Single or Dual Pattern Cam

273 said
Building a 340 - 360 is fairly straightforward. 273 -318 are not

4th way is to build like it's a 340, with a little more gear and stall, which it becomes a pretty straightforward build.

And to the OP if this is for a 318 why the 108 lsa??

Smaller engine respond *better* to a wider LSA.
(*street-street/strip, in certain parameters)
Building a 273/318-318 for this discussion, is straight forward. Building it like a 340 is fine for the most part. Certain caveats apply.

Dan the man said
The tighter lsa is good for low to midrange torque. From what I've read and heard, a 112* lsa is to wide. A few guy's on here have recommended a lsa of under 110. I just read last night that a 108-109 lsa is highly recommended for low to midrange torque

Normally speaking a tighter LSA will make more low end torque and peak earlier in HP.

12many said
Here’s a David Vizard method of selecting LSA: Engine C.I./8/Intake valve diameter = X

Example:

318/8 = 39.75

39.75/1.92 = 20.70

20.70 on the graph shows: 109 LSA

In his books he recommends rounding up if it falls somewhere in between The more common even numbered LSA’s

View attachment 1715832459

Change around with cubic inches and intake valve diameters can you can see the various LSA’s It comes up with. Obviously there’s more to it, but if you read some of his books and his theories on camshaft selection it all makes sense

Thank you!!!

toolmanmike said
Dual pattern cam. Best with a restrictive exhaust? Correct me if I'm wrong.

Correct. But also, the extra exhaust extends the power band. How much and how long are completely build dependent.