Cats, downpipes, etc...

I have my 3" Hogan DP, but can't remove the stock unit due to ridiculous rusting of the cat studs/nuts. So I stopped by the exhaust shop that worked on my 68 system, to see if he could help me with this job. Told him I'm also considering a hi-flo cat at the same time, and he is checking on a price for one for me. However, I'm sure I can get the best deal buying it from Hogan?? Or elsewhere? Anyways... do all the aftermarket cats have NO O2 sensor bung? Looking at the Magnaflows on Hogan's site, it appears the O2 simulator is needed with their cats. Is that correct? Cat price is great, $55, $40 for the O2 sim. Also, which cat do I need for this? (size-wise). www.hoganperformance.com/converters.htm It looks like I'll need the 3x3 Magnoflow cat, but how does that work with our exhaust? behind the stock cat is not 3"...

Also, I see my stock DP is in contact with the front sway bar. Is that normal? Seems to me there ought to be SOME clearance.

Anyways, just looking for input on which way to go with a new cat, any comments appreciated.

Or can I only use the Hogan 3" DP, which has a 4b flange at the bottom, with a STOCK converter? I don't really feel a need to eliminate my cat, but a higher flow unit would be nice, if one can bolt up to the new DP.

I see NAPA lists direct-fit 2.5" cats with the 4b flange on them, for $204. It appears our stock cats have a slip-fit into the resonator? Seems weird... no clamp or nuthin.

I would think that since most performance cats can work in many different exhaust systems, they won't include an O2 mount, since certain cars will have unique designs. Just my hunch, I might be wrong.

If the cat recommends a simulator, it won't help you pass inspection, so why not just use straight pipe? Lol, a piece of 3" diameter stainless race pipe is $50 from INTENSE, so for the prices you listed on those cats, I wonder what you're getting? If you buy a high-flow cat, I'd go 3" to 3", then use a tapered reducer to mate up with the stock 2.5" pipe. I had one of these, but sold it to olds105.

Was your car lifted up when you saw the pipe making contact with the sway bar? I noticed the same thing once, then lowered the car and the bar moved a good 2 inches away.

Yeah, I had it jacked up last night to change to RP oil, and noticed the contact. I'll check again with it on the ground.

Magnaflow does list some cats that include the O2 bung, but no direct fit cats for our Rivs, only Universal style cats. I don't really want to eliminate the cat, and I can get a hi-flow direct fit cat from the shop, kind of spendy though, about $200. He said it's not a Magnaflow, didn't catch the mfgr name though. Probably the same one NAPA lists as a direct fit for about the same $. The only direct fit hi-flo cats I can find are all 2.5", nothing in 3" that is a DF. Don't know, I might just have him do the DP only, and put new bolts in the stock cat's flange.

Aaron, if I were to unbolt the stock DP up at the manifold, how hard do you think it'd be to separate the cat from the resonator? Then I could pick up the NAPA direct-fit cat, and install that and the DP myself...

Hogan now tells me he has a bolt-in cat that goes with his DP, but it will have to be welded on the back end. $125, or add $75 for True OBDII.

The converter for your application is our CC1 125.00 which will bolt up to our downpipe, has the O2 bung in the outlet pipe and attaches to the factory cat back but must be welded. We are now offering this item with a True OBDII cat for an additional 75.00. This cat has more substrate and an additional precious metal to assure no P0420 code that sets the SES light.

I really don't know, Dave. I didn't separate the DP, cat, and rear manifold when I removed them. I just took them all off at once. The mani bolts came off fairly easy, though.

If you pull them all off together as I did, I'd think you'd have a better shot with all of them off the car. You'll be cutting the pipe between the cat and res to do this.

If all else fails, you could ask Ed Morad for a new (used) rear manifold. Probably wouldn't be much $.

What I'm wondering is what's the diff between Hogans cat with O2 bung installed, and his "TRUE OBDII Cat", for $75 more. Can't we just plug into the O2 bung and it's good to go? (I emailed him on this)

I'm really leaning to buying this from Hogan, and just cutting the stock cat out. Shouldn't be any problem to unbolt the stock DP at the top, the studs/nuts look nice and clean up there. I have no plans to pull the rear manifold at this time.

Well I took the easy way out with the DP/cat install. Hard to beat 1 hr and $60, including installing a new front O2 also. I disconnected the battery after getting it home later this afternoon to reset the PCM, so I really haven't driven a lot yet, no seat of the pants diff to report yet. Gonna do some varying driving Fri/Sat and thinking about hitting the Street Legal drags on Sunday. I'll hook up the scanner first though, and see if my KR has gone away... let's see, added front PEM, 3" DP and Magnaflow hi-flow cat. Should see SOME improvement.

PEM?

Ported Exhaust Manifold

Is that the same thing as plog/tog (I may be imagining one of those terms?)

How much do PEM's usually run and how much power do they make?

Jack a PEM is just your stock little cast iron exhaust manifold, except it's been ported out at the openings to allow some air to actually flow out of the heads... I ported mine myself, going by some threads with pics on the various 3800 boards. From the factory, there is a ridiculous amount of restriction from the poor castings. Porting them out does help exhaust flow, though the restriction then is the main body of the manifold, which is still pretty small.

The next step up would be the Plog, or Powerlog from ZZP. It is similar in design to the stock manifold, but with much greater diameter pipes and body. Significant improvement in air flow. I may do a Plog next year, but didn't want to spend on one this summer, plus the cost of having it coated for durability. A PEM is free if you do your own manifold, and have access to a die grinder and bits. Or you can buy an extra manifold for pretty cheap too, port it out, and then swap with your current manifold. I think I spent $30 for an extra one, and I had access to the needed tools at work. A Plog is around $100 or so, but that is just a painted one, the paint won't hold up and the Plog will rust out.

A TOG is an actual header, don't know if they are in current production or not. SLP is a popular header supplier, Pacesetter also.

A "P-Log", or Power Log, is a fabricated replacement for the front exhaust manifold. It uses lighter, larger diameter pipe to improve the flow performance of the front OEM manifold. The OEM rear manifold is designed more like a header; it flows directly into the exhaust, so the idea of the Power Log is to make the front manifold perform equally well.

TOG is short for "The Other Guys", and refers to aftermarket headers.

PEMs vary in price, depending on how extensive the porting and polishing. Many take off their stock manis and port them themselves. Again, the front manifold is the bigger concern, because it's a more restrictive design.

Aaron, aren't TOG's made by a specific company? Maybe I'm misreading, but it sounds like you're saying it is just a generic term.

Yes, the company is called "The Other Guys". They were one of the aftermarket header manufacturers, but don't think they're in business any more.

I didn't mean it that way, but I do think TOG often gets used as a generic term... when referring to headers for the 3800.

Thanks for clearing up the pem/plog/tog issue. I'm glad to hear I wasn't imagining terms.

Is a dremel adequate to port a mani? It may be too lightweight for cast iron.

Jack the R wrote:

Thanks for clearing up the pem/plog/tog issue. I'm glad to hear I wasn't imagining terms.

Is a dremel adequate to port a mani? It may be too lightweight for cast iron.

I used a pneumatic die grinder at the shop. It is a lot of work, but a good Dremel should do it, I would think. I just looked at some Dremels at Home Depot, but they seemed a bit lightweight to me.

1998 Riv wrote:

race cars were just too loud for my 2yr old's ears...

My hearings gone to crap because of my dad having me shooting without hearing protection when I was young. Don't screw your kids' hearing up.

When I take him again some time, we'll have ear plugs or something else for him. I also have moderate hearing issues, due to heavy equip operations growing up in rural America...

Thanks Aaron!