VALVE EX 1275 MK1 CO S 1.219″

Exhaust valve. 1.22″ (31mm) x 3.52″
As it is possible, even common, to swap one head for another on 1275 engines, it is quite easy to become confused, or worse yet, confuse the parts-guy when it is time to order new valves! Be aware that if the head has been worked on previously, it may have oversize valves; it may have undersize if seats have been installed. Unless you are 100% sure what is in your cylinder head, it is a good idea to remove a valve for accurate measurement. There are two valve lengths used (nominally 3.52″ & 3.57″) and three different style of collets, (wide, narrow, and three-groove) there is also more than one different head diameter! Note that 12G1316 (Smog-Type), all variations of the 12G940, and the latest CAM head castings all use the following 3.57″ long valves. Early Cooper S valves If your 970, 1071, or early 1275 Cooper S still has the original AEG163 head casting, you must use short, 3.52″ valves.