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MG MGB Technical - What Exhaust System?

I was planning to alter the filters on my '72 GT to some K&N and some new carb needles to match. I was wondering what exhaust system would be needed (if any) to balance out the extra air coming in. I was advised by a freind to avoid Peco (problematic fitting and quality) and go with Double S. But i have no idea what one to get, 3 brach manifold, standard, free flow, sports, standard centre, bomb box etc....

I need some advice and hopefully experience of what other people have done.

Cheers
Kev

I installed the PECO exhaust but retained the stock header because the engine is basically stock. The new exhaust is fantastic! It was a bit tough to install but that isn't too unusual. The exhaust tone is the best I've heard and performance seemed to improve very slightly.
Steve S.

Kev,

I've fitted 2 peco big bore systems with the 2 cars I've had and had no problems.

They suit the K&N filters.

I bought them from the B-Hive, about £130 for the 3 branch manifold & the single box system.

Nick
Nick

I just installed a an ANSA exhaust system. I was actually surprised at how quiet and rich tone came out after I was all done...nice advantages though up and above the 4000RPM range unlike my old system. The new exhaust sounds great and goes great with my custom intake. Nice to have the dual crome tips out the back too. I recommend it to anyone
EJW Willis

Ken,

I've just bought the DoubleS big bore exhaust, as offered by the MGOC. Costs a bit more than the mild steel Peco, lasts longer (normally...)
It'll be installed somewhere next week. Email me if you'd like to here how things went and how the car sounds and feels.

Greets,

Alexander
Alexander M

I don't want to sound funny, but i'm still really mystified. Whats a bomb box versus a standard centre box??? Whats the difference between The Double S Performance system and the Free flow system???? whats the difference between a double tail pipe and a single??? If i know the differences and charactistics i can choose something to suit. I was thinking of getting the double S performance pack with bomb centre box from the MGOC - would this be alright for engine specs - original post
Kev

There is no practical use for a double-tip exhaust in an MGB. There is only one pipe from the header to the tail so putting an extra pipe at the last 4" of the system will do nothing. If you like the looks of it, great but it will serve no purpose.

It has been suggested before that dual pipes be run the entire legnth from engine to tail but this is a very bad idea. The engine needs the back-pressure created by the merging of the header pipes to keep the engine running smoothly and properly. Going to a slightly larger diameter pipe CAN help but not always. An exhaust system needs to be properly designed and setup for the engine it will be attached to. An improperly designed system on your car can destroy any other improvements you have made in the past. Just my 2 3/4 cents!
Steve S.

Kev-
To go back to your original question, if all you've done is install a set of K&N airfilters and richen the carburetion, you'll gain about 3 HP at high RPM, so your stock exhaust system will be good enough. If you want a higher-performance exhaust system to compliment future improvements, I'd recommend either a Peco system or a Falcon single-box system.

On an MGB the front muffler reduces low, bass notes while the rear muffler dampens high-frequency, rasping notes.

A "bomb" muffler is a small, cheap muffler that is rather loud and has a short lifespan. Here in the USA they're called "Cherry Bombs" (as in the very loud fireworks bomb) or "Glasspacks" (so-named because they're lined with fibreglass wadding to absorb the worst of the noise). Due to the design, a "bomb" muffler is very loud under acceleration. Pimply adolescents love them. A "box" muffler is what you see under a normal car: a box with some form of baffling system to disrupt the flow of exhaust gases and dampen the noise. I'll put it this way: "bomb" mufflers are a joke that will cost you lots of citations from your friendly local constabulary, "box" mufflers are worthwhile. A properly designed "box" system will actually outperform a "bomb" system due to their more sophisticated design allowing controlled back pressure.
Steve S.

Thanks very much chaps, your advice has really helped
Kev

Ken

I have a set of K&Ns, rich needles and a Peco 2" bore system with a single box. It sounds good and works a treat.

I've had no reliability problems either.

Bob
Bob Everick

As far as Steve's comment goes, indeed he is right in the fact that I am not getting any more "performance" out of my MG because of the tips but it does improve both the cosmetics and also the sound from the dual resonating tips..
EJW Willis

Hi everyone,

We can hear the double exhaust pipe Bs arriving at the unit from miles away, they seem too loud and I have a feeling they restrict power due to the sudden expansion from a single centre pipe near the tail of the box to exit two pipes at the rear. The noise is caused as the tail pipes are too large, it is common engineering practice to have the gases finally exit a system through a slightly narrower pipe....major reduction in noise output, minimal power losses....thats why the Peco system sounds great.

Another problem is with the accoustics of stainless steel systems....much louder than mild steel.

Yet another problem seems to occur with stainless headers...heat transfer is lower with the stainless and seems to increase the temperature in the exhaust ports....!

Peter
Peter Burgess

My two penny worth is to stay with the standard size of pipe and go for a single large box at the rear with a single pipe.
Chris Betson

This thread was discussed between 07/05/2002 and 10/05/2002

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.