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GM Head Casting Numbers

The lower the cc's the higher the compression.

Casting # Years
made
Valve
Size
HP Chamber Size / Notes
3782461 61-70 1.94/1.50
& 2.02/1.6
250-375 64 CC Chambers
No bolt holes
These are the double humps.
3890462 62-68 1.94/1.50
& 2.02/1.6
250-350 64 CC Chambers
No bolt holes
These are also double humps.
3927185 69 1.72/1.50 200-210 70cc Chambers
3927185 69 1.72/1.50 200-210 70cc Chambers
3917293 68 1.72/1.50 210 76cc Chambers
3917291 62-69 1.94/1.50
& 2.02/1.6
275-350 64 CC Chambers
No bolt holes
These are the 'Turbo' heads.
3927186 68-72 1.94/1.50
& 2.02/1.6
290-370 64 CC Chambers
has bolt holes
These are the 'powerpack' heads.
3932441 67-79 1.94/1.50 250 & 255 76 CC Chambers
Intake flow 152 CFM
Exhaust flow 93.2 CFM
3947040 68-70 1.94/1.50
& 2.02/1.6
290-370 64 CC Chambers
3947041 68-70 1.94/1.50
& 2.02/1.6
290-370 64 CC Chambers
3973414 64-70 2.02/1.6 360 & 370 64 CC Chambers
Z-28 & Corvette LT-1.
3973487 68-79 1.94/1.50
& 2.02/1.6
165-330 76 CC Chambers
X casting has 10 more intake
cc volume.
3998993 68-79 1.72/1.50
& 1.94/1.50
115-175 76 CC Chambers
Intake flow 150.8 CFM
Exhaust flow 91.1 CFM
333882 70-80 1.94/1.50 150-180 76CC Chambers
Intake flow 137.2 CFM
Exhaust flow 95.4 CFM
462624 76-87 1.94/1.50
& 2.02/1.60
Not listed 76 CC Chambers
These are crack prone!


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