View Full Version : Any hope for CA exhaust?

05-02-04, 01:43 PM
When I bought my car it had true duals, which I know wouldn't pass CA inspection. Since then I've gotten hold of a pair of stock exhaust manifolds, and will (sometime in the next few months) be installing all new exhaust. Doug Thorley Headers (in theory) makes a direct fit CARB legal shorty header for Vettes. Would there be any noticable increase in power or torque going witht he shorty headers? I've heard that as manifolds go, the ram horns are pretty good, so I'm not sure that a shorty header would help much. Also, am I better off performance wise going with a whole kit from a company like Mid America or having one fabricated (not sure that fabricated would pass CA emissions) and for a regular (but not daily) driver would aluminized or stainless be better? What about mufflers? I want something thats relatively quiet at idle and cruising, but turns heads if I decide to stomp on it. If I can't have both worlds, I'd rather comprimise a little on the quiet idle. Then again, I also don't need to set off car alarms when I play. Right now it looks like I'll be doing Thorley Headers, Mid America performance stainless exhaust (y-pipes and high flow cat) and probably MA Monza mufflers. Any thoughts would be helpful.

05-02-04, 01:51 PM
Almost forgot to say what I plan on having for an engine (if that will matter). Between now and registering in CA I plan on rebuilding the engine to the following specs:
AFR 195 heads
Comp Cams 268H cam
Full roller rockers
Weaiand Action Plus Intake
9.3:1 compression
I may in the future go with a Holley 142 supercharger.

This should all be CA smog legal with CARB EO's.
Hope the extra info helps.

05-03-04, 10:03 PM
Hi Bob

Welcome to CA. The smog situation depends on where in CA you are moving. We have 2 different smog checks, up north where I live we have the easier one. I have a modified exhaust and donít have any problem. It was fabricated locally and as long as the cat and all fittings are still there it is OK. You will need the smog pump and other smog equipment on the car. They are fairly strict on having original equipment but you can get OKed with some modifications by going to a smog judge. I donít know how it goes down south but I do know they must do the check on a dyno with the car at different speeds. I would be careful when rebuilding your engine and keep all this in mind. Some people have 2 engines, one goes in every other year for the smog check, and then they pull it out and save it for next time. You are looking at a smog check when you get here, one in 2 years and then I think your car will be old enough by the time the 3rd one comes along so you wonít have to worry about it again.

Hope this helps


05-03-04, 10:13 PM
I don't know from experience, but I've read on this forum that the ram head mainfolds are pretty good and the "shorties" are better but not by that much.

05-03-04, 11:36 PM
I donít know how it goes down south but I do know they must do the check on a dyno with the car at different speeds. I would be careful when rebuilding your engine and keep all this in mind.
Don't suppose I get a free copy of the dyno results with that do I :confused All the parts I have selected are CARB approved so hopefully the combination will be tunable to support CA standards. I'm guessing that the San Diego area has the more strict inspections.

05-04-04, 11:07 PM
Hello all,

C.A.R.B. approved components are certified to be stock equivalent. Therefore, if all of the components that you are using are CARB, you should be able to pass as long as the engine is in a proper state of tune, I.E. timing set to factory specs, etc.

There are currently no headers that will be allowed in San Diego county on your year Vette. The problem is the EFE that sits on the right hand side of the engine and controls the heat riser in the right hand exhaust pipe. There is no way to adapt that system to headers and the car will not pass the visual part of the inspection without the EFE installed. On the plus side of that though is that the original manifolds flow fairly well . . . but they sure don't sound as nice!!

The best news? You've only got four more years before it becomes exempt from testing. My '75 is enjoying it's first year of exemption :D .

I did a fairly extensive write up a couple of years ago on California smog law on this forum. Try doing a search for it if you'd like. You might find some useful tips.

Oh and by the way, California has been talking about rescending the exemptions for older vehicles. So if anyone out here decides to modify beyond legal limits on their older Vettes, it would be a very good idea to hang onto the old parts.

05-05-04, 08:29 AM
Thanks rpounds. I guess now I just need to get those old manifolds in to the machine shop to be blasted. They're in a pretty sad state right now. At least is saves me a few hundred $ on headers.

05-08-04, 11:36 AM
Hello Bob-K, I purchased my 75 from Florida last Oct. it had straight through duels. I purchased the stainless Exhaust from Mid america and new mufflers,(front Y pipes,and rear Y pipes) I didnt notice any diference in sound or performance. Ive scence gone to side pipes, I have about 200 miles on the new stainless system from mid america. if yr interested let me know?, I have the reciept for 586, but might let them go for much less. Im in Bakersfield. and there just sitting around. good luck on yr move.

05-08-04, 12:40 PM
Don't suppose I get a free copy of the dyno results with that do I?
Well Unfortunitly they only run the car up to 25 mph, so you wouldn't get much help from the dyno data. I am not sure that if you are comming from out of state if you need to go to a smog only station, or just a regular station. If you just need the smog cert, you can usually get away with duel exhaust, but you would need to have 2 cats, no headers, and everything smog wise, including stock air cleaner hooked up and working properly. You might want to check into the requirement before you got crazy with replacing parts. You can also do a pretest, which does not hook into the system, I strongly recommend this as they have what is called a gross polluter designation. Once your car get labeled a gross polluter, it is very tough to get it off the list, you'll have to take it to a special judge who will give the care a very close look to see if everything is stock. I have not personaly gone down that path, but have talked to others who have, and it is a nightmare.

The next downside is the cost of the smog checks, figure $60 - $100, and if you do a pretest you have to pay twice :mad !

Good luck!

05-08-04, 12:59 PM
Thanks for the offer Chuck, but by the time I have it shipped to NY I'm probably better off going through MA...directly. I have a friend up here that is a distributer for them so I wouldn't have to pay shipping, which I imagine would be a lot based on the size of the items.