Exhaust Question for CA folks

Thinking about replacing the last section of exhaust system on my 79 B with either the Monza Free-Flow or a Big-Bore Stainless. Car has stock exhaust with cat converter, in good working order. Question is, will either of these cause a problem when I get her smogged down the road, and will either require substantial carb fiddling (Zenith 175 with manual choke, stock air cleaner)? Any guidance from California owners greatly appreciated. Sucks being post-75.

[edit 75 vs 73]

Ronn, you should be ok as the muffler is after the "CAT" and not part of the emissions system. You also shouldn't have to make any carb adjustments either, but that's the easy part if you do. Good luck.

Thanks Dennis. Whenever I've changed exhaust on motorcycles, I had to also change the mixture somehow to compensate for free-er flowing - usually changing jets or needles or shimming the needle. Wasn't sure if the ZS was similar in that regard. Any idea which of these two would sound better/work better? I think the Monza looks better but the Stainless looks more original.

I'm surprised that they don't call you out on the manual choke conversion. Technically, it's illegal in CA. The exhaust, as long as you retain the catalytic converter, should pose no problems. RAY

Yeah Ray - she was just smogged last month and he missed that (I don't think it was in his reference for this model) - he did notice the plugged connections that used to be connected to the automatic choke. He asked and I just said I dunno. She barely passed the CO at 25mph test. Hopefully I can get access to an exhaust gas analyzer before next smog is due (2 years). PO installed the manual choke BTW - I'd have been fine with the auto.

Ronn, there's alot of information on the big bore vs monza/ansa exhaust systems in the archives. You're going to get alot of differing opinions I think. For me it all comes down to individual preference, which I have no experience with, sorry. I wish someone would post a sound bite of the different exhaust systems and add it to the library. That way one could listen for themselves. But, if I did have to choose, I like the looks of the single exhaust. The dual tailpipe looks too much like a Triumph tailpipe, not that Triumphs are all bad, but we're talking about MG's. Just saying.

I've had the Big Bore exhaust on my '67 for almost 20 years and I couldn't recommend it any more highly. A great product, that lasts forever. When I first moved to California, in '95, my '67 just missed the cutoff date for emission testing by one year. I had to remove my Weber DCOE carburetor and re-install the dual SU carbs. I couldn't find my original distributor, so I left the Mallory Dual Point distributor in place. Fortunately, the inspector didn't know anything about MGs so it passed with no problems. RAY

Thanks Ray and Dennis. The Triumph point is well taken. I had a '67 Spitfire that unfortunately was totalled in '69 when a chick in a Camaro decided to pass me (at 60mph) on a 2-lane blacktop while I was turning left. Dang. Good news is we were not killed and her insurance paid me the Blue Book. But I digress. I like the idea of folks posting sound files of their non-stock exhaust notes. Any chance you could do that, Ray? Would love to hear it. Of course it would sound a little different on a cat car but still...

That would require me to actually start the car. It's outside in its garage, but I haven't even looked in on it in close two months. My bad. RAY

Oh Jeez Ray, we don't want that! :)

The dammed car has a better life than I do! Maybe this will motivate me to look in on her. RAY

Well, I guess I fit. I am (unfortunately) a long time victim of CA smog. My 79 has stock everything except I put on a stainless exhaust. I like the fact that it is basically maintenance free. Sound is no different than the stock setup was, as far as I can tell. Anything downstream of the CAT is OK, because only the cat is (an emissions related piece of equipment). Tuning is easy on the ZS because most failures are due to timing rather than the carb. Here's my advice. Regardless of your exhaust setup, keep the auto choke, cat converter and ZS carburetor, smog pump and all associated plumbing (air injection manifold, EGR, gulp valve, etc). For the test, lean the needle almost all the way CCW using the adjusting tool. Then block the vacuum advance (if you have it connected to manifold vacuum, like most of us) by putting a piece of tape over the end of the vacuum diaphragm connector, then plugging the hose back on. The reason for blocking the advance is that the stock setup was to use the TCSA valve, which prevented vacuum advance until 4th gear. So if you don't have that valve anymore, and I don't think anyone does, you need to keep the timing un-advanced (is that a real word?). Then adjust the timing to 10 deg BTDC and set the idle for about 900 or so to keep the idle sort of smooth. Fill the tank with gas, new oil is best and you should be OK. Some shops don't know about manual chokes, but the ones here in Truckee sure do. Very few, if any, smog controlled cars had manual chokes, so it's pretty obvious if you modify it. Good luck.

After you pass, there are plenty of posts that tell you how to de-smog until the next time. Not that I would EVER suggest doing such a dastardly deed!:)

Great stuff Vern - we should start a "Post-75 CA Smog Tips" thread. To get her to pass this time I did turn the needle the max counter-clockwise, adjusted idle accordingly, changed the plugs and air filter. Did not know about vacuum advance. Good one. Is vacuum advance different with overdrive? (Mine has it).

[edit - 75 vs 73]

Not that I would recommend it, but I've heard that some people have taken the VIN off of a pre 1975 MGB. So I've heard.

They register the car as an earlier car. A number of the mini owners do that. Just check out some of the minis on eBay.

Yeah I'd guess you'd have to register the (post-75) vehicle as the other (pre-76) vehicle but now you're talking some crazy illegal stuff.
Now, back to the legal stuff...

[edit 75 vs 73]

it's 75. Anything 75 and older doesn't need to be smogged

Thanks Gary - I made that correction.