Trevor. You’re right about the timing chain. Any serious thoughts about raising the camshaft in the Y forces the chain issue to be considered before all else. Other than this, raising the camshaft in the block sounds relatively simple but ultimately ends up creating some issues in regards to the lifter angles if these are not compensated for. Simply raising the camshaft and not relocating the lifter bores increases the lobe centerline for a given camshaft.
On the Y, there is only 0.080” to 0.130” of lifter clearance to install the camshaft with the lifters placed at the top of their bores. Core shift during casting typically has each bank of lifters sitting with different clearances to the camshaft so this has to also be taken into account. Machining the bottom of the lifter bores so the lifter can be raised only compounds the problem in that the lifter bore itself now becomes even shorter. Relocating the lifter bores so that the camshafts intended lobe centerline angle remains the same when raising the camshaft gives a net gain of zero. With the stock camshaft journal sizes, the camshaft base circle still ends up being the limiting factor in getting more cam lobe lift while using the stock lifters. Going to a non mushroom lifter design gets around most of this.
Lorena, Texas (South of Waco)