It was a suggestion thats why i prefaced it by telling you I wasn't busting your *****. But your perception is entirely your own.

Weld everything from the collector back and use the clamps behind the H so it came be removed. lose the stub pieces behind the converter and slide the H directly into the converter. You'd have two clamps and the ease of removing it, and what you have in the fancy clamps probably would have paid for most of the welding.

 

Thats the joy or pain in this hobby, you start making changes and suddenly you're down a rabbit hole based on what you did to the car 10 years ago. And you would definitely have done a few things differently had you known where you would end up.

I wasn't exaggerating, i was counting the u-bolts on either side of the converters. Thats ten clamps. I would weld everything from the collectors back and only leave the two clamps behind the H so you could remove it.

 

remember you questioned the Y pipe on my sons Mazda…saying it was too small?

don’t get upset when someone critiques that mess under your car. it is a mess.

 

I hear you. Similar for me 2 of the 3 local tracks have closed. And of course the slowest of the three is the lone survivor. But at least its not the furthest.

😭 my performance range but at least my car was 50 years older...

This pic is from 1/8 mile Old timers day at Etown in the heart of the summer. She ran 6 passes and IIRC 10.4 every single time, but won 5 of 6 races because she was up against similar stock competition. And my 69 obviously runs well for what she is.



continued

 

For sure. She's as quick as stock W31s.

Car and Driver, May 2017. 2017 Dodge Challenger GT AWD 305 HP V6.

Curb weight: 4103 lb

C/D TEST RESULTS
Zero to 60 mph: 6.3 sec
Zero to 100 mph: 16.3 sec
Zero to 130 mph: 35.4 sec
Rolling start, 5-60 mph: 6.7 sec
Top gear, 30-50 mph: 3.5 sec
Top gear, 50-70 mph: 5.1 sec
Standing Ľ-mile: 14.8 sec @ 95 mph
https://www.caranddriver.com/reviews...d-test-review/

That's an 8.8 in the 1/8 mile when run through a calculator.

If tracks become obsolete we can test 30-50 mph with an app to gauge improvements. There is a library of road tests from similar combos with more and less power that can tell the story without actual track passes. But of course a chunk of the fun in making an actual pass is gone.

Assuming Car and Drivers Challenger ran at a 4303 lb test weight she showed 288 flywheel hp out of 305 possible hp.

 

👍

Great gain.

Many ways to skin a cat .... Do what works for you.

 

Gang
Just to chime in for the big car guys. I don't think too many of us B & C body people count tenths. But more power to you all who do.

I added an H pipe to my 98 (yeah...) in the 1980's and did same to my '66 Starfire in the late 90's. Oddly enough the 98 has a slightly rowdier cam and the Starfire is subtle. But both sound about right with the H pipe in.

My experience is both cars got smoother, quieter and, just maybe, a tick more power from the crossover. I'm no scientist, but have been very happy with the H pipe crossover for decades. The exhaust sounds are consistent and smooth like I like Olds 455's to be in big cars.

I believe the warnings about tougher servicing are on point. But then I haven't had to do any in 20 or 30 years with the way I use my cars.

In the end, I wind up in my usual place: to each his (or her!) own. Enjoy the cars, make 'em your own as you see fit and live with your choices. Then change course, if warranted.

Cheers
Chris

 

Thanks 66_Jetstar for mating the cat directly to the H pipe idea. Only been getting maybe 4 hours sleep for the last couple weeks, everything twists me the wrong way, even helpful criticism. Despite severe siadic nerve pain, really will pay for this. It is kind of like being set on fire, screaming pain, literally, not much fun at all. Anyway, I took another look at the exhaust. I disconnected the H pipe and removed the short piece in-between the two. Hammering that piece out with vice grips attached and noticed chunks falling out of the converter. I pulled converter after shining a light and seeing more dark chunks behind the screen. Even with that chunk out of the converter off, I could barely see a bright LED light through the converter. So I beat all the chunks out, now hollow. Without a doubt, it was killing power. I used a 304 Stainless 2.5" ID adapter, just long enough to fill the space. Will have to see how it sounds when I take it to my Daughter's place to be welded. It is a half hour drive, won't be happening for two more months or when the roads are dry. Hoping it won't be too loud, those cats definitely were absorbing sound too, not just power. With the H pipe moved up, it just clears the huge 4L80E pan, perfect. Since it does, there will be no clamps between the header collector till the mufflers, all will be welded, if it sounds good.

 

Another thought----since you are in the midst of redesigning your exhaust and will be getting the system welded....why leave non-functioning cats on there at all? Remove the cats and substitute straight pipe and make it much cleaner and streamlined. You will get more clearance around your trans pan and etc.

