3 replies to this topic

[VinDiesel]

Hi

 

Any advise on how to determine what head I would have on my engine and what size the engine will be?

[IainStallard]

If it's a standard engine with the original colour, yellow was 998 and red is 1275.

998 engines have tappet chests on the back of the engine with a single breater coming up on the radiator side of the engine.

The cylinder head will have a casting number stamped on it under the rocker cover. 12G940 is 1275 however I'm not sure of the other casting numbers

[miniman24]

CAM4810 is the standard later 998 head, 12G295 the 998 Cooper head (used with raised D pistons) 12G206 is the same as 12G295, just earlier, 12G202 is either a 997 Cooper head or an 1100 head, or both There are also some earlier 998 heads (I think) that begin with J, not sure of the rest of the numbers. Theyre the main ones I can remember other than the 12G940 mentioned above :)

[Cooperman]

Let's do a bit of a definitive guide to engine identification here.

 

First of all look at the back of the cylinder block to see if the block has two rectangular apertures about 7" x 3" covered by panels with a centre 1/2" AF bolt.

 

If it has those apertures, which give access to the cam followers then the engine is either:

 

1.  A Cooper 'S' 970, 1071 or 1275

2.  An 850, 997, 998 or 1098

 

If it is an 'S' unit it will have 10 tapped head stud holes and one head bolt tapped hole in the top deck of the block. A non-'S' block has 9 tapped stud holes in the block deck.

 

If it doesn't have the apertures it is a 1275 non 'S' block, either A or A+ (more on this below).

 

Once the type has been identified the actual capacity can be ascertained by measuring the stroke length.

 

850 has a 2.687" stroke

997 has a 3.200" stroke

998 has a 3.000" stroke

1098 has a 3.296" stroke

 

 

970 'S' has a 2.4375" stroke

1071 'S' has a 2.687" stroke

1275 'S' has a 3.200" stroke

 

All other 1275 engines have a 3.200" stroke.

 

The pre-A-Plus 998 and 1275 blocks had a fairly smooth front surface on the side where the distributor mounts, whereas the A+ had cast-in webs to add crankcase stiffness. The A+ has a smaller distributor hole and a 3/8" UNF distributor clamp plate hole towards the front. On the A+ block the alternator bracket holes are nearer the front than on the original A-series block which had a dynamo.

 

With regard to heads there are a lot of options.

 

Any head with the casting number 12G940 is for a 1275, although there are different versions with different valve sizes and different combustion chamber sizes.

A 12G163 is an early Cooper 'S' head

 

The 997 & 998 Coopers and the Morris/MG/Austin 1100 had 12G202, 12G 206 or 12G295 heads.

 

That should enable any engine to be identified as a start. Of course, there are lots of camshaft options, etc.

 

I hope this helps.