notched cylinders 67 400?

Why are the cylinders notched?I have #142 small valve heads,094 small valve heads.What i'm looking to do is use the 67 400 nice nasty cam and by jim hands thery i can run 10.1 and use a more radical cam.Witch heads to use?It will be biult and stored away for use when my current 400 bite's the dust.so i have time.can i use a .500+ lift cam with the higher 10.1 cp?what will work best with what i have.the 094 heads are on a 66 326.thanks  

The bigger cam will only bleed off compression at idle and low rpm's so unless you will be idling around with it all the time then 10:1CR is too much for a iron head Pontiac engine regardless of what any one tells you.
Stock Pontiac D-port heads flow there peak at around .450-470 lift any more than that is just useless unless you have the heads ported and they do a good job.  
professional hi-performance engine builder.
Horsepower sells engines and torque wins races

+1
So more is not better

 
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