The difference between an 840 and a 291 head is?
Someone just sent me one of each and said they came from the same car. They told me they were both 840's and then I get this 921. I looked around and on one site it said the chamber was 1 cc different. On another it said they were the same. Does anyone know what the difference between these are? I can't see how they even look different...help please
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