Exhaust repacking

[MG David]

I know there are exhaust experts on this site!

The Peco HDR single back box on my MGB sounds as if it has lost its packing. I have found an article on the web about repacking silencers.

http://www.mgaguru.com/mgtech/carbs/ex103.htm

In that article he uses glass fibre insulation as sold for residential use. The last time I bought such a material it was rock wool instead. Would rock wool be any good? Some of the insulation on B&Q's website is described as Glass Mineral Wool. Would that be OK?

 

[malcolm]

Rockwool is often used in silencers - it's supposed to be better acousticly than glass. I don't know if that's a different type.

Not convinced the thin lightweight stuff in those photos would last for very long. You can get a big bag of glass strands from Milner Offroad for about £10, and that's roughly the same as the standard material.

I like the funnel trick.

 

[MG David]

"Not convinced the thin lightweight stuff in those photos would last for very long."

So if the domestic insulation stuff is a bit lightweight does that mean I could use chopped strand mat or continuous glassfibre filaments? I had assumed it needed to be soft and wooly.

 

[malcolm]

I wouldn't use chopped strands - there's a fair bit of air going backwards and forwards past the perf pipe, so something not chopped would be best.

Here's the stuff I use. I think they call it e-glass.

 

[Chipper]

I got mine from NF Auto. Though someone on here (Sam maybe?) said using stainless wire wool was good.

 

[MG David]

Thanks Malcolm. I have now bought some on ebay.

 

[RichardM]

If you put a layer of stainless wire wool around your perforated tube and then glass fibre outside of that it will last longer.

 

[MG David]

I have now repacked the silencer and put a plate over the hole secured with self tappers and sealed with gun gum. Once the gun gum has dried I will start the car up and we will find out if it has worked!

Unlike Barney, in the link I posted, I don't own a hole saw so I made a rectangular hole using a 7mm drill for the 4 corners and a cutting wheel in my dremil to join them up. The long strand E glass went in easily so I didn't need the cardboard funnel and I used a paint stirring stick as my a prodder.

The car was measured at 102db when scrutineered at Curborough in April. I may have gone a little low on the revs as I was concerned it might be high. It will be interesting find out what the reading is when it is scrutineered at Silverstone in early June. The limit there is 105db.

Sorry for not taking any pictures

 

[MG David]

Just a little bit more feed back.

The car was sound tested a Silverstone yesterday. I gave it the full 4000 rpm (being 2/3 of the red line of 6000 rpm) and the reading was 93db. So I am very pleased with the result.

 

[MG David]

Just a little bit more feed back.

The car was sound tested a Silverstone yesterday. I gave it the full 4000 rpm (being 2/3 of the red line of 6000 rpm) and the reading was 93db. So I am very pleased with the result.

Thanks for the help.