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11. Fuel System
Manifolds
The inlet manifold is alloy so just needed a good clean. However, the
exhaust manifold needed rather more attention. When about to fit the
manifolds, I discovered that the flanges were different thicknesses so I had to
make up some half
washers to build up the thinner inlet manifold.
Carburettors
Here I fancied a bit of a challenge! My donor carburettors are SU HS4s and new
ones are not cheap so I decided to recondition them. I had never stripped an SU
carb down before so I thought it about time I investigated how they really
worked! I took everything apart and thoroughly cleaned it. I replaced jets,
needles, floats, throttle spindles, discs, etc. and, yes, I did find out how it
all works. I just had to shine up those dashpot covers too! One bit of advice
though - only do one carb at a time. Then you can use the other for reference!
The service kit came with very useful instructions and diagrams too.
Heatshield & Carburettor Blocks
There is apparently insufficient room under the NG bonnet for the carburettors
and air filters to be fitted with the standard spacer blocks. NG supply (in the
fuel system kit) cut down blocks (8.5mm instead of 29mm), shorter carb fixing
studs and pancake style air filters. Because of this the carbs are nearer to
the heatshield which
needs to be modified so that the throttle controls clear it. Unfortunately, I
found that the throttle control lever was too near the exhaust manifold so I
have made up some slightly thicker (11mm) carb spacer blocks which just provide
enough clearance for the throttle. The
accelerator and choke cables were fitted later.
Fuel Supply
I opted for the stainless
steel fuel tank which I primed with Hammerite Special Metals Primer.
The tank support straps were "lined" with strips of rubber supplied. I
purchased a new SU AZX1307 fuel pump and mounted it in the standard MGB bracket
which is fixed to the SVA cross member (near the seat belt holes). A flexible
fuel hose connects the tank outlet to the pump and another connects the pump
outlet to the fuel pipe. The latter is fitted with some difficulty through
various parts of the chassis to the front end where it connects to a
filter and then on to the carburettors via more flexible hoses.
After obtaining the body shell, I found I had to
re-route the fuel pipe slightly in the area by the rear offside chassis
member. Although warned in the build manual, it is difficult to determine the
clearance needed without knowing the exact shape of the body. Also, once the
body was positioned, I was able to make holes for the
fuel tank filler and filler cap.
Exhaust
I decided on the Peco 3-piece exhaust system which is recommended by NG and for
which they can supply fitting
brackets. This is a straight through system of solid quality which
gives quite a good ground clearance (essential to me as I have a steep ramp to
the garage!). The build manual suggests reducing the bend in the centre section
and that it can be done without heat. I could not do it even with heat! Only
after cutting a "lemon slice" piece out and applying heat could the pipe be
unbent. I reckon the angle has been reduced from about 15 degrees to about 8
degrees and the fit is near perfect. The slit then has to be welded. I am told
it is possible to fit one of these with very little adjustment to the bend -
perhaps when it is time to replace it, I'll try a different tack!
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