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MG MGA - Replacing 1500 Cyl. Head with a 1600 Cyl. Head

I am replacing a 1500 cylinder head on a 1500 engine block. I've been through the archives and have found "strings" discussing the use of a 1500 head on a 1600 block and a 1800 head on a 1500 block but no mention of a 1600 head on a 1500 block.

1. Will a 1600 cylinder head fit on a 1500 block?
3. Will I need to make ANY modifications? eg. intake or exhaust manifolds, water intake, valve cover...
2. Should I expect any performance issues/irregularities? eg. overheating, fuel consumption, etc.
gerard hutchinson

My memory is getting fuzzy but if I recall there is no 1600 head per say. The 1600 was an MG only thing throughout the corporation and used the latest 1500 head. Was not till the 1622 that the head was upgraded and marked with a 16. All heads interchange with some of the larger valved ones needing "eyebrows" cut into the block surface as the larger diameter valves can touch at the top edge of the smaller bore.I'm sure there will be others who can go into greater detail.
gary starr

1500 and 1600 engines use the same 15 head with 38cc chamber volume (and dished pistons). 1622 engine used the 16 head with 43cc chamber and one size larger valves (and flat top pistons). Early MGB 1800 engines used the 18 head, nearly identical to the 16 head. Only minor difference in the shape of the Weslake promontory (heart shape in the combustion chamber). The 18 head is a very good substitute for the 16 head.

Using a 16 or 18 head on a 1500/1600 engine would result in low compression ratio (about 7.5:1). You can shave the head from 3.187 to 3.140 thickness to reduce chamber from 43 to 38cc to have original CR of 8.3 for the 1500/1600 engines. The bock then requires eyebrows for valve lift clearance. Any time you shave a head more than 0.020" you should carefully measure clearance of the valves at full lift.

From 1968 on North American 18 heads had air injection ports. 1972-1974 MGB used the "L" head with one size larger yet intake valve and smaller (38cc) chamber volume. This one has shallower chamber, like it was pre-shaved at the factory, and it requires eyebrows in the block. 1975 on MGB used an 18 head (similar to 1968-1971) with 43cc chamber plus a water outlet at back on top for manifold water temperature control.

All Austin B -series heads are bolt-on physically interchangeable (except Twin Cam which has different head bolt pattern).

Ok Barney,

I have just a regular 1500 block...

Would a normal machine shop understand your last post? I certainly do not! HAHA!

What is an "eyebrow"?
What needs to be measured/shaved?
gerard hutchinson

Check my web site. Lots of information on cylinder heads and eyebrows.

This thread was discussed between 04/04/2018 and 06/04/2018

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