eric_daniel

Does anyone know if it is legal in texas to take an 85, which has a y pipe from motor to one cat converter and a y pipe from cat to two mufflers, and install a second cat converter and have true dual exhaust? I've heard that things involving the exhaust are very "iffy." Or does it just have to pass the emission tests? Just curious I figure this would probably free up a few more horses fairly cheaply. I already have the Flowmaster mufflers.

dwestsr

I believe the emissions rules are Federal and apply to all states that currently require emissions inspection. Technically speaking, If it did not come with dual exhaust , you cannot put them on. However, it depends on how strict your inspector is. I expect that it will pass the test, but If your inspector wants to go strickly by the book, they can fail the car. It's a bit like replacing the precats with a straight pipe but leaving the main cat. It will likely pass but if you inspector is sharp, they will know that the car came with the precats and can fail the car even though it passes the emission test. As I said all this is technically speaking. It's a gamble. :cheers:

eric_daniel

Thanks for the info. Thats weird that they would have federal regulations. I thought that California had stricter regulations and my home state of Louisiana doesn't even have emissions regulations. (not saying that won't change!!!)

rhneff

Eric,
dwestsr is correct, Texas tests to Federal emissions requirements and technically doing what you suggest is not legal. Realistically, I've never had anyone including the dealer go under the car for a pre-OBDII vehicle inspection (ie. prior to 1996) - what they do is hook up the sniffer, run the engine and if it passes it passes. So the real risk is that it may not pass - you might want to have it tested in current configuration to see how the engine tests and how much "margin" you have before deciding to proceed.

Frizlefrak

Eric....I don't know how strict Ft. Worth is, but in El Paso they just shove the sniffer up the tailpipe, do a cursory glance to make sure everything APPEARS to be intact, and slap a new sticker on the windshield. Next time you have a friend who is gonna get his car smogged, go with him and see how thorough the facility is. If they are somewhat lax on visual inspection, you know where to take the Vette once it's breathing through both pipes as it should have been have Chevy not taken the cheap route. As long as the exhaust vents through a catalyst, your actual emissions shouldn't change.

65Z01

While emissions standards are set at the Federal level, any component that has an EO number can be installed, even in front of the cat(s).

For example ealry L98s had two pre-cats in the front Y followed by a single main cat. Replacing the front Y with a pre-catless one and a 3-stage main cat is 49-state legal.

I don't know of any true dual systems on the market that come with an EO number nor even of any FL headers that yet comply with emissions certification.

However, I'm sure if you use two hi-flow main cats in a true dual system on a well tuned L98 it will easily pass the sniffer. You won't gain much over a good hi-flow Y-pipe system with a nearly stock motor; but upgrading your stock exhaust system to hi-flow will yield good gains.

A rule of thumb is that you need 2.2cfm of flow for 1 chp of power; so a 300chp SBC needs 660cfm of exhaust flow. A 2 1/2" pipe will flow about 560cfm and a 3" pipe about 800cfm. With these numbers you can size the pipes, cat and mufflers for best results. And remember the pipes need to be mandrel bent so as to not reduce effective flow diameter.

redfast

Do it. And then make friends (in high places i.e. inspection garage) :yesnod:
:lol: I still did it - loud/worth it. Mine wouldn't pass, then I made another friend. :thumbs: Do it !!