30 vs. 45 degree valve seat air flow data

Many tracks run limited valve lift rules. Typically, these rules are in effect for the popular Chevy open chamber cylinder heads. The ‘487, ‘993 and ‘441 are the best heads to run in this class. We did a series of tests on open chamber ‘441 heads with 30 and 45 degree valve seats to see if there was an air flow advantage at low lifts when running 30 degree seats. Here is what data showed.

Test head: ‘441 open chamber head with “UnderCover Porting”.

Test Pressure: 28″ with radius flow guide.

Valve lift             30 degree seats                   45 degree seats

.100                             75                                         62

.150                           102                                         97

.200                           129                                       133

.250                           152                                       159

.300                          175                                       184

.350                           187                                       199

.400                           197                                       212

.450                           206                                      217

.500 .                         210                                       225

Conclusions: The 30 degree seats did produce more air flow below .150″ valve lift.

Above that lift point, the 45 degree seat angle was far superior.