With the lift of a factory ra3 cam you will have no clearance issues, you should be safe up to. .420” lift which that cam does not have, at least with 1.5 rockers,.
Non the less you should still check your piston to valve clearance, and it might save you some time at first to do that without the head gaskets in place.
In terms of compression with the 62 castings, they are more like 75 CCs unless they have been milled and if they have had a valve job done to them that will make them more then 75 CCs.
What pistons are in your 389?
If they have more then 4 valve notches then they are more likely the source of your knock issue since they have a huge deck clearance!
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Last edited by 25stevem; 07-20-2022 at 04:41 PM.
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