I've been wanting to fix up the exhaust on the car since I got it. I'd like it to flow better and sound better. One of the guys who had it before me slapped a side-pipe together off the stock Y-pipe with a glasspack. It hangs too low, leaks and is pretty loud. I'd love to go dual exhaust, but it's looking like a bit of an issue. From what I gather so far, I'd need a new transmission crossmember since there's only one indentation for an exhaust pipe stock and I'd have to put some new exhaust mounts in. From there it's just measuring out the pipes. It would be nice to be able to do this at home, but given that I don't know how to weld I'm thinking my best bet for dual would be to at least replace that crossmember and go to an exhaust shop with as many parts as I can. Alternatively, I could get rid of what's already there and go single all the way back from the Y-pipe. If I can do a bit of a repair job on the current exhaust and do something more worthwhile with the money I could live with that also, since I doubt a new exhaust is going to net me much power from the smogged engine either way. Anyways, I'd like to hear your guys' takes on this, since this is the first time I'm really digging into custom exhausts and the likes. Thanks!
Totally illegal. Any exhaust shop is risking a $10,000 fine for not installing a single catalytic converter in the original location. They can install a "dual" exhaust, AFTER the catalyst. This is FEDERAL law, so it doesn't matter that your location doesn't do emissions testing. The good news is that modern monolithic cats flow much better than the pellet-style cat the car came with.
Well I guess that's that then lol. Just have to fix up what I've got then because that's probably about as good as it'll get. Luckily (in this case at least) out here vehicle inspections are basically non existent. Thanks for the reply
Doesn't mean you can't use a larger, smoother "Y" pipe into a large-diameter catalyst, and large diameter, mandrel-bent tubing out of the catalyst to the muffler and then to the rear of the vehicle. Most "exhaust shops" will crush-bend the tubing. You don't want that. No, I don't expect there will be any ready-to-assemble "kits" for a Riv. Not being able to weld is not a particular problem. God bless stainless steel (NOT aluminized mild steel) band clamps. They're made in several styles; there's the straight kind for butting two pieces of tubing together, there's the stepped kind for an overlapping (Lap) joint where one pipe slides into another. The ones I use have two bolts. There's shorter, one-bolt band clamps that I haven't tried. For example: https://www.summitracing.com/parts/sum-681250 And again, you want the stainless steel ones. I bought mild steel by mistake once; they lasted several years but eventually rusted out.
Most shops around here have no issue doing new exhaust with no cats, I’ve done 10 or more vehicles without cars and never had an issue.
Much easier going with a good flowing single with a high flow cat. As Schurkey mentioned, the old pellet type convertors were horrible, that style convertor alone is the biggest restriction to flow, not the lack of dual pipes. If your '75 455 is stock (205 hp) duals wont help anyway.
If the pellet converter were to fall off at some point, have your Riv towed to a shop for a complete new exhaust. The routing, bends and hangers (everything other than the crossmember) for a ‘71 are likely correct for a ‘76. Are you sure about the year? Maybe it’s a ‘71... (I think shops are a lot hinkier about removing a cat they can see than welding on a car that doesn’t have one). Ask around for references. Ask the guys with clean ‘80s cars who did their exhaust (El Camino people maybe-they have crossmember issues and need talented, cooperative shops for them.) A good ‘crush bent’ job with duals and no cat would be a step up on a stock smog 455, or ask for advice on here what kind of bits and pieces from other mandrel bent kits (2 1/2”) will work. A kit plus straight sections to extend the headpipes and tailpipes may be the ticket. There’s likely a guy near you who can do exactly what you want-he just doesn’t advertise it. Patrick
I would think finding a crossmember from an earlier Riviera would't be extremely difficult and would offer the easiest and least costly solution.
Don't know where the OP is exactly from, but in Quebec what reallt matters is the actual noise that your car makes. Some cars appear to be cops magnets just because of the heavy sound they make. If they find your car being too noisy you'll have 48 hours to get it inspected in a designated car garage. This shop will decide if your car is legal or not. If your car is declared unconform you'll have to make modifications to make it legal, else if the cops catch you again you are in for a fine
Yes Canada has the same rules as the US, most of us typically cut off the old cat system and bring the car in without any exhaust and then have them do their thing. I’ve never had any shops give me a hard time about not adding a cat to the system. It’s removing the cat that some shops won’t do. You may be able to do a dual 2.25 down the one side? That or a single 2.5 with a magnaflow muffler.
Cops and the MTO (ministry of transportation) up here don't really bother guys for exhausts unless it's those super loud and annoying fartcan import cars.
The only time the MTO really goes out with the DB reader is when someone complains about the kids riding around on their 2 stroke dirt bikes and even then most of the officers ride themselves soooo lol
Be interesting to find the Db limits so you have a defense. I have a Db meter for a long time now. I use it to set up my home theater system. I'll have to see what the GS registers at. My GS is relatively quiet at idle and cruise, but it really screams at higher throttle openings.
I'll give a shop I've been to before a call and see what they can do. The stock cat is long gone luckily so shouldn't be an issue there. Currently it looks like its a single 2.5 down the side that goes through a glasspack and that's it.
That's what I was wondering too. I know that the engine's been warmed over a bit, but I'm also considering if I should hold on the exhaust until it's actually a bottleneck. My guess is without the stock cat it won't be that much of a problem for a while.
Please Note: Sean is in Canada, so US Federal law does not apply. Still depending on your state, I agree that enforcement if this is virtually nil, and many shops will reconfigure your exhaust.
Where I live they've started putting up readers downtown that work similar to photo radar, so if they think you're too loud they'll send you a ticket. Most likely aimed at the kids who chop the mufflers off their Civics, but I haven't heard much about how sensitive they are. Other than that, it's pretty rare out here for guys to get tickets for their loud exhaust, at least from what I hear living next to a main road lol.
