I've heard Chevy valves work in the Flatheads, what exactly needs to be done. I know to get 1.5" Exhaust valves, but I heard they are longer and need stems ground, possible spring shims, and do the ford keepers work with them or do you need to get new keepers? They're certainly cheaper.....

 

The keeper grove is a little higher on the stem, so you need to shim the springs a little. They are also a little longer from the keeper groove to the end of the stem, also. This problem might be overcome just by using adjustable lifters, but I'm not positive on that. The Chevy exhaust valves are a good step up in getting rid of that horrible lump under the valve head that the stock valves have. You can go one step further and use the 1.60 exhaust valves with undercut stems ( I don't think they are available in 1.50 dia. ). These are usually sold under the Pro flow/ Race flow names.