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MG MGA - MGB head on MGA 1500 engine?

Can a Stage 2 MGB cylinder head be used on a 1500 engine? Or will it be a problem with valve size or combustion chamber volume or anything else?

Not my car, I´m asking on behalf of an MG friend.

Tore
Tore

Depends on the year of the MGB head and whether it has been skimmed or not - early ones with the deep combustion chambers can be used as is - later 18V heads and early ones that have been skimmed will need the relief cut out for the exhaust valves machined into the top of the bores.

Very late 18V heads also have an offset oil feed for the rear rocker post - this must be matched to the correct rear post.

Otherwise they are a straight swap.
Chris at Octarine Services

Thanks, Chris.

Tore
Tore

Using large chamber heads on an MGA 1500 can get you lower than 8:1 compression. Not exactly a performance mod!
Bill Spohn

Unless of course you are bolting a supercharger on the side ...
Chris at Octarine Services

I recently raised a similar query and I had a response from Barney which basically made the same points as Chris and Bill.

It is a bit of a catch 22. As I understand it if you skim the head to keep the CR up you have to also machine the block, and if don't skim the block you gain power from the better head design but loose it due to the drop in CR.

As I also have the rest of the 3 bearing B engine I will wait until I do the full engine job. My 1500 engine is OK for now.

Paul
Paul Dean

The 3 main MGB and early 5 main had the same combustion chamber as the Mk 2 MGA. The MGA used flat top pistons, the MGB have a slight depression.

1500 and 1600 engines had a deeper concavity so as to match a smaller combustion chamber on the early small valve heads, which is why just slapping a later head on will drop your compression a lot.

If you built the engine with new flat tp pistons you'd be fine.

Just build the 3 main MGB engine - it makes a great engine for the MGA.
Bill Spohn

Bill,

Are these MGB pistons?

John


jbackman

Bill, they look very similar to my MGA 1500 pistons. I may be wrong.

Frank
F Camilleri

Just taken the head off my 1500 and they look the same.
Dave
Dave Swinburne

John

I have a 3 bearing MGB engine and a MGA 1500 both sitting my garage without heads. I can see the B piston well. The A engine is a bit buried although I can feel, and to some extent see, the piston tops and quite frankly they both very similar to your photo.

BUT they are certainly NOT B pistons as your photo is not of a B block. The gaps between bores on a B block are far less than on your photo .

Paul
Paul Dean

This thread was discussed between 25/06/2013 and 05/07/2013

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