Ferrea, REV, SI, Manley, are a some of the manufacturers that can help you with any valve size, stem size, stem length you will need.  As a retired automotive instructor, I personally would not recommend what you are suggesting for the valves.  Saving a few dollars on a questionable project might cost you hundreds of dollars later when the keepers pull through, and a valve drops.  Just because something can be done does not mean it should be done.  Joe-JDC

JDC

I figure the race guys should know this stuff because they do need custom stuff from time to time. There arent too many options when you get into offbeat stuff. I've actually got a few different projects that need custom valves, ones a 331 hemi running ported industrial heads, anouther project needing valves that i have in the planning stages is a flathead 6 running harley cylinders on a custom bottom end for a possible drylakes project, lastly i need these 235 valves for a 283, for a vintage hot build. Also i'm in the planning stages for a 312 build for my daily and i may be looking to bigger valves for that too

Don't see anything "racy" about cutting scruby valves shorter in this forum.  Sorry, but that is not something for this section.  Valves can be bought for just about anything imaginable if you search the internet.  Not meant to be snide, but this is not the place for that type of question.   Joe-JDC

JDC

I've got an OT project that requires custom valves. I'm looking at shortening some 1.87 GM 235 6 cyl valves for it. Do i have to worry about the valve retainer groove being soft when i recut them or are valves the same hardness all the way thru?