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Will be reinstating the 1275 S lump back in my Mk1 in the next few weeks and would like to make a few changes. Will be running a pair of H4 carbs, maniflow steel inletand LCB with a nicely flowed head. Currently run a stainless single box RC40. Thinking of fitting a twin box Maniflow system instead as stainless single box too noisy inside. Question is which Maniflow? Seems there are 1.75 to 2 " systems and not sure which would be most suited? Any pointers folk? Cheers. Mark

I would think a 1.75 twin box would be correct for your engine. Not sure it would be any quieter than a twin box RC40 though.

I'd say 1.75"

The Maniflow is more robust than the RC40, but if minimal noise is the priority, then the RC40 is hard to beat. On a mildly tuned engine, I don't think there is anything in it power wise.

I have found that there really is no need to go any bigger then 1.75" for the street, low end power is also better.

In regards to twin Box vs Single Box, in regards to the RC40, I've found the exhaust volume the same with both, however when running Cams generally over the 280 degree mark, the twin box takes the resonant note out of the exhaust and so make a far more even exhaust volume right through the rev range.

ive always liked rc40s, particularly as they look more correct 'out the back', and I don't think the quality is any better or worse than a maniflow

(although the maniflow that's on one of my gtm has gone very rusty after a years use, where the rc40 that's on my mini sprint is still mainly silver paint, and that's after 6 years of use).

A single box RC40 will not pass our local "MOT" noise regs whereas the twin box is quite acceptable.

As far as durability... I have a new RC40 that I bought in 2006 still sitting in the shed waiting for the (mild steel) one I bought in 1989 to die.... Up until recently the Min was my daily driver. Admittedly I live in the country so the exhaust heats up quickly (60mph limit starts about a mile from home) with virtually no idling at lights.... Its pretty battered consequent to the 1/2 mile of special stage that leads to the house.... but shows no sign of giving up in the near future....

Cheers, Ian

If you want a quiet exhaust, I can recommend my old course of action. I had a home made system which was a bit excessive, ie:- a cherry bomb non-silencer. It irritated the village, so I replaced it with the back box of a 2L TDi Audi 80 estate. Centre exit, single box and almost silent.

It was pretty much the case that the engine was louder than the exhaust whilst stood at the back of the car.

I am a big advocate of allowing a mini to breathe properly, even if it does make a row. If I wanted to shut one up, the first thing I'd seek is an A80 backbox. Amazing things. I think it had some big loose baffles which took the bass and mid right out of it and then a deflector thing and absorption "stuff" which took the treble out. It was not at all restrictive.

1071 S wrote:) one I bought in 1989 to die....

I think we have a winner!

I have a brand new rc40 on display that's date stamped 1995 - I wont sell it as ive had it so long!

Have they started painting them again then rich ? Instead of that crap zinc coating, they changed over to.

I put my Mk1 1275 'S' on the road with a twin box RC40.

Far too quiet for my liking and certainly didn't sound as good as my 998 Cooper with a single box RC40.

Swapped it for a single RC40 (mild steel) and it sounds brilliant (in my opinion). Certainly noisier than a twin box.

Stainless exhausts sound different to mild steel systems.

I had a single box RC40 on my Rover Cooper. It sounded great with a nice rasp to it. When that eventually rotted off, I replaced the whole lot with an LCB, deleted the cat and fitted the twin box 1" 7/8th Maniflow. It sounded fantastic and with a standard airbox, cruising under light load wasn't much noisier than the standard system. It didn't half bark at about 4k under load though - setting off car alarm kind of pressure waves used to come from it. Must have really irritated people in multi-storey car parks!

I plan to put a smaller maniflow single box on my 850 in homage to that car

Hi Mark
Could you not use a new centre section with a muffler box and keep your stainless RC40 back box?
I've not had a mini on the road for a few years so things might be different now but I've bought quite a few of the old steel RC40's and only one maniflow system, I think they're much better quality. Sure the RC40 looks more standard but using them on daily drivers in all weathers really shows up the difference in quality. My maniflow has been on 2 different minis (well over 50,000 miles) and is waiting to go on the next if it ever gets finished. I found the RC40 works well but looks pretty sorry for itself after a couple of winters if you actually use the car. If you want it quiet though stick with the RC40, the maniflow is a good bit louder system for system and has a very raspy note at higher RPM. Cant remember if mine is a 1 3/4" or 1 7/8" but its a single box and its very loud as they get louder with use.
Ollie