1985 F150 4x4 cat question
 

I don't want to ignite any debates about legal or illegal to remove the cat. In our state when the vehicle is 25 yrs or older it never has to go through an emissions check again.
In Jan when our truck is exempt from the emission tests I want to remove the cat to help it breath a bit better as I sure that original cat has a few issues.
I am wondering about this because I have read alot about scanvenging and back pressure and I wonder what affect removing the cat might have in regards to that. We have the 5.8 in the truck and all of the smog stuff was removed by the previous owner.
Not to upset anyone but I am not worried about the CO2 that might result from the removal. I am not in the least eviromentally concerned about the CO2, whales or the trees. Carbon credits be damned!!!!!! Enough soapbox for now.

Stock carb? It's going to run lean and ping if it doesn't already. Put a non-emissions carb like Holley 600 vac sec or Edelbrock on it.

The only thing it ever affects is the egr function on certain setups. Since you have no egr anymore, it's not going to matter much.

On trucks that old, it makes little difference to whether you have a cat or not. In theory a properly tuned engine will benefit from having a cat, but with carbs, they are rarely perfect enough to see any benefit. The older engines don't scavenge well enough to matter one way or the other.

Thank you everybody for the answers. Yuo confirmed what I thought so now I just wait for January. Yee Ha.

Update:
It does not have the stock carb, it has an Edelbrock 600 cfm on a Offy intake with Mallory ignition. Could the cat be the reason (maybe partially plugged?) we get mild pinging under cruise mode? I have played with the timing and the carb setup (rods and jets) until the cows come home to no avail.

Pinging is usually a sign of leaning out. The cat does not cause this. My previous statement aside, why do you want to remove a component that is not plugged, broken or defective. I know you think it restricts your power, but so long as it is working does it rob power? I mean that as a serious question. I have seen properly functioning cats make track cars quicker. Unless yours is broken, why remove it?

WARNING... HUGE soapbox ahead. Avert your eyes and hide the kids.

IMO cats, air pumps and egrs are one of the worst things ever forced on us by the treehuggers. In the 70's and 80's it degraded the performance of our vehicles, started the trend of removing the auto repair from the shade tree mechanic, and brought unwanted goverment intrusion into our lives in the form of emissions testing. I will acknowledge that the engineering has improved in the past 30 odd years to the point where it is not such a problem on the vehicles produced today. That said, for the "classic" or older vehicles it was nothing more than a bandaide on an issue that nobody cared about but the treehuggers and granolas. If these components are vital to producing horsepower then I would expect to see them in F1, Nascar, and Top Fuel but we don't. In the quest to produce horsepower all of these highly funded groups would have installed these items if it would help them win and they don't therefore leading to the conclusion that they don't help. While my vehicle isn't any of these I can't see any valid reason to burden myself with it if the only reason it was installed was to meet emissions requirements and soon they won't matter as the truck won't have to go through emissions ever again.

Ok. Off the sopabox. I hope didn't offend or upset anyone.

> all of the smog stuff was removed by the previous owner.

Then remove the converter because it is just getting clogged anyways, if it isn't already. When you look inside the honeycombs are probably blocked with carbon. I would use the O2 sensor for a 14.7 meter.

You may be right about it being full of carbon. I will know when I take it off. That is a great idea about the O2 but the truck didn't come with O2 sensors from the factory, however I might weld in a bung in the replacement pipe for the cat. That way I can put in a sensor for A/F gauge. Thanks for getting me thinking.