Crap. I bought the same heads from a reputable shop a year and a half ago. I had them immediately checked out. The seats and guides were spot on. I then had the shop machine the guides for a higher lift cam. I have started porting them as well. Prompted by this topic I fit a Magnum intake gasket to mine and have the same results as the poster here. This sucks. I planned to run either a Weiand TR or an Offenhauser dual quad intake so having a Magnum head with the LA intake bolt arrangement is crucial.
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