The guides are looser than Edelbrock guides which I prefer. I found one very loose guide (.003 over) and the chambers weren’t finished on the same set. These were bare heads and probably would have hopefully been caught if they were assembled. This was out of about 15 sets. I don’t recommend running even the best heads out of the box as they should be taken apart, inspected, and cleaned. They have a very nice looking set of upgraded 1.5 rockers that I had in my cart several times.