I know on our P types there is practically nothing to prevent engine vibrations being transmitted to the chassis, so will it matter if the exhaust mountings do not allow for any movement between the pipe/box and the chassis? Has anyone experienced damage occurring to the manifold or exhaust system , as a result of this lack of independent movement?
The most common cause of damage to the manifold is when removing the downpipe and the lugs snapping off.
I do know that the manifolds are prone to damage by impacts to the underside of the downpipe and silencer (normally during trials).
The best idea is to use a reasonably flexible mounting which keeps the pipe, silencer in straight line and avoids any rubbing against the undertray - or the silencer hanging too low.
On the NA we use a rubber strip mounted on brackets attached to the chassis and the pipe. The first mounting is just behind the silencer and the second is behind the number plate on the tail pipe. I find that the standard moutings hold the pipe too high for the larger than standard silencer we use (the standard silencer is a bit on the noisy side because the packing does not seem to last very long) I find that this rubber strip is flexible enough to withstand the odd knocks and scrapes.
The most important thing is the down pipe alignment. Often the pipes get damaged and as a result the whole system starts off pointing the wrong way.
Do not try to straighten the down pipe when fitted to the manifold - the manifold is too delicate (and expensive) and easy to damage. The whole system should sit parrallel to the ground and the underside of the car - the pipe and silencer should be well clear of the chassis, undertray etc.. so that it cant rub or vibrate.
Keith if you are using the original L brackets to mount your exhaust you can get enough movement to allow for expansion and chassis flexing by putting a plain washer and then a double spring washer ( thackeray washer ) between the bracket and the chassis. Use a lock nut to keep the washer in part tension. MG used several plain washers and an ordinary nut then peened over the end of the bolt to achieve a similar result.
It is quite surprising how much expansion and movement there is in the exhaust system.
The reason I posted this topic is because I had made the L type brackets, but use the exaust U bolt clamps at each end of the silencer to connect to the L brackets, providing very solid supports, but with very little flexability. I will now see if I can adapt the brackets to use the double spring washers you suggested between the chassis and the L brackets you mentioned.
With regards to your comment on engine vibration through the chassis there is rubber on the front engine mount and on the gear box cross tube. However, this is still very solid. You may know that I designed a P/N cross tube mounting to replace the unattainable cross tube mounting bushes. Many of these that have fitted these new bushes have commented that their car seems a lot smoother and with less noise once these have been fitted. I can only assume my design adsorbs more of the engine harmonics. Regardsą. Terry
Forum Locked
Topic Locked
Posted - 04/11/2009 : 09:01:48
I can only assume my design adsorbs more of the engine harmonics. Regardsą. Terry