Roller cam tools
Having worked at a foundry I believe the first pour from a ladle has less slag because it is easy to hold back while tipping the ladle. Also the first molds to be poured are scrutinized more by QC.
If you go to old school engine builders they always want 340-1's for their race cars
If you look closely at this X block which is a 318-11 "340 race block" the right rear lifter bore had to be filled with weld it was totally missing a chunk from the forge. Also the cylinders were out of concentric and could only be bored 4.080 safely. I had X blocks bored 4.125 and more some 4.200 with out a problem. Not this high core number.
Usually High core numbers when they let go they take out the whole cylinder. I had them come in with just the head studs hanging from the head. The rod did not break the cylinder just came apart at high rpms coming off the turn.
If you are going to make serious HP I would avoid using a high core number.
What I have found over the years is motors with a lower core number such as 340-1 and 340 -2 have a real clean casting.
Having worked at a foundry I believe the first pour from a ladle has less slag because it is easy to hold back while tipping the ladle. Also the first molds to be poured are scrutinized more by QC.
If you go to old school engine builders they always want 340-1's for their race cars
If you look closely at this X block which is a 318-11 "340 race block" the right rear lifter bore had to be filled with weld it was totally missing a chunk from the forge. Also the cylinders were out of concentric and could only be bored 4.080 safely. I had X blocks bored 4.125 and more some 4.200 with out a problem. Not this high core number.
Usually High core numbers when they let go they take out the whole cylinder. I had them come in with just the head studs hanging from the head. The rod did not break the cylinder just came apart at high rpms coming off the turn.
If you are going to make serious HP I would avoid using a high core number.