At 07:59 PM 8/30/2001 -0600, Dave Quirt wrote:
>....
>The 18V is no different to install in a MGA than any of the 18Gx engines.
Well right up front (so to speak) you need the early engine front plate to
get the early engine mounts installed.
>.... the later 18V engines .... in a MGA. .... If one doesn't mind more
marginal cooling, one can use the MGA water pump on the B motor for rad
clearance.
Say What? The water pump on the 18V engine is considerably different than
the earlier ones. We on the list went through that discussion in mid
winter '96-'97 after someone suggested it might be possible to use the pump
from the 5-main engine in the 3-main engine for better cooling. NO WAY!
There was even an article in MGA! magazine from NAMGAR some years earlier,
of which I still have a copy, showing how to modify a water pump from a
5-main engine, ostensibly to be used with a 3-main engine. STILL NO WAY!
The mod called for shaving a fraction of an inch off the front of the
pulley mounting flange, presumably to set the pulley back a bit to help the
fan clear the radiator rather than shimming the radiator forward. The
whole concept was bogus, because the 5-main engine water pump cannot be
bolted to the 3-main block. I contacted the tech editor for NAMGAR. His
response was that he published that article as submitted by a member, not
having checked out the concept himself.
So finally in January of '97 a few list members conspired to nominate me
for the investigation, and eventually sent me a few water pumps of various
configurations for measurements and report. The report is that the
impeller on the 5-main engine water pump is larger in diameter (but the
same thickness) and located on a different center of rotation than the
earlier units, although the bolt pattern is the same. To use the later
pump on the earlier engine would require an inordinate amount of tricky
machining to create the geometry of the later snail chamber in the front of
the earlier block. On the flip side of the equation, installing a water
pump from any 3-main engine in the later 18V block would severely affect
the pumping ability. This would not just revert to the pumping volume of
the earlier setup, but the thing might not pump much coolant at all,
because the impeller diameter is much smaller than the mating snail chamber
in the 18V block.
The ultimate conclusion is that for the 18V engine you have to use a water
pump from a 5-main bearing engine (includes 18GB-18GK engines), and cannot
use one from any 3-main engine. This leaves a choice of three different
MGB water pumps with various nose end protrusion length. The early 5-main
pumps were long nosed (no go in the MGA) and the later ones shorter, with
at least 5 different water pump pulleys being used from '65 to '80. The
combination you need to install the 18V engine in the MGA is one of the
short nose water pumps from the 18V engine, and the pulley that goes with
it to make the belt groove line up properly.
Notes from past correspondence follow below (between the ------ lines):
--------------------
MGA and MGB water pumps from 1956-1964 engines, 1500 thru 1800 3-main 18GA,
have an impeller diameter of 2-3/8".
MGB 5-main engines from 1972 on (18V engines) have a water pump impeller
diameter of 2-7/8", and won't bolt up to a 3-main block. I believe this is
the same for the 18GB-18GK engines '65-'71.
The MGB 3-main engine water pump is nearly identical to the MGA water pump
and will fit the MGA engine without modification. It also has the same
water chamber and impeller dimensions and therefore has no advantage (or
disadvantage) in pumping volume. The impeller is 2-3/8" diameter. This
clearly implies that the MGA water pump will also fit the MGB 3-main
engine, and my book says the MGA pump is a lot cheaper. [More recently I
have come to have a distinct dislike for the aluminum bodied replacement
water pumps for the MGA, as the castings are weak and have a habit of
breaking where the generator attaches to the pump.]
The MGB 5-main engine water pumps all have 2-7/8" diameter impellers,
therefore will not mount up to a 3-main block without some serious
machining to the block. The cavity at the front of the block has a snail
chamber (ie. Archimedes spiral) surrounding the impeller. The cavity on
the 3-main block would have to be machined to duplicate the cavity on the
5-main block. To make that job even more difficult, the 5-main water pump
shaft is in a different location, a bit lower and a bit closer to the pump
inlet, so the larger impeller still clears the mounting screws.
The following is the distance from the back of the mounting flange (surface
that bolts to the block) to front of the pulley flange (surface that the
fan bolts to) for the pumps that I have (or had) on hand.
MGA 3-3/4" 3-main
MGB 3-3/4" 3-main 18G-18GA
MGB 4-1/8" 5-main 18GB-18GK
MGB (n/a) 5-main Early 18V '72-'74
MGB 3-1/4" 5-main Late 18V '75-'80
--------------------
I believe the pump from the 18GB-18GK engines is the one someone was
suggesting to modify (by cutting back the front flange) to work with the
MGA. I also believe this would only work for installing the 5-main engine
in the MGA, but would never fit into a 3-main block.
My other recollection is that the pump from the early 18V '72-'74 is the
one that is much longer, so definitely a no-go for the MGA. And I think
the trick for using either the early or late 5-main pump in the MGA is to
use the correct pulley to make the belt groove line up properly, although
the '75-'80 pump might be used with the MGA or 3-main MGB pulley and a 1/2"
spacer block.
Glad to share that which we collectively and so diligently conspired to
research. Kudos to the list as a whole.
Regards,
Barney Gaylord
1958 MGA with an attitude
http://www.ntsource.com/~barneymg
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