W2 head porting observations help needed!
Test pressure was showing 4.8 @ .550 lift
That’s interesting. It’s higher than I would have expected by a fair amount for only having one vaucuum motor.
Imo, putting aside the actual numbers, if you’re able to pull over 3” at the higher lifts, I’d say the trends seen from the porting are going to be valid......... unless it’s a head that does something odd as the test pressure goes up(which some do, some don’t).
The old Mullen’s tests were done at only 3”.
It’ll be interesting to see how/if the numbers change with a higher hp vacuum source.
I’d def get some PTS plates before going too much further.
My understanding of how the shop vac type flow bench works is, there is no “flow control” to regulate the test pressure.
The flow bench is running at max pressure at all times.
As the valve in the head is opened, there is less restriction to flow and as a result, the test pressure drops.
The computer in “the box” is measuring the air flow through the flow element, and monitoring the test pressure, and calculates/corrects that flow, at that pressure(whatever it is), to what it would theoretically be at 28”(or you can select 10”).
When I had my SF-110, I would test the “big” heads(like a big BBC head or a B1) at 5” or 6” at high lifts.
Those benches have 4 motors, but only use 2 at a time(2 intake/2 exhaust).
So, for heads that were too big to be able to pull 10” of vacuum at the higher lifts, rather than use a lower test pressure for the whole test, I’d test at 10” until I got to a lift point where I couldn’t pull 10” any more, then I’d drop to 8”...... until I couldn’t pull that anymore, then drop to 7”, then to 6”, etc.
At that point I was basically doing manually what your “box” does automatically.
