QuestionQUESTION: i just bought a 1977 MGB and the tachometer isn't working. Can you give me any info on what the problem may be.
Also i would like to remove the emissions system and put on a new Weber carb. any info would be greatly appreciated.
ANSWER: At the back of the tacho you will find 4 wires. The Green one is the power supply to the tacho. The White/Black wire goes to the negative terminal of the ignition coil. The Red/White wire is the internal illumination, and there should be a black wire with a ring terminal attached underneath one of the two thumb nuts that hold the instrument to the back of the dashboard. This is the earth wire.
o Forgetting to re-attach the earth wire is the most common fault.
o If the instrument illuminates when you turn the sidelights on, then this proves that the earth is OK.
o Test the Green power supply with a volt meter. It should be about 13 volts with the ignition switched on.
o Test the White/Black wire for continuity. I would disconnect it from the instrument and check it with an ohm meter.
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Fitting a Weber carb to an MGB is fairly straightforward. Moss Motors sell a complete kit with full fitting instructions. Personally, I prefer the 45DCOE sidedraft kit rather than the downdraft, but if you have a LHD vehicle then the downdraft may be your only option because of the position of the steering column.
Go to this link for more details:
http://www.mossmotors.com/Browse/PlateMenuProducts.aspx?WebCatalogID=8&PlateType
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QUESTION: Barrie this is David with the 1977 mgb You recommended a Weber 45DCOE carb
do you think a Weber 45mchh carb would work also do you think i would need
a fuel pressure regulator for either set up
Thanks,David
AnswerHi David.
Please check with Moss. Will their kit fit a LHD car? Is the standard AUF300 pump adequate for this setup, or should you uprate to a Facet pump and a regulator? I am in the UK so I don't regularly communicate with Moss Motors USA, and the UK arm of Moss deals mainly with RHD cars.
In my opinion, the original SU pump is perfectly adequate for fast road use, but not for racing. The AUF300 pump is rated at 18 gallons per hour and 3.5 psi pressure.
At 100 mph your car will probably do about 20 mpg. So it needs 5 gallons per hour. The AUF300 is rated at 18 gallons per hour, which is more than enough for your needs. I use one in my 3.5 litre V8 and it works fine at 125 mph.
The standard 45DCOE requires a maximum of 4.5 psi or else there is a risk of flooding. If you fit a Facet pump, then it will produce at least 6 psi so you then need a regulator.
If you want to fit a 45MCHH then I suggest that you read this thread from the Moss website:
http://www.mossmotors.com/forum/forums/thread/10845.aspx
Hope this helps.
