#920 vs. #675 Heads "Compression vs. Cylinder Flow"
Cudavert,
Thanks for the compliment.
Numbers
The #920 Cylinder Head gives you about .35 more compression than the #675 Cylinder Head,
when calculating 57.3 CC's - to - 60.6 CC's.
Probably about 5 more Horsepower. Track numbers result was -.09 Elapsed Time and +.63 MPH
better performance with the #920 Cylinder Heads.
Though, I agree that the #675 has a little better cylinder-flow which closes the gap difference a bit.
Since the 'stock' 273 Commando Camshaft {.425" Lift ~ 248* Duration ~ 26* Overlap} was used,
there is no real issue with valve-shrouding in the #920 small combustion chamber.