 

holy crap…maybe those plugged cats were the reason you couldn’t get your EFI to work properly?

do you even know if the cats were working or how to check if they are?

 

Definitely didn't help, maybe they went bad, right away? It would explain why it would act goofy with the carb too but only every now and then for some reason. I am adding a fuel pressure gauge thought it might be too much pressure from the mechanical pump, causing the issues. How do you check catalytic converters short of an exhaust analyzer? A vacuum gauge? FYI the cats were bought in June 2022 and don't have many miles on them. I had an AEM wideband on the car around the same time and not many miles, talking a few thousand at most on those cats. Apparently the cheapest cats on Amazon weren't the best to buy.

 

That I might do, driver side is pretty close to the trans wiring and shift cable. Or I could buy decent catalytic converters to replace them. But straight pipes won't plug. These cats had O2 sensors built in. I need an O2 welded in as well. It would clean up the exhaust. Pretty sure I have a stainless weld in bung on hand. I will measure and hopefully something like the pic below will work. I would leave the passenger gutted cat until a bung can be welded in for my wideband. I need it for the new Edelbrock heads and roller cam. It would cut out two more clamps per side for now as well. Will measure to see if these will work.

 

when running, the outlet temp of the converter should be about 100 deg F hotter than the inlet

 

Yes, that makes sense. I do have two more of these converters around. I noticed these are no longer available on Amazon and someone had a failure at a month old. The other ones only had a few miles on them too. I will inspect them and the other side as well. It may have been just one bad converter. If the other one is good, I may swap one and periodically check with a temp gun, love the less exhaust stink. Decisions to make.

 

So I pulled the other side, the converter is fine. Also pulled the other converter off my other exhaust system, also fine. So I am putting on the extra working converter for now in place of the hollowed out one. I will order those two pipes, which are the perfect length and weld in an O2 bung in one, which happen to have on my shelf. I will checking temp after I get it running again to make sure they are functioning properly.

 

I've never heard of cats "plugging up" (these days). Failure for a cat is either emissions compliance or physical breaking of the honeycomb 'brick' inside. As long as your exhaust temps are in the proper range, they should work (at least with some level of efficiency). If you remove them, you should be able to see through the honeycomb when held up to the light. If you run leaded fuel through them, you'll affect the chemical reaction of the precious metals at the surface and they'll no longer function but they shouldn't plug up. Of course, these are aftermarket so God only knows what is inside.
Not sure what the feedback loop is/was for your EFI system and how the cat efficiency could have affected the set-up. Was it taking a reading from your O2 sensor(s)? If so, could be your sensors are bad and not the cats. That's pretty common.

 

This might be the first picture I've seen of your car on the ground Looks good!

 

I can see through both these cats, a hex light spot, same on both. It was a Holley Terminator X Max on a converted Performer RPM for SEFI with timing control and the in tank high output module with a steady 62 to 63 psi. I had very different readings between the AEM and the Holley but they read off different sensors. The EFI was finally getting where it was running decent then it acted funny and the Terminator X Max died all together. I should have sent it in right away for warranty. Honestly the only way I would reuse it is in a 88 to 98 Chev/GMC 1/2 or 3/4 4x4 converted to Olds V8 power, just need a crank for my 403. I am staying Qjet, which is spot on, according to same sensor that came with the Terminator. I have a brand new O2 sensor I may use.

 

Ordered the exhaust parts. Anyone with a nice dual exhaust system, 66_Jetstar included, post pics of your stainless exhaust systems for inspiration. It will be a couple of months. I actually want seat of the pants with the new Edelbrock heads and roller cam. It will also tell me how much these cats restrict flow, my guess is a noticeable amount. See you in a couple of months.

 

You probably know this already, but most factory set-ups use an O2 sensor before and after the cat. That allows monitoring of the health of the converter. I'm definitely not suggesting you go this route - the quick/easy temp check mentioned above should work for what you want to do.

 

I just want a more apples to apples comparison before I ditch the cats with the new Edelbrock heads and roller cam. By the amount of light coming through cats, it has to be a restriction. Yes, dual sensors have been around for decades to make sure the catalyst is functioning properly. Only parts stainless are the the chrome Spectre 3" to 2.5" collectors currently on the car and the tail pipes. Plan is new stainless 3" collectors to 2 3/4"OD to 2.5" ID and OD to the H pipe, all welded in. It will be a couple of months before it gets done. Honestly if noticeable power is on the table, which it is, the cats can go. My garage door stays open for 10 minutes to air out before automatically closing. Enough to get rid of the exhaust stink.