Welcome to our Site for MG, Triumph and Austin-Healey Car Information.


MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGA - MGB Water Pump/Engine in MGA

I am in the process of fitting my newly rebuilt B 3 bearing engine in my 1500 A and hit a bit of an issue about the water pump which I have now solved (hopefully!).

My relatively new A pump would not fit the B block. The B block uses the same bolt fixings but it also has a locating dowel set into the block. I then purchased a new early B pump from Moss but I couldn't use that easily either for 2 reasons. The first reason is that although the A pulley would fit the belt was out of line with the pulley on the crankshaft, this problem could almost certainly have been fixed by buying the B pulley to match the B pump. The second reason was that the body of the pump protruded about 13mm further forward hence once fan fitted fouling the radiator, this problem could probably have been solved by moving the radiator forward but this has other potential issues. Being a very longterm A owner I have a memory that someone once told me you had move the radiator forward to fit an B engine to an A hence I guess this is where this came from.

As well as the difference of the dowel in the block and the hole to accommodate it in the pump casting the block casting is somewhat different in detail, the A one has a sort of flange as part of the casting that is missing from the B one. Also the B impeller goes slightly further into the block and the B pump body lacks a raised area to match the flange present on the A block. This is very esoteric and I suspect the B set up is an improved version but functionally in only a minor way.

For now I have solved my problem by slightly filling the body of my A pump so it doesn't foul the dowel in the B block and hence fits fine.

If anyone is interested in more details I took photos (1MB) of both pumps and blocks I can email (Barney?).


P M Dean

Very cool. Please send me the photos. (click on my email address).
Barney Gaylord

Oops, no hot link. Try this one.
Barney Gaylord

Can you send me that to....Ive been running my car with the mgb engine with the mods you didnt do.

Its funny that I did a lot off the trick mods I read from this site 15 years ago...but as time goes by
I almost forget whats been done for changes.

Anyway heres my email address:
Steven Devine

Barney, and Steven, now have the photos.

To clarify the engines are a 1500 A engine, obviously the used one in the photos, and a 3 bearing MGB one which is clean in the photos. The obviously used pump is a 1500 pump that I got from Moss around 4 years ago, and the new one is a GWP115 just purchased from Moss which is the correct version for a 3 bearing B.

Since writing my first email I filled up with water and it dripped back out at the bottom the pump. In fitting the A pump to the B engine I had used the A gasket trimmed to avoid the dowel and this didn't provide a seal. It was OK once I fitted the B gasket. Comparing the 2 gaskets and the larger recess in the B block it was clear why I needed to use the B gasket.

The car has now been road tested and all went well.

A final thought. Obviously there was a reason for this redesign for the B block. The effective depth of the B impeller is about 25% more than the A one hence presumably it is a better set up.

I have attached one of the photos which shows both pumps clearly showing the differences in impellers and also the additional smaller hole for the dowel in the B pump.


P M Dean

The cooling effectiveness of the MGA impeller will be less, so only do this if you can't obtain a proper MGB pump. You don't need to space the radiator very far forward to clear the B pump.
Bill Spohn

Just to close this item that I started I took Bill's advice and fitted the B pump. I had to move the radiator forward about an inch hence cut a bit off the shelf. Cooling seems fine so far.

P M Dean

This thread was discussed between 28/02/2014 and 16/05/2014

MG MGA index

This thread is from the archives. Join the live MG MGA BBS now