You can normally tell by just looking at the cam cover and its width, whether it houses 2 cams or 1, if you know what I mean.

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To the best of my knowledge If its an sr then it's most likely an 8 valve, the 16 valve doesnt say sr on the cover, and the 8 valve does. The 8 valve also has a an airbox whereas the 6 valve houses the air filter in the engine cover. Hth