i cc'd the intake runners of a 3900 head

[Guest]

Ben at WOT? Anyone?

curious if anyone has cc'd the intake runners and or exhaust runners of the 3400, lx9, or 3900 heads and what the numbers are. I want to do it myself but if someone else already has the numbers it will save me time. thanks

[Guest]

So i did my mildly ported lz9 heads. I gasket matched the intake runners and cleaned up the bowls. I raised the roof in the exhaust port by a little bit, and cleaned up the bowl.

the runner volume is as follows.

intake 131cc
exhaust 75cc

unmodified will be a bit lower but it will give you an idea of where its at.

it was mentioned these were modeled after the ls1 heads. It seems so on the exhaust side, and the rocker arm ratio more than anything I think. The intake port I thought was gonna be closer to 160-170cc. I think ls1 heads are 190-200cc or so on the intake side and 70cc on the exh.

I am curious how these are able to provide the airflow for a bore the same as a ls1, albeit a bit less stroke, and still provide good top end power. Ideas? Canted valves can't be the sole reason?

[SappySE107]

cc numbers are listed with the flowsheets on this site. You cannot compare with other heads of a different design because we are missing the portion that is in the lower intake, that would be included with V8 heads. You shouldn't have modified the 3900 heads. Maybe larger valves will help, but porting, especially gasket matching, shows decreased flow values on the flowbench.

[Guest]

I plan to flow test when I get them assembled. I don't have a before number though so ill have to go with what others have flowed on a stock head and compare yo mine

[SappySE107]

You want test springs, not actual valve springs on it for a flowbench. I posted some 3900 numbers in the past, but I will probably end up testing the larger intake valves this year as well. I don't know where any of the stock valves are at right now though. Link shows where the WOT-Tech/60DegreeV6 bench stands compared to other benches that have flowed the "pass around plates".