Well, lots of people have used old L67s in their cars, like mine, but it is up to you. Hopefully it isn't anything major though. When I got my engine all back together my lifters were loud as hell, until I pulled them and cleaned them. It could also be a chattery rocker, but that typically goes away with rpm... Your best bet is to get somthing to listen with (long screwdriver works great) and poke around. Try to eliminate as much as you can when you get the chance, and let is know. Good luck