I can't seem to find if there have been any problems with the stock valve guides in the M8 heads, although I see they are often changed out for bronze ones. Also, have the valve seat issues in these heads been resolved? - Rob
I haven't seen any problems with the stock guides.
As far as the seats go I think they got it sorted out but don't quote me on that. The early heads were a little thin in places. The later heads look better. I've also seen different seat material used in the exhaust seat which surprised me because they've been using the same seat material since the late Evo days. All the ones i get now have that type seat & I don't see any signs of movement.
It reminds me of when the Evo first came out. Those heads were thinned out in the beginning. When problems started showing up they added a little more material in the right places. Problem solved.
It doesn't take much to go from bad to good or good to bad. There's some things you just can't save money on.
Thank you for your input wfolarry. - Rob