I started my engine assembly this weekend and everything was going well until I went to install the pistons and rods in the block. I haven't gotten to cylinders 1 and 2 yet, but the rods in cylinder 3 and 4 are touching the block at the bottom of the bore next to the oil passage. I've seen people talking about grinding the block on 63 strokers, but from what I can tell most people are hitting the block on the side without the oil passage.

Is it safe for me to try and grind the block? How much meat do I have there before I hit the oil passage?

6-bolt 4g64 bored to 87mm
stock 100mm 4g64 Crank
156mm rods
87mm 4g64/63 Pistons (1.13 Compression Height)

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I'm not 100% sure about how much material is there to grind, I don't know much about the 4g64, but it strikes me as odd that you have 156mm rods. Are you running a heightend pin piston?

Yes I am, sorry I meant 1.13" compression height pistons.

I am aiming for a 4g64 long rod like mentioned in the attached engine list from Magnus.

Well I went ahead and grinded it a little bit and sure enough the rod cleared. I put the pistons in cylinders 1 and 2 and they hit on the same side and barely touch on the other side. So I went ahead and grinded both sides of all the cylinders. Everything rotates very nicely now.

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I ground through on my 4g64 block. Took a lot of grinding so there is some material to remove there if need be. I had to install a stainless steel tube in the oil passage and drill holes from all the mains and the head. Block still works fine.