Thats basically what the timing card says. 286 (GOOD IDLE IN 2LT - INCREASED TOP END) 312 (COMPETITION - HOT STREET - ROUGH IDLE)
Sean had paired them up in a 2.2L High compression engine and I am attempting to do the same. I'm just not sure if he had used the 286 intake and 312 exhaust or 312 intake and 286 exhaust. The good old interwebs are full of opinions just not sure how much is fact. Some people are saying increasing the exdaust duration helps top end with less loss of bottom end than increasing intake duration. Others say it's old wives tales and you don't need longer exhaust duration and others say its engine dependant ie increase the exhaust duration to compensate for poor exhaust port design. I wish old Sean was still around. A great deal of twincam information was lost when he qualified for the eternal grand prix in the sky.
Glen
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