SP tails tamed and some nasty noises stopped

[Luckyone]

Some time ago I posted this link to old thread showing how I got my SP tail pipes to actually line up with the exhaust cut outs. Well in that thread I mentioned using cable ties to help hold them in place. To be honest this was a cr*p suggestion as they either melted or they just fell off.

Since I’ve had time to get out in my new pit I’ve been doing some investigations & found that when I fitted the system (TC linked de-cats, standard middle pipes & SP back box with their adaptor link pipes) I was trying to cater for the back box inputs & mounts being off set to the near side by loading up pressure on the down pipes to hold them to the off side against the will of the mounts (rubber hangers) at the rear. This meant that as the system warmed up & expanded the tail pipes moved, so along with cornering forces, the tails were never exactly where I’d left them after each drive. This was annoying, not least because of the cost of the system, but mainly because the much larger tails fill the cut outs much better so the slightest movement really showed up.
To fix it I removed the NS exhaust mount from the car, cut the bolt out of it & re-welded a new one in that had thread all the way to the mount, then I could adjust it up much closer to the chassis so it lined up with the wonky SP mount. The one on the OS had enough thread on it all ready to adjust out to line up. I then cut off the tabs that hold the two exhaust middle section pipes together & loosely bolted the whole lot back up into the car. I was very pleased to find the tails now just hung naturally in the cut outs (before I’d had to use the adjustment on the de-cats to get them into place). So I re-welded the links back in to the middle pipes & went for a bitter sweet test drive. To my delight I found the very worrying screeching noise that I’ve been trying to trace for more years than I can remember had vanished. This was great because I’d tried everything I could think of & everyone on here had suggested to stop it, but to no avail. So I’d managed to convince my self it was a bearing shell spinning in the engine & I’d all but stopped using the car for fear of an expensive break down. However there was still a horrible grinding noise every time I cornered hard & lots of bangs & thuds from the exhausts hitting the car over bumps on bends. I’d always known this was the exhaust because it started the monument I fitted it. (the other screeching noise took some time to start so I hadn’t made the association). The grinding noise is the manifolds touching the chassis at the front, just back from where they connect to the cats. It can look like there is quite a gap there but the engine moves quite a bit & they will touch. The gear box needs moving to one side or the other if you have uneven gaps, I tried this both ways but just moved the noise from right to left hand bends. In the end I found I had to bend the NS down pipe closer into the gearbox, do some good lining up of the mounts, then use the de-cats to pull the down pipes very slightly closer together too.
To stop the banging I added some extra mounts to stop lateral movement, most easily described by the pics. I think by using lock tight rather than a locking nut on my longer bolts the new (actually the old ones cut up) mounts would sit in a better place, but that’s were my development has stopped for now. Because after I’d taken it out for a test drive with this set up it was a different car, so thought I should treat it to a partial overhaul, but that’s a different thread (to come).

It did strike me just how much the whole standard exhaust system must move about as there is no lateral support at all, this puts a huge pressure on the down pipes as they are the only things giving lateral support, this must contribute to the cracks we get in them. Every time I went out for a test drive I put a new little centre rubber on & each time it had sheered off when I got back.

Here you can see, maybe not that obviously, the SP link pipes & mounts being offset to the NS. You can also just make out the extra mounts. The cable ties are just holding rubber to rubber now so I hope they will hold for a lot longer...



Here you can see the new mount being held in place with a longer bolt in the end of the chassis on the heat shield mount.



Here you can see how much I had to move the links between the middle pipes by the location of the bolt for the little (useless) centre rubber. Also visible are my sexy(?) bolt head protectors, made after a disagreement involving too low suspension fat bloke & bumpy roads…



(Sorry if anyone has an aversion to brackets I seem to have a bit of an addiction to them )

Edited by Luckyone on Wednesday 25th August 07:43

[stuthemong]

That is awesome stuff - I know exactly what you mean when you speak of transforming the car, mine is so much more fun with new pads - was pretty hairy when trying to scrub off speed before!

I actually have the same problem as you - albeit maybe not as severe - did you say you made new mounts near the engine side to stop gearbox clatter? If so, pics please! If not, is it just the improved rear mounts that stop left/right flexing?

Cheers

Stu

[Luckyone]

stuthemong said:

That is awesome stuff - I know exactly what you mean when you speak of transforming the car, mine is so much more fun with new pads - was pretty hairy when trying to scrub off speed before!

I actually have the same problem as you - albeit maybe not as severe - did you say you made new mounts near the engine side to stop gearbox clatter? If so, pics please! If not, is it just the improved rear mounts that stop left/right flexing?

Cheers

Stu

Yes, its amazing how much faster Cerbs are when you have confidence in them

This is of relevance to all V8 cerbs (I'm guessing 4.2 also) regardless of the exhaust system:
I didn't make new gearbox mounts, just adjusted the existing ones. Arrowed in red below are the mounts bolts, these have elongated holes under those heat shields that let you move the gear box left or right. If your clatter is just going round bends one way, move the gear box the other way a little & try again.


Edit - In this pic the de-cats & the big heat shield that runs all the way to the rear have been removed. Only the cats / de-cats need removing to get to these bolts. I'd recommend taking the bolts right out, cleaning them up & adding some thread lock as they are very short & you don't want them coming undone!

I suspect your gearbox clatter is what I was calling a grinding noise. This noise is actually the down pipes / exhaust manifolds touching the chassis rails at the locations arrowed in red again below, you can just see where the paint had been rubbed off on the OS:



As I was saying it can look like you have a good enough gap there when you are under the car, but the engine / gearbox move a lot & they will touch, making a very nasty noise. If you have linked de-cats you can try using them to pinch the down pipes together. If not the & it still rubs after all the adjusting of the mounts both ways, as I found, I then had to bend the NS down pipe in closer to the gear box. As can be seen in the pic there is a much bigger gap between the box & down pipe on the NS than the OS, so there is room for manoeuvre. Bending the down pipe on the car was very hard, I used blocks of wood jammed in-between the box & pipe to control the bending point, them stuck a very long bar that fitted nicely in the end of the down pipe (being careful not to damage the Lambarda sensor) then I huffed & puffed a lot...

Edited by Luckyone on Wednesday 25th August 09:45