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Dunno this engine itself, but if like many/most 'HO' engines, the static compression ratio of the HO is higher than the standard. The octane difference indicates that. Whether the pistons make the CR higher or the heads, IDK. If the pistons are different, then you'll just have lower static CR and less 'juice'.

Hard to hear detonation of you have a helmet on....not any surprise.
 

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HO pistons are flat top and standard are dome top. My worry is that I will raise the compression even higher than HO due to the dome top piston.
OK understood. Sounds like the dome on the standard pistons partially makes up for compression loss with a more open head chamber. Really hard to know what you actually have without compression heights and dome volumes from the 2 pistons and the head chamber volumes, but like DenonO and you have said, you may end up with high CR's.
 

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LOL.... I never would have thought about asking about re-using it. How do you 'clean up' the 'chewing' that those bits if ring did on the head surface? The raised edges and peaks that will be come hot and can promote detonation. Did they promise how long 'It'll be OK.'?
 

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I have no idea about the shop there.... but such a statement on that head condition is not confidence inspiring to me. I am sure that some folks have thrown such parts back on and run it and maybe it lasted, maybe it didn't. But poor parts usually results in poor durability.

Hard to say what 'cleaning up' did to volume in the head and changing/lowering compression ratio. I can understand needing to be economical to some extent, but I'd be making it right, just to get the jagged/rough surfaces out if nothing else. There is not as much margin to failure in these engines compared to automotive engines.
 
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