cylinder head id

krazykuda said
They had to increase the flow of the bb head after 67 because with the launch of the 340 in 68, if they didn't improve the head flow, the 340 would have been better than the 383...

That's why the output on the 383 jumped 5-10 horsepower after 68...

Some people like to use the pre 67 heads with the closed chamber to increase their compression.
Click to expand...

Partially correct,

The reason Mopar went to the 'Open Chamber' Cylinder Head in 1968 for the
Big Block > was to reduce emission's at low RPM's to meet EPA Guidelines.

Also, the 1968 383 had an improved design in the Cast iron Intake Manifold, and better Carburetor with the Carter AVS {630 CFM}.