Roger wrote and Scott replied:
>> When fitting an engine from a later (Black bumper) MGB into a chrome
>> bumper car, will the later engine fit using the later mounts & brackets, or
>> does an earlier front engine plate have to be used, along with its brackets
>> and mounts?
>
>No problems. I have an 18V in The Green Car now, just waiting for some
>more time to get everything hooked up. That 18V was last used in a '65
>chassis, so I think we're covered there, modulo the known problems with
>gearbox/starter/etc. on the 3-main chassis.
74 1/2 on MGB's used those dinky, weak, unstable round motor mounts. The
mounting brackets are different; the front plate *is* different. Sorry, Roger.
>> 2) Transmission pilot bushing diameter is smaller on 3 main engines (And
>> maybe All 3 syncro trannys?)
>
>Yes -- all 3-synchro transmissions require a smaller pilot bushing than
>used on the 4-synchro transmissions (or, well, than used on the ENGINES
>that came attached to 4-synchro transmissions).
Nope, not quite. The 3 main engine takes a (much) smaller pilot bearing than
the 5 main. All 4 syncro boxs were behind 5 mains, and therefore have the 1"
pilot. 3 syncros can be either.
>> 3) Engine rear plate may need to be changed when changing between 3 and 3
>> syncro trannys. ????
>
>Yes, I think; the starters are either of different types or in
>different places. Check the floor pan shape on early vs. late
>to see what that looks like.
Yes, different starter, and the change was at same time as the change to 4
syncro. Early style used the infamous inertia bendix with remote solenoid.
Later style used the solenoid-engaged bendix, hence the solenoid was on the
starter.
How to tell the difference:
The 3 sycro back plate has the two starter holes inline vertically. Both
are through-holes. The 4 syncro has the holes canted top out. Bottom hole
is threaded 3/8-24; the bolt is behind the flywheel and so does not pass
through into the bellhousing.
>Uh-oh. That's news to me. I've got a '72 18V in my '71 chassis, and
>the engine mounts are the same on both. I'd assumed that the mounting
>brackets would be the same across all 18V lines.
>
>On the pre-18V motors, the motor mounts don't connect to the front plate
>directly, but they're held in with big cross-headed screws that run
>parallel to the crankshaft; there's an L-shaped bracket that gets the
>two bolts/studs sticking out of the rubber portion of the mount. Then
>there's a four-hole metal plate that gets bolted to the chassis. Is
>this not the case on post-75 Bs? I've never had occasion to look...
The black bumpered cars carry the mounts lower on the engine. The basic
idea is the same, except the mounting plates sit lower. In turn, the
front plate has the ears for the two cross-headed lower by about an inch.
The engine mounts themselves are very different. Round rubber blobs that
attach to the engine with two through bolts. The mounts have a single
3/8-24 stud that goes through the mount tangs on the body. These tangs
are even with the front frame rail, unlike the early cars that had the
pads well above the frame rails.
>> 7) Earlier engines don't have the mounts for alternators.
>
>Right, and I'm not sure when the changeover happened. Note also that
>the wiring harness changed between May 1971 and whenever my parts B was
>built in 1972; the connectors on The Green Car wouldn't fit the alternator
>that came from the parts car, so I refitted the (fortunately still sound)
>alternator from the Green Car originally.
MGB's got alternators in 71; that weird two plug one. In 72 they went to
the single plug 16ACR unit. That 71 alt you have is unique, you won't get
another one. Many years ago, Lucas included a late model plug with every
alternator for the purpose of retrofitting cars like yours. They no longer
do this. When you need to convert, you'll have to roll your own plug.
Randy
randy@taylor.wyvern.com
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