The following is from Barney Gaylord of the MG list and can be reached
at: barneymg@mgaguru.com
Barney wrote:
Okay, I'll bite. I don't think this will make it to the Spritgets list,
because I'm not subscribed there. If anyone wants to forward it there,
it's okay.
To verify the engine block series look for 1-inch tall raised cast
numerals on the side of the block just above the left engine mount. It
WILL have 1500, 1600, 1622, or 1800 (or an odd exception labeled 1620).
MGA 1500 and 1600 both use the "15" head. MGA 1600-MK-II has the 1622
engine and uses the "16" head with one size larger valves, better
porting, and larger volume combusion chamber (43cc vs 38cc). The 1622
engine also has a stronger crankshaft which will not fit into the
1500/1600 block without some serious machining on the block. MGB has
the 1800 engine with "18" head. The "18" head is nearly identical to
the"16" head except for a small difference in the Weslake promentory
(pointed heart shape between the valves in the chamber).
Heads with no such series number on top at back could be almost anything
with any size valves. A lot of factory supplied replacement heads had
no series number there and could be machined for various size valves.
The only way to know for sure is to remove the head to measure the valve
head diameters. I do not have a full list of casting numbers to know
which "non-series-marked" head may have what size valves (because they
are not MGA parts).
The 1600 block was a special casting for MGA to compete in the 1600cc
racing class. The 1600 engine in similar form could have been used in
other "sporting" type cars such as TVR and Elva. When the factory
stepped away from racing they dropped the special (expensive) 1600 block
casting and went to using the 1622 engine, then giving it the "16" head
with larger valves to make more power. The "16" head is generally rare,
as it was only used for 14 months of MGA 1600-MK-II production. The
same engine as a whole may have been used in some sporting variants such
as TVR and Elva.
None of this necessarily applies to cars other than the MGA (and MGB).
I don't know if the "16" head was ever used on any other car, especially
not on "non-sporting" models. Very many other applications (vehicles
and stationary engines) using the 1622 engine had the "15" head.
The "1620" engine block was cast in Australia. This has the same bore
and stroke as the 1622 but uses the crankshaft from the 1500/1600 series
engines, NOT the crank from the 1622 engine. The 1620 engine also had
the "15" head and was used in some Morris Major cars. Some of these
engines appear to have found their way to England and are sometimes
discovered being used as a replacement in other cars.
The Nash Metropolitan had a lower power version of the Austin 1500
engine (in late production). The head on the Met 1500 engine has
smaller valves and is totally unsuitable for use on the MGA as it saps
away too much torque and power at anything over 2000 rpm. It is so bad
that you would have trouble entering an acelleration lane on an
expressway, and the engine would struggle to go much past 4500 rpm with
any appreciable torque. I had one of these small valve heads on an MGA
once, and it took a couple of miles to get it up to 70-75 mph.
Hope this explains a few things.
Barney Gaylord
1958 MGA with an attitude
http://MGAguru.com
<http://mgaguru.com/>
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