Aug 242013
 

The exhaust system is another area where there are a plethora of options available and with them, opinions on which is best. These range from a standard bore with cast manifolds through to straight through, big bore pipes with either long or short tubular manifolds and all combinations in between. Advice often just reflected what the owner had decided to put on their car rather than comparative tests.

The Classic Fabs long tubular manifoldsIt was tempting to go for one of the tubular manifold systems from companies like Classic Fabs, which are a work of art.

However the administrator of the E-Type forum had done a fair amount of research backed up by practical experience, having fitted most of the different types available.

The general consensus from the forum discussion was that the original cast iron manifolds were very well designed; providing optimised gas flow to speed up the exhaust gases therefore improving low down torque but also heat management. The larger bore systems, specifically when used for the secondary pipes, can result in a torque dip lower down in the rev range.

The other issues are that they are more prone to grounding and tubular manifolds generally radiate far more heat which is then likely to cause other problems, such as brake issues due to the proximity of the brake servo and blistering of the paint work.

The Mikalor style clamps were used instead of the typical U clampsIt therefore seemed sensible to stick to the standard cast iron manifolds and 1.75″ bore system, which was purchased from PD Gough based in Nottingham.

I’d also decided to deviate from the original look at the rear after seeing others who had successfully avoided the slab-like appearance by removing the rear, brushed aluminium panel. The car will be fitted with a long rather than square number plate which enables straight exhaust resonators to be fitted instead of the standard S2 splayed ones.

The final decision to make was whether to have the system made in mild steel or stainless steel. Apparently mild steel gives a much nicer exhaust note but in the end I went for stainless for longevity. Another recommendation that I also adopted was to fit Mikalor style clamps as they apply the clamping force more evenly and avoid distorting the pipe joints.

Some ‘reject’ manifolds were picked up quite cheaply at the SNG Barratt open day – they had some tiny imperfections in the vitreous enamel finish which I still struggle to find. This finish was never very robust and had a tendency to crack and flake off. So I’m expecting it won’t last too long and will need to be removed in order to paint/treat the manifolds.

The engine installation weekend was fast approaching so I decided to trial fit the exhaust system. At this stage, without the engine in place, all that could be trial fitted was from the muffler section backwards.

The combination of not having the down pipes installed and the car being on axle trolleys meant it was extremely difficult to build the exhaust on the car. The pipe ends were unblemished so the system clearly hadn’t be bench fitted when it was manufactured. Therefore all the joints were still very tight even with a generous coating of Copperslip.

It was necessary to build the system off the car to have any chance of aligning the brackets on the intermediate pipes and to push the resonator pipes fully home to be able to mount them onto the rear hanger.

It was then fitted as a single unit, first fitting the muffler section to the four rubber mounts fixed along the chassis rails. I was struggling underneath the car trying to hold up the exhaust up to the mounts while feeling for the 1/2″ spanner that I’d dropped when I noticed I had an audience – a metre long grass snake was observing my progress a couple of feet away. I assume having taken refuge from the hot, sunny weather.

Mounted centre muffler section My new helper! Resonator pipes mounted at rear
The muffler section fitted fine .... until the resonator pipe were mounted which caused it to rise at the rear A grass snake had sought shelter from the hot, sunny weather The resonators had to be pushed upward with a fair amount of force in order to attach to the rear mount

The connecting brackets between the intermediate pipes and the resonators were all fixed so the whole exhaust was now quite rigid. The muffler section was already mounted but the resonators needed a reasonable amount of effort to push them up to reach the rear exhaust hanger. In doing so, it caused the muffler section to raise significantly at the rear so the output pipes hit the rear floor stiffener.

The output pipes from the muffler section foul the rear floor stiffener so something's amissIt didn’t seem right because the small rubber mount at the rear would be under considerably more stress than just supporting the exhaust’s weight. Apart from varying how much overlap there is in each joint, there is no other scope for adjustment and the geometry is fixed so, without modification, the pipes would almost certainly foul the rear floor stiffener.

I emailed PD Gough with the photos above explaining the issues I was having and the purpose of the trial fit was to ensure it fitted correctly before the engine installation weekend. I didn’t want to find out it didn’t fit during the installation weekend and therefore stop the testing of the engine.

I felt their response was more of a fob off and so wasn’t too impressed – “they’d never had any fitting issues before and would be surprised if I had fitting problems once the front pipe are fitted as they would generally bring the system into alignment”.

Personally I’m not convinced because the front pipes are flexible and so their ability to bring the whole exhaust into alignment would be limited. Also the forcing of the muffler section towards the horizontal to stop the clearance issue will only add to the stress on the rear rubber mount.

I’m going to be extremely annoyed if I end up having to ‘surprise’ them by informing them it doesn’t fit.

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