Just so everybody thinks it all the way through. When you lengthen the stem, you also lengthen the installed length/height of the valve spring. So, make sure you have your valve springs tested and know at what installed height they need to be to deliver the correct LBs on the seat.
I frequently use Isky 185G springs on my high-performance builds and I take a steel Chevy valve retainer and cut it back for the 185G springs. The retainer is much thicker than the stock 49-53 ones, so it helps take up the longer spring distance of the 1.6 valves.
Also, when buying new 49-53 style valve guides, it is best to have the exhaust guides that do NOT have the intake seal groove cut into them. Why? Well, the more surface area on the valve guide OD, the better heat transfer from the exhaust valve into the block - this is important for valve cooling (exhaust side). You'll see a 'solid' type exhaust guide below.
I also make aluminum 'spacers' to put against the guide to set the final installed height. I don't like stacking up 3 or 4 .060 spring shims (I'm a bit picky):
Retainer2 copy.jpg
Retainer1 copy.jpg
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