Dear Barney,
Apologies for the length.
I'm very new to this list and just picked up on this thread in which I read
your post with interest and a sickening nostalgia.
I have not had an an MGA, but used to own an MGB with the 3 bearing 18GA
motor (I believe it is very similar to the 1600 MGA). I rebuilt this motor
and started to have a fun time (after proper running in) 'thrashing' the
car. I was horified when less than 5000 miles after the rebuild at just over
6500 rpm the oil pressure died as did the motor when it shredded and threw a
main bearing!
This was twelve years ago when I was young and very green to modifing and
tuning LBCs. After this experience (and the pitying smiles of more
experienced MG owners who heard of it) I bought the MGB Special Tuning
booklet, Publication Part No. C-AKD 4034 D, 1967. This booklet has a lot to
say about oil surges and how to overcome them on the 18G and subsequent
motors. I feel confident that if the following mods are applicable to the
MGA, and you apply them, then you won't have any further problems.
I will quote the relevant excerpts and I suggest you investigate the sump
and pump modifcations. All the 'experts' that I spoke to said these were
essential for any continuous high rpm work from the motor.
P37: Engine oil sump
"Especially in long distance racing, the oil level may drop to a
position where oil surge on violent cornering and braking may cause a
temporary but complete loss of oil pressure. This could be seriously
detrimental to the engine and may result in bearing failure. It is advisable
to increase the oil capacity above the oil pump inlet and to fit a baffle in
the oil sump to prevent the oil surging away from the pump inlet. This can
be done by fitting the deep sump or altering your own sump by cutting
through approximately 1&1/4 in. (31.7 mm) from the bottom and gas welding in
a 1 in. (25.4 mm) distance piece of sheet metal, or obtaining another sump
and cutting off 2&1/4 in. (57.4 mm) from the bottom and welding this to the
top of your sump for the 18G/18GA engine.
"Make up and spot weld the surge baffle to the inside of the oil
sump as illustrated in Figs. 5 and 6. [good clear drawings, but alas I have
no scanner]
"Larger sumps already modified are available (Part No. C-AHH 7252)
for the 18G/18GA engine.
"Fit the correct packing piece between the pump strainer and the
pump extension for 18G/18GA (Part No. C-AHH 7238) using an extra gasket and
longer bolts. This will lower the oil pick-up to the correct position
"Weld an extension piece onto the end of your dip-stick so that the
original oil level is maintained, or use the stick as it is, and make a new
maximum high level mark 1 or 1&1/4 in. (25.4 or 31.8 mm) above the existing one.
"For short circuits, where oil levels may not drop, the standard
depth of sump should be found satisfactory, but the surge baffle should be
made up and fitted as illustrated."
P41: Oil pump
"Sometimes the oil pressure increases up to, say, 5500 rpm and drops
off in pressure beyond this speed. This can be prevented by machining the
pump cover and making twin inlet ports to the pump. (See Fig. 7 for machining.)
"A point which should be carefully checked is the oil pump strainer.
The threaded attachment plate is spot welded to the inside face of the
strainer top plate. If the strainer top plate is not flat, or if the
attachment plate has not pulled up perfectly to the underside of the top
plate, an air leak can occur between the attachment plate and the top plate.
Ensure that the top plate is flat over the gasket area, and to make sure
that no air leak can occur carefully warm the whole strainer up and tin
around the hole in the top plate to the attachment plate so that the bottom
corner joint is sealed. Under normal conditions this position is under oil
level, but when oil surge occurs, as in competition work, it may become
uncovered."
Other suggestions to enhance oil flow include machining the opening in the
top casting of the oil filter bowl, fitting a larger oil cooler, and
increasing oil pressure through uprated oil relief valve springs.
I hope all this helps and apologies again for such length.
BTW I still have various MGB bits and pieces that I could sell to the right
buyer, such as, reclining seats, banjo diff, front X member and suspension,
wire wheels, weber manifold, BL grill, boot lid, headers, many more too
numerous to name.
For the discerning MGA owner I also have an immaculate original MGA Workshop
Manual part No. AKD600C (yellow vinyl 4 D ring binder, pages complete and
unmarked) and Kenneth Ullyett's 1960 publication: The MG Companion, which
covers the history of MG up to the A series and includes tuning info.
I now own a TR7 Sprint (no flames please) and would be most willing to trade
parts as the lovely little wedge needs some serious surgery which is forcing
me to dispose of some of my MG treasures. ;-)
Owen Michaels-Hardy, Sydney Australia
1980 TR7 Sprint 16 valve FHC
|