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MG MGB Technical - Exhaust system advice

I'm currently evaluating what I need to do to my '79 MGB this summer, and one thing on my list of "maybes" was the exhaust system. I'm not sure what's on it currently, but the muffler is fairly new and round (not oblong). The major problem is that the PO, instead of getting a nice chrome tip to get the muffler end out past the chrome bumper conversion, welded on about a 6" piece of rusty old tubing. Ugh...

Anyhow, that's not my problem. The problem was that, when I crawled under the car to see what the condition of the system was, I was horrified. The downtube and tube from the catalytic converter to the muffler (only one muffler) is corroded all to hell, and a few small holes have started to form. As I said, though, the muffler is fairly new, so I'm not sure I want to replace everything. The header has some surface rust, but nothing major -- I could probably take after it with a wire brush and it would clean up nicely.

What advice do you guys have about what to replace? From what I've read, the exhaust system isn't a big bottleneck on the B series engine, so I probably wouldn't see much of a power gain, especially if there's already an aftermarket muffler on there. Should I just take the car to Midas (*shudder*) and have them replace the tubing? Get a new system from the cat. converter back? Go crazy and replace it all? I know you all are shy, but don't hold back. :)

Additional details: Engine has been bored out 30 over, Weber downdraft carb.

Thanks for your advice.
Chris St. Pierre

I have to replace the exhaust on mine. Everything back from the header. That I did just clean up with a wire brush and it came up fine. It will rust again I know but I couldn't find a paint locally that would be certain not to peel and I couldn't justify the expense of having it hot coated. As for the rest I was going to go with the standard mild steel exhaust minus the centre muffler. I've heard the stainless ones can sound tinny? Maybe someone who has one can comment. I want the car to sound sporty but not loud. I think the standard setup minus the centre sounds right. I can't stand the loud, droning exhausts. Especially the ones that change pitch with every change in throttle position. Like the jap boy racer ones that go up the road sounding laboured and droning mmmMMMMmmmMMMMmmmMMMMMMmmm. I REALLY hate that!

If you're not doing any mods to the engine apart from say fitting K&Ns on the intake side is there any point doing anything to the exhaust on a B? I know in the states you guys have some other options than just standard that sound good but down here trying to put together something might be somewhat hit and miss as to what sound you get at the end.

Simon
Simon Jansen

Did they (PO)not ditch the Catalytic convertor when the Weber was added?
Frank

1974.5 non-catalytic RB MGB, Weber DGV conversion (PO). PO had a Monza exhaust which I found very loud. It also had a loose baffle and rattled like crazy. Decided to replace. Ordered a mild steel exhaust (which turned out to be a Peco) from the Proper MG (about $149 US). The system has a cherry bomb type center muffler with a cylindrical rear muffler. Retained the stock exhaust manifold. I am happy with the results, the car has a nice sound while not being too loud. I didn't want any of the Midas type products.
FWIW, I would dump the cat (if allowed in Nebraska), and install a new system from exhaust manifold back.
John

I just ran a custom 2" system on my '71. Its a Thrush turbo muffler (very short and oval) next to the gas tank, and 2" pipe with a single offset under the axle. It performs very well, sounds good at idle, and gets surprisingly quiet at highway speeds. 17702 is the muffler part number, and I picked it up at Advance Auto Parts for $45. For a total of $105, it sounds and performs better than the Ansa system that's in my shed.
Jeff Schlemmer

Nebraska has nothing even approaching emissions standards -- you see more blue-smoke-belching crapmobiles than you can count. Heck, I used to drive one myself!

The car came from the Colorado frontrange, though, which has very strict emissions requirements; that's why the PO kept the cat., I suppose. Personally, I have no special desire to keep it on there. If I'm replacing everything north and south of it, it might as well go, too.

Jeff- That sounds like a nice setup. I assume you also ditched the catalytic converter? How much welding/bending did you have to do? (I'm skilled at neither.)
Chris St. Pierre


Chris!

I just replaced the exhaust system on my '80 LE. ' Got a stock head pipe, and both mufflers from The B Hive. I think the total cost was around $120 for everything. Mine needed new exhaust hangers as well. I'm impressed with the sound of the stock system. On the other hand, my '77 has a Monza rear muffler ( installed by PO) that is okay. My TD has a stainless system from Moss. I'm not crazy about how it sounds ( way too loud). ' Guess that's to be expected since the T series only have one muffler. Anyway, there are several different options you can take, but if you have the stock carb and converter, why not just run a stock exhaust system?

Cheers,
Dave
Dave Plantz

78 B. Muffler separated @ the rear hanger. Took it to Midas (they were the cheapest). Installed new exhaust from headers back. Cat was so bad, that some of the guts fell out @ the garage. Cost $300.00 for new exhaust, muffler, and resonator. I didn't have a resonator originally. The exhaust is also lower to the ground than original. Going to take it back and have them raise the entire exhaust 2-3" if able. Any sites that I can go to that shows correct installation measurments? What's resonator for? They installed it a couple feet in front of the cat converter.

shook
Shook

The resonator is an expansion box, it lets the header do its job with the scavenge effect over a wider rev range. I have a 2" Faclon stainless single box with steel LCB header on my car. At the chairman's run this year someone told me they like to get behind my car to listen to it! Now if only someone would say that about my singing.
At the natter once one of the other regulars drove it past for me ( oh those warm light summer evenings), one way on a light throttle and the other gassing it, what surprised me was how quiet it was when not working hard. This system is not really loud in the car, but for a daily driver I would not go that way. I always liked the sound of the factory no cat set up it has a sort of turbine whoosh and resonant hollow boow at 2000 rpm that says MGB even when you can't see the car. We followed a neat roadster with a stock setup on the Cotswold run last month and it was pleasure to listen to it.
I think my all time favourite exhaust note is a Manx Norton being wrung out by someone who knows what they are doing up to the Bungalow in the IoM TT
S Best

Chris,

I have a "77 B and awhile back I replaced the exhaust sytem with one from Victoria British. I ordered the system that was for the 76 B w/o the converter. It came with the pipe that takes the place of the converter perfectly. I had my local tire and muffler shop do the replacement. Just brought in the parts and they did the job, for a fee of course. But it was much nicer that way than for me to try to do the job, and it was done correctly.
Don Elliott
Don Elliott

This thread was discussed between 09/05/2005 and 11/05/2005

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