I Bought A Set Of These Heads For My Chevy 350.i Havent Run Them Yet.i Had To Drill Out The Alignment Pin Holes,and The Valve Guide Bosses Look Like They Need Ground Waaay Down,they Are Huge Compared To Darts And A Few Others Ive Seen.they Cant Be Very Flow Friendly.but In All Fairness,most Everything About These Heads Looks Right.pretty Good Machine Work.valvetrain Pieces Look To Be High Quality ,i Would Still Like To Know Who The Pieces Are Made By.the Company I Bought Mine From Gives A 2 Year Warranty.they Did Take Care In Assembly,all My Spring Heights Were Perfect.no Way To Be Sure Except Fire It Up And See How They Run.