Barney Gaylord wrote:
> Third, you need to use the MGA clutch disk, as it has to match the
> splines on the gearbox input shaft. This is much easier than changing
> the input shaft to match the MGB disk.
Agreed ... but the 23 spline input shaft from a 'B' 3-synchro tranny can
be fitted to the 'A' tranny.
> Fourth, since the MGB pressure plate is thinner than the MGA
> pressure plate, you need all the rest of the MGB parts in front of
> the face of the gearbox. You will need to obtain from a 3-syncro
> MGB gearbox, the gearbox front cover (pivot point is different and
> has a nice rubber seal) ...
MOWOG part number 22B55 AB
>... the MGB clutch release arm ...
MOWOG part number 22B57A
> Fifth, the MGB 5-main clutch pilot bushing (spigot bushing) in the
> rear end of the engine crankshaft is larger than the bushing in the
> MGA & MGB 3-main engines, both ID and OD. The MGA and
> 3-main MGB bushing is 5/8" ID. I do not recall the OD of the 5-main
> bushing (anybody?). The solution here is to go to your local bearing
> supply house and obtain a bronze bushing ....
Or obtain the 'B' spigot bush (pilot bearing) for the 3-main to 5-main
conversion from Moss (Part # 330-570) ... if the input shaft from a 'B'
3-synchro/5-main tranny if used then this is not an issue as it will be
of the correct diameter and allow the use of the 'B' 5-main spigot bush.
Since you need the cover plate and release bearing arm ... it makes
some since to pick up a donor 'B' 3-synchro/5-main tranny ... then you
will get the input shaft and all of the internal bits (they are identical to
those found in the 'A' tranny).
> Sixth, the MGA 1600 has a high starter position similar to the MGB.
> The MGA 1500 has a low starter position. You will need to use the
> engine rear plate from the MGA to match the MGA gearbox.
Yep ... the 'A' engine plate needs to be machined to accept the 'B'
5-main rear engine seal ... simple process of enlarging the the hole in
the plate.
> You may be able to use the engine rear plate from a 3-main MGB
> engine with the MGA 1600 gearbox, just a guess, can anyone else
> comment on this?
Nope ... the 3-main 'B' engine plate will not bolt up to the any of the
'A' trannys.
> Eighth, the MGB 5-main engine does not have a mechanical tachometer
> drive. So you need an electric tach. And, to keep appearances in order,
> You want to obtain the electric tach from the same model MGB as the
> aforementioned flywheel, 1965-1967.
*Rumor* has it that the 'B' 5-main block could be machined to accept the
'A' mechanical tach drive ... but that depends on whether or not you are
going to rebuild the 'B' engine and will require that the tach drive be fitted
to the cam ... I haven't tried this ... yet ... ;^)
> Ninth, you need to use the water pump from a 5-main engine, and it
> should be the short nose pump, I believe also from the 1965-1967 MGB
> engine, but someone may jump in here if I err.
I haven't been able to measure all of the pumps, but from what I've been
able to determine the 3-main pumps ('A' & 'B') are ~ 3-1/2" deep, the early
'B' 5-main pumps ('65 -74) are ~ 4" deep, and the late 'B' 5-main pumps
('74 1/2 - '80) are ~ 3-1/2" deep ... as Barney stated "somone may jump
in if I err", but it looks like a 'rubber bumper' pump would prevent any
possible clearance problems.
> Tenth, you need to use the water outlet elbow (thermostat cover) from
> the MGA or MGB 1956-1967.
I think any chrome bumper elbow will work, but from '68 -'74 (North
American spec) it would have the bracket for the air pump ... besides
the early aluminum elbow polishes up *real nice* ... ;^)
> ... so I'd advise converting any post 1967 engine to pre 1968 emission
> standards.
Agreed ...
> Thirteenth, you can use the MGA exhaust manifold and the rest of the
> MGA exhaust system in its entirety. Some people say that the MGA
> exhaust system un dually restricts the performance of the larger
> displacement MGB engine. But, it will run just fine with this setup, the
> drive ability will also be just fine, and since you're going from 1500 or
> 1600 cc to 1800 cc, you will be getting a substantial performance gain,
> and will likely not be concerned with the small loss caused by the MGA
> exhaust system.
In theory ... the smaller diameter 3 to 1 MGA header so provide better
low in torque, but the top end will suffer.
> Fourteenth, If you do want to use the MGB exhaust manifold in the
> MGA, be aware that it may hit the steering column. The fix for this is
> to mill a slight angle on the face of the manifold where it mounts to the
> cylinder head, something like 1-1/2 degrees as I recall (but that may
> not be quite right), in order to move the bottom end of the exhaust
> manifold a little towards the engine. You will also need to have a new
> front pipe formed to adapt the MGB header to the MGA exhaust.
Rumor ... you can fit the stock 'B' header by shimming the LH motor
mount to cant the engine away from the steering shaft.
The stock 'B' manifold is actually quite efficient and its LCB style appears
to have been carried over from the MGA Twin Cam ('Twinkie') header ... if
I am reading the 'Orginial MGA' correctly, the 'Twinkie' has a larger diameter
exhaust like the 'B'. It just might be possible to fit a 'Twinkie' exhaust
to the stock 'B' header ... to confirm this I need the cooperation of a
'Twinkie' owner to determine the diameter of the down pipes, the distance
(centerline to centerline) between the two down pipes, and how far the
'Twinkie' header travels down the side of the block (from the centerline
of the exhaust port to the bottom flange(s).
Safety Fast! ... larry.g.unger@lmco.com
'61 MGA 1600 MkII
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