My '92 F150 5.8 has been running increasingly sluggish, even for a 351. Slow acceleration, won't rev above about 3800 RPM's, and even less power than usual. I put a vacuum gage on it today, and it confirmed my suspicions. Only about 16 in Hg at idle, not much over 20 in Hg at 2500. So, I pulled the O2 sensor out and checked again; a shade over 20 in Hg at idle, and mid 20's at 2500. I took it out for a spin, and my butt dyno confirmed the gage readings; plugged exhaust.

Upon looking under the truck, it's obvious that the exhaust has been replaced at some point from the second cat rearward. All the joints are welded instead of clamped. Also, my factory service manual indicates that my 5.8 should have a dual-outlet muffler with two tail pipes exiting behind the RH wheel. Mine has a single tail pipe like a 5.0. Since I can't unclamp and disconnect the muffler from the two converters, I'm probably just going to replace everything. I'm not real happy with the previous exhaust work anyway.

So, my questions are this:

1) My truck has dual in-line cats. Does the replacement system also need to have two cats, or is a single sufficient? I have found systems on line from various parts stores which show the head pipe/single cat replacement.

2) Since I'm going to replace everything, what is a good (and inexpensive) split dual tail pipe and muffler set-up? I want it to sound a little louder than stock, but not much. I really don't want it to sound much louder in the cab, but have a nice tone outside.

I plan to do all the R&R myself, so bolt-on options (okay with light fitting) are best for me. I'd like to get things ordered this week, so your feedback is greatly appreciated.

Cheers!

JD

 

If you don't have to pass a sniff test, just gut the first cat, throw the second away and go from there. And yes, if you have to have a cat, using only one will be fine.

 

I was just looking at a complete dual exhaust system for my 93 F-250 5.8 setup starting right after the cats to tailpipes from RockAuto.com, complete setups range from $265ish to $311 depending on whether you want the tailpipes to exit on the side of the truck or the more expensive kit which exits out of the rear. Both kits offer your choice of mufflers (Dynomax or Walker) from stock sound to down right aggressive. Have a look, hope this helps...

 

Unfortunately, I have to pass sniff test for about two more years. In this county, you don't get past the sniff test until 25 model years old. After that, I won't worry about it anymore.

And so what you're saying is the parts-store set ups that show the head pipe and single cat will fit/pass. That simplifies things greatly.

Thanks!

JD

 

That sounds good. I'll take a look on Rockauto. My preference is to have the tips exit on either side of the truck; one in the stock location, and one opposite that position. I'll look and see if that's an option or not. One thing I don't want to do is have to delete the spare tire; I've seen some options that require that. Thanks for the tip!

JD

 

Oh, one other question. If I go with the head pipe with single cat option, do I need to connect the air pump plumbing? I'm assuming that the pipe assembly doesn't come with the air pump pipe. From the photos on the web site, it appears that the cat for the replacement system is in a different location from stock. If it's easy to connect, I'll just go that route. But, I'm not opposed to removing the air pump and all it's plumbing. It would simplify and tidy things up under the hood, and if I don't need it to pass the state inspection, then off it comes.

Thanks,

JD

 

I'm not sure. If you have to pass a sniff, they may look for missing parts also. The air pump only sends fresh air to the cat on start-up. When it warms up it does nothing. Go ask someone at a DIFFERENT inspection station than you plan on using and see what they think. Post the results. Maybe someone here knows................

 

If you have to pass a visual test as well as a sniffer then you need to keep the AIR injection system hooked up. If not, then you can remove it.

Most of the aftermarket systems I have investigated do have a fitting for the AIR injection pipe. They typically include some silicone tubing and clamps.

 

There you go. Keep it, for now.

 

That's a good idea; I'll ask a random inspection station tomorrow, and post what I find out.

JD

 

If the replacement comes as you say, then hooking it up is not a problem. Since mine is all metal now, I assumed that the replacement would need to be also. If it can be connected with just a piece of silicone hose then it'll be easy. Thanks for the input!

JD

 

I looked at the kits on RockAuto, and found the same P/N (Walker 17447) on eBay for $30 less, and free shipping. I ordered the cat-back kit and a head pipe/cat assembly from the same place. Saved quite a few dollars, and it should all be here this Friday. I'll post how it looks when everything arrives.

Thanks,

JD

 

Can't wait to see it as I have to do this too! If you can, post a video or a link to one on youtube, want to hear it rumble!!

 

I got the exhaust system swapped out and buttoned up on Saturday. It took about 3 hours start to finish, and I spent quite a bit of time making sure everything was lined up and fitted so it looked good. The parts I used were:

- CATCO 9650 49-State catalytic converter kit:
This includes the head pipe assembly, catalytic converter, air injection tube kit, and hanger and clamps. The instructions were pretty mickey-mouse, but it's pretty obvious how everthing goes on.

- Dynomax 17447 Super Turbo Cat-back Exhahust System Kit:
Included were the extension pipe (cat to muffler), Super Turbo muffler, twin tail pipes (RH exit), and all hangers, brackets, and clamps. Again, not much for instructions, but pretty simple to figure out.

The above two kits provided everything I needeed to completely replace the exhaust system. One small hicup I encountered was that the outlet pipe on the catalytic converter was the same size as the inlet end of the intermediate pipe. I just took both parts to a handy Midas Muffler, and had them swage the outlet of the catalytic converter to fit over the intermediate pipe. They did this at no charge for me.

I used a pneumatic 3" cut-off wheel to remove the old exhaust system. Someone had welded a new muffler in place at some point in the past, so it all had to be cut off. It was a simple task to get everything off, and luckily, my manifold collector nuts came off with a little heat from a torch. I'd replaced the RH exhaust manifold 2-3 years ago, so that side already had brass nuts. The LH side looked to be original, but they came off without too much trouble anyway.

When I had everything cut off, it became apparent why I had such a severe exhaust blockage. The core of the up-stream catalytic converter had disintegrated, and plugged up the down-stream cat. I dumped several sizeable chunks of core, plus a lof of fines from the down-stream cat.

Hanging the new system was pretty straightforward, and I followed the usual procedure to hang and alightn the system. Everything fit well, and I appreciated that the kits included all the hangers, clamps, etc.

After everyhing was finished up, the test drive was a night-and-day difference. I don't think the truck has ran this good in the five-plus years I've owned it. A host of drivability issues went away with the installation of the new system. I'm in the process of performing a mileage check, but I can already tell it's dramatically improved. I don't have to drive nearly as deep into the pedal, vacuum is way up over where it was, and the throttle response is dramatically improved. If you have any questions, let me know and I'll try to help you out.

Cheers!

JD