318 Poly Flow Test
Here's the results of the 318LA vs 318 poly flow tests. Both of these heads were old, came off of 100,000 mile engines and look to be bone stock. This test proves nothing, but it is a fun comparison.
Notice how the superior breathing capability of the poly shows up at higher lifts. This is because of less shrouding (a better utilization of the entire valve perimeter), less loss of short turn flow, a less obstructed port and a slightly larger valve.
It would be interesting to put the same valve job on both heads and retest. It's hard to compare the two heads now because the quality of the valve jobs is unknown.
Here's the results of the 318LA vs 318 poly flow tests. Both of these heads were old, came off of 100,000 mile engines and look to be bone stock. This test proves nothing, but it is a fun comparison.
Notice how the superior breathing capability of the poly shows up at higher lifts. This is because of less shrouding (a better utilization of the entire valve perimeter), less loss of short turn flow, a less obstructed port and a slightly larger valve.
It would be interesting to put the same valve job on both heads and retest. It's hard to compare the two heads now because the quality of the valve jobs is unknown.