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MGBGTV8
wiring diagram
Ian Ailes asked "do you know if BL ever issued a revised
wiring diagram for the MGBGTV8? In the MGBGTV8 Workshop Manual
Supplement it was never revised to my knowledge".
Following the checks alongside made by Victor Smith, Ian responded
"I have had a look at both diagrams. I think the earlier
diagram in the V8 Supplement is likely to be closer to that
used in the later rubber bumper models in 1976 than the later
diagram in the MGBGT manual. For example, the wires to the
coil are slightly different. The drawing number is 3NB 034
against the later drawing 7NB 007".
Inline fuse protection for the V8 overdrive
With a Laycock overdrive, there is a surge current when the
overdrive solenoid is switched on. Barrie Jones says “the
initial
current is about 16 amps but once latched, the holding current
is only 3 amps.” The fuse
rating needs to be sufficient to cope with that surge current
so Barrie recommends a 20 amp slow-blow fuse. The simple upgrade
of fitting a blade fuse is described in V8NOTE460. Link
Blade
fuses from B&G. Link
Posted: 260904
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What
wiring diagrams are there seen in the workshop manuals?
.
MGBGTV8 Workshop Manual Supplement (Part No AKD8468) dated
"BL 1973"
In this manual you can see on page 86.00.01 there is a wiring
diagram and on the facing page 86.00.02 there is a key to the
numbered parts on the wiring diagram.
MGB
Workshop Manual (Part No AKD3259 15th Edition) dated "Copyright
BL UK 1976"
I see there are a number of wiring diagrams in the manual
ending with Diagram 19 on page Nb.22 (MGB. Issue 1. 86842).
See photos
of each wiring diagram and list of parts seen in the two manuals.
Link
Manuals for the MGBGTV8 model. Link
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Comments
on the MGBGTV8 wiring from the late Peter
Neal
Victor Smith had heard some MGBGTV8 owners have had a short
which could cause a fire because the wire to the overdrive solenoid
can get trapped between the gearbox and the tunnel cutting through
the wire or, if you are unlucky, shorting out the loom and burning
out the main harness.
When I was preparing V8NOTE460 describing the modest upgrade
of adding a blade fuse in the overdrive circuit, I called Peter
Neal (Club Archivist and former employee at the MG Plant at
Abingdon) to see if he knew whether a fuse had been considered
necessary when the cars were being produced. He was involved
in auto-electrics there and mentioned how the development and
production of the MGBGTV8 was an extraordinarily low budget
project. He said “there were several cases where additions
to the loom and wiring would have been desirable but the cost
pressures were real, they simply had to keep both development
expenditures and production costs for amended components for
the V8 to a minimum.”
Peter said "the lack of an inline fuse on the ignition
power feed to the overdrive switch on an MGB and its derivatives
is something that has always been seen as a significant oversight
in terms of protecting the wiring from a burn out should a short
develop".
Sadly Peter Neal passed away in 2026.
Peter Neal obit. Link |
