Exhaust System
3000M
Manifold
A pair of 3 branch tubular mild steel manifolds, run down inside the chassis to under the gearbox.
Centre Silencer
Two inlet & two outlet pipes - one for each manifold. Low profile silencer for maximum ground clearance. Still has a risk of grounding so many re-made systems have skid plates front & rear, to stop the edge seam of the silencer getting folded. If no skid plate is fitted as standard it's advisable to weld one on each end.
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Rear Silencers & Tailpipes
One silencer for each bank of cylinders - these fit neatly under the chassis, have a rubber "cotton reel" type mounting plate with a failsafe "hook" style mount, so preventing the rear silencers to drop to the ground if (or rather when) the cotton reel mount fails. Fitting a stronger mounting rubber or even a pair of mounts here is wise.
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From my old website:
3000M Exhaust System
Overview
The exhaust system is tidy and tailor made for the 3000M, therefore should normally fit pretty well as there aren't many manufacturers who produce these. The manifolds (one on each side of the engine block) are a three-into-one branch design of non equal length as standard.
From this one pipe on each side is an angled pipe which allows the two sides to connect into a central silencer under the centre of the car, which then exits into two secondary silences (or resonators) which further dampen the engine noise. Finally each silencer joins to a long upwardly swept tailpipe which allows the exhaust gas to exit from the rear of the car.
On the standard system (although design may vary slightly) there is normally only one exhaust mount which is found right at the rear (see main photo at top), but the way it is mounted with its bracket means that even if the rubber mount breaks, the exhaust should remain suspended rather than hitting the road. The system relies mainly on the rigidity of all the exhaust components when they are clamped together.
The main problems with this system however, is the fact that the main and secondary silencers have to be mounted below the chassis bars, which obviously makes them very close to the road. With certain suspension setups the silencers can hit the road when driving over uneven surfaces, resulting in worn out silencer casings in a short space of time. See above photo.
Lifespan
The exhaust system is pretty good though if not constantly hitting the road, as the pipes are warmed up well by the large engine (large for UK cars!).
Servicing
Basic checks with the engine running are all that's needed to make sure the system has no leaks, and that all joints and clamps are satisfactory (marked above are the front two joints). Look at the rear mount metelastic bush to see if there are any signs of splitting. Expect to change this bush about once or twice a year if the car is used regularly.
Performance
The standard system is adequate for standard engines, but once any extra power is wanted then this is the first item to replace. Firstly, the manifolds have unequal length branches to the point of blending into one, and the point at which they join is not particularly well designed for gas flow. Of course this varies depending on who made your system. Also, the bend on each pipe near the gearbox where the exhaust changes direction to run horizontally under the car can be poorly made when the pipe was bent. The result is gas flow is impeded (see photo below - pointer shows pipe diameter has been reduced due to bad forming):
The rest of the system has also been made with cost savings in mind, the silencers being hand made with no provision for skid plates to save the silencers from grounding. If a kerb or similar is hit it could cause serious damage to the silencer and/or system - possibly resulting in the whole thing being pulled apart.
Noise levels
The noise level of a standard exhaust on a 3000M is approximately 110db - so reckon on being asked to fit an additional silencer if you go to a track day. In fact to reduce it below 102db (or even 98db at some tracks) will not be easy, and if you are faced with this on the actual day without any mod's ready then expect to lose your deposit!
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