My buddy has a 455 that just wont stay running. You turn the key and it will fire but it wont start up. Then when it does start up it only stays running for about a minute and then dies. We have replaced the distributor and starter solenoid. We set the timing to top dead center and the firing order is correct. What are we missing here? Its an HEI Distributor too. Any help would be greatly appreciated. And Throwing the motor away and buying a chevy isnt gonna happen. (I already tried that one). Thanks in advance.