Westfield Elevens

Right, my turn to face the music. I have a track day booked with a 105db at 50cm. Measured mine last night with the cone in and I am slightly over although that may be due in part to some mechanical vibrations that I have yet to trace. So I have decided to repack the silencer and fit the half moon restrictors in the perforated tube. I have drilled out the rivets at the outlet end and tried to drive out the end cap by putting a stick up the exhaust and whacking the end. No dice, what am I doing wrong?

Is it a standard XI exhaust, Matt?

Maybe the guys on the Boardroom might be able to offer some suitable techniques?

Yep, standard Westfield XI exhaust.

Cant comment on the westy backbox but what i will say is dont over pack it!! I gained 4db over packing mine and came in at 108db!!
Never been over 105db even with an empty can.
Only pack it about 1/2 to 2/3 full and dont pack it in tight, once we repacked ours correctly it came in at 103db

You need to drill out and punch clear the rivets at both ends of the can. Then it should come apart OK. Soft hammer on the curved outlet should do it. Suggest you mark the can for orientation to the ends as the hole pitch varies sligthly in practice and getting it back together is much easier if it goes back the way it was.
First & second time I used the Demon Tweeks re-fill but third time I used Thermal Velocity's Acoustifil mat (see their website). 1 metre just does the Westfield silencer nicely - forget what width (450mm rings a bell) but there is one that matches the length well. It works our slightly cheaper than Demon Tweeks and to Adam's point does not "over pack" the silencer. Seems to be holding out OK so far.
I keep thinking I need something more effective but there is such a variation in sound readings at events the stock silencer seems OK so far. I've been up to 107 at one event only to have 102 at the next...with no changes.
Not had to use the dreaded cone yet!

As its a road car i would use the stuff Charles is suggesting, personally i use loft insulation
works well for the noise test, does tend to either melt into large clumps or get blown out completely after 2-3 races (if i'm lucky...)

we have tried using the correct stuff before but again it ends up disappearing albeit at a slower rate.

Yeee-haah! Club motor racing - duct tape, Araldite and loft insulation! That's the spirit...
All smacks a bit of the Yorkshire hillbilly's that used to run that crossflow Eleven. Whatever it takes.

I've just finished repacking mine after repairs were made (dented on a Combe speedbump!).

I used stainless steel wire wool around the central pipe, wirelocked into place, and e-glass wool. All available from eBay.

http://www.ebay.co.uk/usr/mijexhaust

I suspect I have overpacked it, but seeing as drilling out and replacing the 4mm stainless rivets has given me a hernia, I'm going to try it as it is, before committing to mods!