I could be mistaking, but I thought I read somewhere that you can fit 318 valves into a Slant Six head. Is this true or just wishful thinking? If so, what other modifications need to be done, and do the gains justify the cost?

their are definitely better choices. with the small block valves being .3 inches longer than the stock slant valves, issues such as valve cover interference, unfavorable rocker geometry and spring problems arise.

Doc has said he likes the BB mopar exhaust valve for the intake.

I have seen many threads about the Ford 300 valves, and i have used 302 ford valves, but those require a different guide be installed. someone will come along with the link to the website that has the OS valves. SI valves is the name i think.

edit: here is the website

http://www.sivalves.com/

sb

Small block Mopar valves are not a good choice, there are better ways to go. I use BB Mopar exhaust valves for SL6 intakes and exhaust.
The 1.74 or 1.81 valve for the intake and the 1.60 size (361 - 383 BB) that has to be trimmed down to 1.5 to fit the SL6

These valves have 3/8 stems so guides are not needed. (that is, if your current guides are still good) These BB valves are appx. .100 longer so they use the taller installed heigth springs and work better with high lift cams.

For mild SL6 build-ups, the SI "drop-ins" or the Enginebuilder OS valves being sold on ebag are a great way to go.

If you need to install new guides, the Forrd or Chebby valves are a good alturnative but as noted, they use a smaller stem size.
DD