Like Pat said about tapering the leading edge, that is a good thing! Most of the guide manufacturing co. put a 1/4" of smaller od for the line up. The main thing is to get them started streight. I highly recomend using antiseize on the guides. they like to gauld.and if you do drive them in with a hammer, don't mushroom the top of the guide.If you do, you will have one more to practice on. While you have the exh guides out you might take out some of the guide boss that blocks the exh port. This will make them flow a lot better. the intake side is good just the way they are.I raced a bug back in the mid 70's with a set of modified dual ports (home made race heads) ran 11.50s @ 109 mph. Had a ball.Don't know what you are building, but a few mods can be done for free that make a big diff. Good Luck. Jeff