how to set up infeed to grind.375 dia tube

[recker]

i need help setting up centerless machine to grind .375 tube 4 inch long .3 on one end and .367 on the other material is alum,

i try to grind after dressing wheel but get small grooves on the part (tiny lines about .0005 wide around the part) one or sometimes 2 in 4 inches, otherwise the finish is perfect. there is nothing on the wheel or the blade that i can see to cause this

when i feed a brass part the same size, it grinds perfect but the alum looks like garbage

coolant is hansterfers (very rich)
wheel is alum ox
machine is old cinci

please help, i have no more hair left as i have pulled it all out!
if you are in the phoenix az area i will reward you well if you can show me how to set up and run this machine
rogertilden@netzero.net