Someone explained on chevy that valve guide clearance can limit lift.
The measurement between the valve stem and valve guide which is the drilled machined hole in the cast iron cylinder head. .0015 - .0018 is the usual valve guide to valve stem clearance.
Picture your valve stem running down through the valve guide port. The valve guild has a two fold function. 1. to seal the oil from getting down into the valve. 2. To align the valve and keep it straight. If your valve guide is worn you will get a puff of blue smoke each time you start the engine. The valve clearance is the amount of distance the valve stem can move from side to side and that also also it to move in the lifter too which will take it over limit. If you install the incorrect valve guides, ie too small, they will not allow the valve stem to move as easily.
Valve guide clearance is distance between the valve stem and the valve stem guide. It is critical for proper engine operation.
You got a couple of things mixed up Valve guide to valve spring retainer clearance is what limits lift. Thats the space from the top of valve guide to the bottom of spring retainer. Or from a lift stand mount, how much the spring/retainter can move down before bottom of retainer hits top of the guide The valve guide clearance has nothing to do with lift. Its the clearance between the inside of guide and outside of valve stem. Pretty much the amount the valve can move left to right, fowards to backwards inside the guide
