5/16" valve stems on intake lash changing?

[Joe-71]

Lobe lifts are not identical( 7* more exhaust). Pushrods are identical. Trend tool steel lifters(solid). All bronze guides, Manley premium custom valves one set of heads, and Ferrea custom valves in other set of heads. Only the intake valves lash closes up when hot, and returns to normal when the engine cools down. Fresh plugs, MSD wires, MSD distributor, MSD 6AL, 110 VP. Tried two distributors, three 6AL, indexed plugs, etc.. I have never experienced this in my 57 years of building engines. Third set of heads with 11/32" valve stems did not increase the lash on intakes. Joe-71

[frnkeore]

Is the shape of the under side and top, the same on both size valves?

A little test that you might do, using a surface plate is set a indicator on the cold valves, then heat both size valves, to the same temp, using a hand held pyrometer. Place them back on a surface plate and see if the length grows at the same rate. Then deferentially heat them and measure that, too.

[raynorshine]

ran a Lunati solid roller...5/16" valves...steel 292 heads...for years and years...hundreds of passes...maybe thousands..never a problem

[MadBill]

I don't know what alloys either of these mfgrs. use for their valves, but per below example of a few of the many SS alloys, there can be a big difference in expansion rates:

Product Linear Temperature Expansion Coefficient - α - (10-6 m/(m K))

Steel Stainless Austenitic (304) 17.3
Steel Stainless Austenitic (310) 14.4
Steel Stainless Austenitic (316) 16.0
Steel Stainless Ferritic ...(410). .9.9

191 more rows
Coefficients of Linear Thermal Expansion - Engineering ToolBox