318 build

Dan the man said

How much bigger valve can you use before you have to worry about shrouding the valve by the chamber walls or the bore itself? Don't most street cars operate in the 1800-4500 rpm range for the most part? Would big valve's and ports really be necessary for a daily driver where the person is only looking for a boost in performance and not needing tons of power

Click to expand...

It’s mostly a target dependent issue. But yes a larger valve and port size is entirely OK. Valve shrouding is less of a cylinder issue and more of the heads chamber issue. Valve shrouding s an issue overly concerned about. While good to avoid, it’s not an issue to freak out about. Worry more about the head chamber itself.

As for myself, I have found the best engine power gains occur after headers, ignition and basic bolt on with the camshaft followed by complimentary head work. As long as the cam has a reason’s compression ratio backing it up and a good flowing head, the engine responds really well.

A low rpm engine doesn’t need a bigger valve in a mostly pedestrian setting. The OP did t give any duration numbers (& @ .050 and s best) to help this project along.

If this was my engine and destine for just regular driving around town with some added performance, I’d keep the 318 heads and call it good. The cams he listed above should be fine enough for low 14 second 1/4’s and duration dependent, at least 17 mpg.