a V6 or 22re?

V6 (3vze)

Hi
thought i had posted size. mine is 2 1/4 " diameter.