'87 302 E150 van:
I would like to check to see if my catalytic converter is perhaps not flowing well without having to simply pay to replace it right off the bat.
I cannot and will not be punching out the converter's insides. I don't agree with the ethics of this and in any case my location is requiring emissions tests next year which would surely fail it.

So my question here is, is there any way to test this? I could disconnect the Y-pipe but it's going to leave the other side of the exhaust hanging, it might fall off if I try to test this on the highway. And the exhaust temp on that side of the system is really hot at the top and there's a lot that can be damaged from that hot air.

Realistically what is the best way to test a 302? I saw a page which says to pull out the O2 sensor and see if it runs better since the hole would relieve the back pressure. Again this may present a problem with hot gases and the O2 sensor will be offline, confusing the results. Another mention, not for this engine, said "if there is 21 in of vac at idle and 15 in at 4000 rpm, the converter is probably clogged". If the engine's not being loaded I'm not sure how valid this is, nor if it is appropriate for a 302.

 

I belive it can be tested. They (not sure who) drill a hole before and after to get measurments and can tell.

If they go real bad and start to clog, your can see overheating.

 

Hey maybe if I rev it up, measure vac, take out the O2 sensor (hot hot hot!) and measure against that, the difference would be apparent. I should even be able to do that without a warmup. But I don't have a tach so I'd just have to ear the rpm.

Can a converter be put in without welding? My muffler was patched in with exhaust clamps and nobody has ever said anything at inspections even by the hardass who failed me for a pinhole in a muffler weld. So can I assume it would be legal to cut the cat out and attach it with the same exhaust pipe clamps?

 

I saw underneath where there is one box, the air pump injector tube, and another box. This is before the obvious muffler. Are these both cats? What's the difference?

 

I did take the advice of that first site and pull the O2 sensor out of its socket, left it plugged in but tucked out of the way.

IMHO there is more power, but it's hard to say objectively. It was louder and that always makes things SEEM more powerful.

I should take it out on the highway and see if the top speed is better, that's when there's the most flow through the exhaust. I would need to do some shielding though, the gas coming out of there almost melted the O2 sensor harness even though it was not in directly front of it. Probably a bit of reflective aluminum foil tape will shield it. The starter motor is near here too but not much else.

I'm just not sure. Certainly bypassing a good cat would improve the performance some, so does improvement mean the cat should be replaced or not?

 

I put the same question on this forum a couple of months ago, and added some drawings to make it all clear.
Look here:
https://www.ford-trucks.com/forums/s...d.php?t=352213
I was assured, that both items are cat's. Also, that aftermarket replacements often consisted of a single cat.
Inspection will show that the two items are one welded assembly.
Cor

 

Why on earth do they have 2?
This really suggests it may be creating a flow restriction that would lower power and efficiency over just 1.

I do see where some aftermarkets can be put in with exhaust clamps. I should be able to cut them out OK, but of course if only one is going back in I'd need a significant piece of pipe to take up the place of the one which is not there.

This is related to the air pump, isn't it? The first cat is straight off the manifold, then we inject air with the air pump, and then try to catalyze the exhaust again with the additional air? If so I'm not sure if one cat could do this job. Since we have emissions tests starting up here monkeying with the system could be scary. I have almost a whole yr before my date comes up, though.

 

Danny, be carefull as you will need a new y-pipe as well.. The way those cats are hoked up is there are 2 seperate pipes, one for each side of the engine, they BOTH go into the first cat, then it's a single outlet cat. So if you are going to replace it it's best to have an exhaust shop do it so that they can make a new y-pipe.

 

Right, that's a good point!
I noticed some of the aftermarkets included the exhaust pipes around the converter itself. There would be an obvious need for this since as you point out the 2-in cat can't be easily replaced.

 

The first one is the smaller one of the 2 but more importantly, it also functions as the Y-piece, joining the two downpipes from each manifold, so you should retain this one, even if 'emptied'.

Check with the aftermarket suppliers such as Walker, and see what they would fit/supply.
Perhaps one cat is enough, and that one could be fitted in place of the second one (first cat emptied, or rammed through). Cut after the AIR injection and all should be well, I like to think.
Cor

Edit: I see that pfogle was just ahead of me.......

 

Yeah, I was just thinking about ramming out that first cat. I'm not sure how easy this would be to do without taking it out, even if I was able to get enough leverage to smash it up wouldn't I need stand it up so the debris could be shaken out?

Of course this would definitely be a point of no return, so I'm not going to cross that without knowing a lot more about that system and if it's bad.

 

If you use a 3 stage cat, you can safely ram a pipe through the first one. MAke sure you're new one has provision for the AIR system. It will help extend the life of it.

 

So I put aluminum tape over the O2 sensor harness and took it to the highway with the O2 sensor hole open. The sensor itself is still attached so I think the comp will just read it as cold and generally run the same.

I got the impression that it's faster off the line, and call me crazy but I think that while letting off the accelerator it coasted a LOT further. But once it switches to 3rd gear (3 spd non-OD) on the highway I didn't seem to go any faster. Up a very gradual rise in the highway it basically topped out at around 65 mph. Down the same hill, I did see 75 and it was still accelerating but only slightly (there was a bit of traffic). Hmm, I think it was better but not night-and-day kind of difference. I think that demonstrates the system is not bad-bad but can't rule out being possible to improve it.

I don't know. The flow from a new cat might have more flow gains than opening that 3/4" hole. Or maybe not even that much. Or maybe the aftermarkets are crap (it certainly happens) and make it worse? I still get the idea that 2 cats are probably not a good thing and a modern one would flow better. Unless modern regulation makes current ones even worse for flow, also possible I suppose.

 

You can get high flow cats. It sounds more to me like you have some other issues.. How does it run? Is it strong, or is it a dog off the line? Does it idle smooth or rough? When was the last major tune up?

 

It's not all that bad off the line but lacks highway performance. It has always been a dog and a gas guzzler for the 5 yrs or so I've had it though it got a whole lot better when I found the problem with the stretched timing chain. Idle's not bad.

There's no one "tune up" here, but it's had new O2 sensor, throttle sensor, timing is set of course, etc over the years. Fuel pressure is ok, at least at idle. Performance is still lacking. The valves are quite inaccessible in the EFI van and I've never messed with them. I know the intake manifold leaks but it's a MAP system, not MAF, so it's unlikely to change the mixture. I'd like to test the pressure and temp senders but have no info on them.

There's no decrease in performance, if there's something here it would be a problem that was there when I got it.