I have a 998 mini with a maniflow lcb. I bought a Sportex rear box from Minisport but it is far too loud.
I obviously should of got a twin box system.
My question is should I add another silencer to the Sportex or should I just replace with a more quieter system like a rc40 twin box or something similar?

I just added an $80 cherrybomb [[edit] hotdog resonator in the tunnel. Worked for me.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

+1

A single box RC40 won't pass ACT rego checks but the twin box is fine.

I would look at the cheapest route to Kev's solution.

Cheers, Ian

Thanks. Is it much quieter now after fitting a cherrybomb silencer?

Still has a good note but the raspy bark has gone.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Would you consider the noise to be within the legal limit?

Yes. It is quieter than the Dellorto carby's induction noise now.

[edit] cherrybomb is an american term, it is actually a `hotdog' here. I picked the wrong word...
You can get them at any muffler shop, I welded mine in.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Ok cheers mate. What back box do you have?

I have a 2" system, the rear muffler is a diagonal pipe glass filled oval 'turbo' one.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

To get mine quieter I went to my local exhaust shop and told them I wanted it quieter - what did they have?

They went to their stock and found a muffler that would fit under the car and put it on. Hey presto the car sounds pretty good and is now not too loud.

Was cheap too. If I recall it was $100 fitted. I think you can muck around with RC40 and all the off the shelf mini shop but the best answer is go to your local and see what they can do.

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Cheers
Alec
1275LS - July 78 - XNFAD18Y/102918

Cheers Alec. I never thought about that. Certainly worth a try.

I did the same. I bought the 2" bore turbo muffler then crawled under the car and measured the pipe lengths needed, and angle (30deg).
I then went back to the muffler shop and got two 2" pipes cut and bent.
Crawled under the car again, fitted the muffler to the pipes and clamped them. Removed assembly and MIG welded the pipes in.
When later I fitted the hot dog in the tunnel, I did the same again. Cut the front pipe and MIG welded the hotdog in.

Note the 2" pipe was a slip fit over the Y piece of the Maniflow med bore LCB.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.