I know a lot of folks here are not running cats. I'm still not completely sure I'll run them myself. If I do, however, how picky is position of the cat?

The factory mounted the cat so it could drain completely(pic #1). I'm proposing mounting the cat in a more horizontal position where it won't completely drain(pic #2). I'm concerned it will accumulate soot and condensation in this position(pic #3).

Is this a valid concern? Does the cat have to be positioned so it can "drain"?

 

In many cases, cats are mounted horizontally so there is little or no "drainage" other than the exhaust flowing through the cat.

The cats are mount close as possible to the exhaust manifolds to help them heat up quickly to start scrubbing the exhaust.

 

You're saying that manufacturers have installed cats with a "pocket" like shown in pic #2 and #3? If so, that would ease my mind considerably! Mine would fit a lot better if I could angle them up from the factory position.

 

There is no need for drainage. As they heat up, any condensation cooks out. My 04 Tahoe has the left converter angled and the right one horizontal. I don't know where you get that they need to "drain".

 

It's not as much condensation I was worried about, as much as soot and particulate matter. I really wasn't sure that was even an issue. I just thought I'd check before assuming I can mount the cat like I want it.

To be clear where I'm coming from, I have very little first-hand experience with this stuff. I look at things more theoretically, and depend on folks like you who have experience, to correct my mistaken theories.

Thanks for the response!

 

All particulates and soot blow through and out the pipe. Converters have been around for 45 years now. Not much new with those anymore. Be more observant and look at more cars and trucks.

 

Google is your friend. There are many images easily found that show horizontal placement.

 

Are you running them because it has to pass a visual inspection or to help with emissions? My factory '97 S-10 4.3 cat is horizontal under the truck.

 

I suggest running them on a 4th gen with headers to reduce drone.

 

I'm installing 2010 components in a '87 truck, and as much as possible, I want it built like a GM engineer would have done it.

It definitely needs to pass a visual inspection, since the '87 was originally equipped with cats. It doesn't feel quite right to just gut the cats. Besides, I've got the 2010 stock units sitting here, so it's not going to cost me anything to install functional cats.

If the stock cat placement works out, I'll likely run all four o2 sensors. I'll adjust the tune so the rear sensors don't trigger the "check engine" light. But in the future, if I have reason to question the cat's performance, I can just use a scan tool to read those rear sensors.

 

The rear sensors only come into play if/when the cats don't do their job right. That is their total function. So you can leave them in the tune if you want.