318 Build

Davidrad said
I'm going to find a 360 and install a set of domed pistons. Seems like the easiest thing to do. Raising the CR isn't really an issue, I was just hoping for bolt-ons. My normal machine shop only charges me about $150 bucks to mill down the pair of heads if I go that route. It's the fitment issues, springs, rods, rockers that scare me now. Dealing with smog motors and having a piston so far down in the hole is bound to create problems. I've learned a ton by this thread, and been scared a bit by this thread. DCR isn't something you hear about but it makes more sense as a measurement that SCR. You guys are the best and thanks for putting up with me.

Well, I hope 'scared' is not what you takeout of this. Things just are what they are.... low compression just is hard to make up for with performance engines.
The 360 idea is a surefire way to go for the 'tire-spinning on demand' that you mentioned. Longer stoke, more cubes, and if you start fresh, you can put things where you want.
Since you mentioned the domed pistons, then it is probably time to touch upon the opposite corner of the compression ratio map, where you get it too high in CR. That leads to detonation problems. Every engine ever built since the 50's or earlier would have had 10:1 static CR or more, if this was not an issue. The limit is best expressed in DCR again, where if you get too far past the low 8's then you move closer and closer to possible detonation issues. Some have made things work on the high 8's but you had better be on your tuning game all the time and get consistent gas. Or run race fuel.

So you can see we are always playing the game of upping CR but not so much to stray into detonation-land. It just 'comes with the territory' of using gasoline fueled, spark ignited internal combustion engine technology.

As a side note, some of the newest gasoline engine designs in the world are now using gasoline direct injection (direct into the cylinders, like a diesel) but with diesel-type compression combustion. That gets the SCR's and DCR's up several points, and the torque and combustion efficiencies take a big step up. But you just cannot go there with spark-initiated combustion and gasoline fuel.