I was running the engine on my 87 900 S 16v non-turbo with 133,600 miles and I heard a clicking sound in the engine. I checked all the fluids in the engine and everythings good. There doesn't seem to be a loss in performance in the car, power is the same and it runs good, except this sound. Is this normal? None of my other cars had a sound like this, then again all my other cars were OHVs and not DOHCs. Thanks for any info.