I hate exhausts

I've officially decided that I hate exhuasts. Both cars are suffering with problems, and both are causing me headaches.

The SD1 has a strange raspy/metallic knocking noise (hard to describe) when you hit about 3.5krpm. It's been suggested than a slight exhaust blow early on in the system could cause such a noise, so I've been taking it all apart and replacing downpipes and gaskets. The new o/s downpipe went on fine, with all new manifold gaskets/seals. The tried to put the n/s downpipe on and discovered it was about an inch too short. Damn. So put the old one back on (which was ok, just a bit old) and snapped one of the manifold studs. Double damn. So the manifold has been down a machine shop today to get the stud replaced. Hopefully it'll go back together ok when I get chance to get back underneath.

Then there's the Pug. It has near enough the same manifold/downpipe arrangement as my old 205 XS, and that used to piss me off too as it's an arse to get the downpipe/manifold join sealed properly. Dunno why, maybe it's just me. But the 106 hasn't been right since I did the top end overhaul a few weeks ago so decided to have another go at sealing it and also replacing the knackered manifold (the inside of it was broken meaning it was 4-1 rather than 4-2 IYSWIM). This revealed the flimsy downpipe has got a split in it where the metal has fatigued near the flange. Triple damn. So the replacement manifold is now on meaning it's 4-2-1 as it should be, and I've piled in the exhaust putty to try and stop it blowing, which has kinda worked. The cheapest downpipe I can find is £62 delivered and for a little bit more I should be able to find a proper tubular 4-2-1 manifold (which incorporates the whole downpipe and joins to the standard cat), so thats what I'm now after. They look pretty shit hot too - ideal for the motorway commuting car(!)

So there we go, I fecking hate playing with exhuasts. Rant over.

Reply to
Carl Gibbs
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You realise that cast manifolds are quieter and tubular ones noisier dont you?

Wonder why the rover ones dont fit.

The broken 4 into 2 into 1 bit giving 4 into one wont make much if any noticible difference really. But it should give less mid (around 3k) and more top (around 6k). But its going to be very minor...

Reply to
Burgerman

It's got a silly Janspeed backbox anyway, so it's already loud. And if it fits better and seals better I'll be more than happy.

It's only one that doesn't fit, which is a bit weird

Yeah but the metal is breaking off and rattling about in the downpipe/cat so it definitely needed replacing!

Reply to
Carl Gibbs

Loose baffles.

Reply to
Conor

I think he means quieter as in doesn't vibrate at 3500RPM.

Reply to
Conor

Fairly common. When I was on the original exhaust I had to replace a downpipe and the same thing. Luckily the car was still quite common at that time and the factor had three in stock - all different lengths. That was the N/S one too. Got one that fitted, though. When i got the SS one from Rimmers (on special offer) I decided not to get the downpipes due to cost. Plus the fact that steel ones are quieter. Same thing - the new SS one wouldn't fit the downpipe on the N/S. So had to buy the SS downpipes.

Had that too. Now use brass nuts. Kwikfit etc throw away brass nuts and fit nice new shiny steel ones. Which rust and snap the studs next time around.

It's possible the acoustic wadding inside the silencer has failed - that tends to happen to an old silencer. So saying non of mine lasted long enough for that to happen - but it did on my BMW E34 with just the sort of unpleasant sounds you describe.

If you're keeping the car an SS system makes a great deal of sense. Mine is over 10 years old and has more than paid for itself in lack of replacements - the rear silencer in steel rarely made much over 2 years.

Reply to
Dave Plowman (News)

Well the old one is back on now - I was only changing them because I got some NOS ones cheap. I'll just stash the new n/s one away - might come in handy one day for future SD1 projects!

Yeah that's probably a good idea. The new ones are steel because that's what came with the downpipes. Might invest in some brass nuts at some point before the new ones rust on :)

I've already got the stainless steel exhuast from the downpipe back. If I had the money spare I'd buy SS downpipes too. Maybe after the wedding!

Well the exhaust does sound a bit better - I reckon I've cured a little blow or 2, but the annoying noise is still there. It first happened after I put the SU's on with the K&Ns, so decided to quickly put the standard induction stuff back on (something I've been meaning to do for ages) and the noise was gone - at least it was whilst revving the engine on the drive. So I think I need to mount the standard airbox properly, get a new carb tube without the hole for the FASD and see how that sounds.

But why would the K&Ns cause such a noise?

Reply to
Carl Gibbs

Me too, the 306 only has half a one at the moment

Reply to
Abo

Me too - the Activa's centre box is rattling like a goodun at the moment. And I'm bloody certain the sparesmobile I scrapped had had the centre+rear done (relatively) recently too.

Caused by a moment of impatience whilst picking my car up from the station car park having parked it there the previous evening - I can get away with driving a fair few metres with the STOP light still lit at the two places I most regularly drive away from (home and work), so am used to not instantly worrying about it, but I parked quite near the entrance/exit, and there's a speed bump on exit - it briefly crossed my mind, but I vaguely thought "nah, it'll probably be alright". So that's 200 quid's worth of centre+rear boxes, unless someone knows a good cheap source of exhausts (or a Xantia nut that might have one going spare....)

Reply to
AstraVanMann

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