About the benefit of some simple upgrades

[stretoo]

When I bought my car 10 month ago (FHC SI, 1967) the first thing that bothered me was high fuel consumption. It is generally the symptom of various causes to cure. At that time the car managed about 17 miles/gallon. The first thing was to perform the ignition timing, change the spark plugs (NGK5ES), the air filter and the fuel filter. Then I installed the electronic ignition (Lumenition Optronic) and checked the carburetor setting. The next step was to install a big bore stainless steel exhaust system (including manifold) and new heatshields (see: http://etypeuk.com/forum/viewtopic.php?t=2595). In addition and keeping the original fuel filter I added a fuel pressure regulator settled at 2 bars (see: http://www.etypeuk.com/forum/viewtopic.php?t=164). I have recently driven 1500 kilometers (or about 900 miles) on various types of roads and the car return a fuel consumption of about 23 miles/gallon. I?m quite happy with this result which validates the upgrades done on the car ignition and carburetion. I would definitely encourage doing each of these updates but the installation of the fuel pressure regulator is probably the first thing to start with as the result is so convincing. Not to mention the car is a joy to drive, she is fast and nervous.

[Bristoletype]

Hello Stretoo,
can you please tell me what big bore system you installed and whether I should also replace the cast manifolds with tubular? I've been thinking about this for some time.
Thanks for any advice.
Graham

[Heuer]

Graham

I have lots of experience in this area and it is a bit of a mixed bag. Firstly the cast manifolds suit the XK engine very well as they are designed to boost torque at low revs (2,000 to 3,000 rpm). If you replace them with tubular manifolds the exhaust gases have more room to escape which boosts bhp at maximum revs but causes a torque dip between 2,250 and 2,750rpm which is just where you need it for a road going E-Type. The solution is to fit venturi's in the silencers which help speed up the gases at low revs (i.e. work as an extractor) but the only company who do that successfully as far as I know are ClassicFabs. I have tubular manifolds and I am thinking of going back to the cast versions because at normal revs you get an irritating tinkling from the manifolds, under-bonnet temperatures are increased and that beautiful polished look quickly disappears with use. The big bore versions are a very tight fit between torsion bar and sump so you also get the occasional rattle! If you fit them you must fit a shield between them and the servo (on 4.2 cars) as the heat build up can affect it.

More info here: http://etypeuk.com/forum/viewtopic.php?t=287

Best combination for a fast road E-Type is cast manifolds allied to a ClassicFabs big bore silencer system. If you are going racing then tubular manifolds will be best.

[stretoo]

Hello Stretoo,
can you please tell me what big bore system you installed and whether I should also replace the cast manifolds with tubular? I've been thinking about this for some time.
Thanks for any advice.
Graham

Hi Graham.

Thank you for your interest and your question.

I bought the stainless steel Bell performance system (2 inch bore) from SNG Barratt which includes the 6 branch manifolds. My car is LHD so I had to modify the brake/clutch reservoirs heat shield to allow enough space for the front manifold. I also had to displace the dipstick bracket. The sound is very nice and not too loud, just what you need to be happy when the engine revs up.
As far as I am concerned I did not experienced any problem with rattles and lower torque. My engine is the original 4.2 L equipped with the standard SUs. My opinion after driving 2500 kilometres is that it works better than before, the car is very enjoyable to drive (and hear). I have not experienced the ?cast manifold/big bore silencers? combination, all I can say is that it?ll be friendlier to your wallet and probably easier to install...
So the choice is yours.