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The 1/2" headstuds in DEs was the fix until the L19/CA625 made them obsolete and unnecessary hassle. The original ARP2000 material had very low torque specification and was causing headgasket failures in the 500s and 600s. People moved to 1/2" studs (including myself), and the ARP2000 material in that size we could torque to 90-105 or so, and this fixed the issues. Eventually ARP released L19 in stock thread size, and then you could build a DE with adequate clamping load on the headgaskets without the extra hassle of machining for 1/2 studs.

The blocks showed no signs of issues with oversizing for the studs. My block was tapped 9/16 then had thread inserts down to 1/2". The "machine work" for the oversizing was done with a hand drill, and the studs were so crooked that you couldnt install the heads with the studs threaded in (not my work, sent it to a member that allegedly arranged a group batch of this with a machine shop, found out when I got it back that he was doing them by hand), you had to set the head on the gaskets and then thread the studs in. That engine then lasted over 10 years without headgasket failure 600-800hp. Once it was taken to over 900whp, it didnt last much longer... although it was the old fatigued crankshaft which failed and took out the engine.

In summary, the DE 1/2" headstud debacle fixed the issue with blowing headgaskets at 500-600hp. It was made obsolete by the L19s and then CA625+. There is no evidence that a 1/2" headstud would do us any good for what is happening now, which doesnt appear to be a clamping issue, but a cylinder movement/support issue.

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