Compression Calculator
I have KB 243's in my 340, they measured .018" over the deck (which is the spec with the stock deck height). The compression calculators I was using, including the Wallace calculator, had some issue dealing with the deck height and the piston volumes because of the way that piston is shaped. It looks flat but it actually has a .030" protrusion, so the shoulder of the piston sits .012" below the deck but the top is .018" over. I'm not entirely sure where the 6cc volume comes from that they advertise, but the tech I spoke to at KB straight up told me not to use it. Instead, he told me to use a deck height of 0 and a 7.3cc volume, with that volume accounting for the protrusion and the valve reliefs.
From the tech...
I ended up running a different head gasket than the one I gave the Tech and my head chambers ended up 1cc larger, so it calculated a little differently when I updated the gasket
Also, with the KB 243's if you do end up with the tops of the pistons .018" over the deck like they're supposed to be you'll need to check your piston to head clearance if you run closed chamber heads. You may need to adjust that clearance with a thicker head gasket. I run open chamber 308's on mine.
I have KB 243's in my 340, they measured .018" over the deck (which is the spec with the stock deck height). The compression calculators I was using, including the Wallace calculator, had some issue dealing with the deck height and the piston volumes because of the way that piston is shaped. It looks flat but it actually has a .030" protrusion, so the shoulder of the piston sits .012" below the deck but the top is .018" over. I'm not entirely sure where the 6cc volume comes from that they advertise, but the tech I spoke to at KB straight up told me not to use it. Instead, he told me to use a deck height of 0 and a 7.3cc volume, with that volume accounting for the protrusion and the valve reliefs.
From the tech...
I ended up running a different head gasket than the one I gave the Tech and my head chambers ended up 1cc larger, so it calculated a little differently when I updated the gasket
Also, with the KB 243's if you do end up with the tops of the pistons .018" over the deck like they're supposed to be you'll need to check your piston to head clearance if you run closed chamber heads. You may need to adjust that clearance with a thicker head gasket. I run open chamber 308's on mine.