head comparison

The previously reported stock head flows are fairly correct in our experience, but probably more in the 200cfm range (412HP). An X, J, O, or U head with the 2.02 valve with a bowl hog and porting or hand bowl work and porting generally will max out around 240-245 cfm @ .450" lift (about 505HP potential) and stall above that. We have J heads with no welding or epoxy that flow 292cfm @ .600" and 298cfm @ .700" (some 600+HP potential). It is too expensive to bother porting a J head to those flows and a ported aluminum head is recommended for those power ranges.