Flow testing was performed on one of the two state-of-the-art SuperFlow 1020 benches available at Watson Racing and Engineering. Among other things the shop also has a SuperFlow engine dyno, a Spintron (to anaylze valve train movements) and a clutch dyno.	A 4.060" bore fixture was used to simulate a typical Ford engine block. Mike Blackstone gets ready to mount the head by placing a Fel-Pro gasket on for sealing.
With the combustion chamber lined up over the cylinder the head is clamped into place.	Industry practice is to use a clay-lip or Plexiglas fixture to provide a radiused inlet to the intake port. Flow would be way to turbulent without it, but Mike recommends that flow should be measured with the intake manifold to be used bolted to the head.
Mike bolts up a ported Victor Jr. intake manifold to show us how this really gives a more realistic picture regarding intake runner flow. The process Watson Racing and Engineering uses is to first flow the head with a clay lip. Then the customers manifold is bolted on to measure the loss in flow. Finally the intake is modified and ported to address any restrictions.	Flow testing the exhaust side follows a similar principle as the intake. A pipe is bolted to the port to simulate a header. For our RHS head testing we used a 1 5/8" pipe as this would be the diameter of a typical street header. Without a pipe the flow numbers are significantly worse, and it is also possible to see how a pipe with too large of a diameter also hinders flow due to excessive turbulence. Watch a Video of the flow test. (QuickTime)

Results
When a guy like Mike Blackstone says he is impressed with the results of an out-of-the-box cylinder head that means something. The RHS heads performed beyond expectations. The 180cc head demonstrates great flow in the low and mid-lift range, where the valve spends most of its time, while hitting 270 cfm intake flow at .535" lift. Mike notes that the flow does drop off sharply after .535" which will limit camshaft selection. This flow can be improved upon with some porting and better valves.

RHS Pro-Action 180cc Test Conditions Flow Bench: SF-1020 28" H20 Intake: 2.080" Valve. Clay Lip. Exhaust: 1.600" Valve. 1 5/8" Pipe.

The RHS 215cc head is the real performer. Normally with that large of an intake runner you expect to sacrifice low-lift flow. Mike, like many experienced cylinder head specialists, is very cautious that while flow-numbers are thrown around like dyno numbers, the importance must be placed on fuel control. A head that is too big for an engine and that has poor low and mid-lift flow will inevitably make less power. The 215cc head surprised us both with better low and mid-lift flow than the smaller 180cc runner. The larger runner really takes over at .500" lift where it continues to flow well up to .700" and break the 300cfm mark.

RHS Pro-Action 215cc Test Conditions Flow Bench: SF-1020 28" H20 Intake: 2.080" Valve. Clay Lip. Exhaust: 1.600" Valve. 1 5/8" Pipe.

Tips from the Pro
We showed you earlier that all three of the RHS Ford heads share the same exhaust runner and valve size. Thus is was a surprise for us to see the 215cc head display poorer exhaust flow than the 180cc head. For both tests we used the same 1-5/8" pipe to simulate a street header. Mike tells us that this is not uncommon and likely manufacturing variance. In fact had we tested more than one port on each head it is likely we'd also see similar variance. This is why Mike believes it does pay to spend a little time going through each port on each head before you bolt it on, including checking each and every spring pressure and installed height and making adjustments for cam to be used.

Mike Blackstone give us some tips on how to improve on the impressive out-of-the-box performance of the RHS heads.	Despite the great flow from the as-cast RHS heads, there is still room for easy gains. Here we see a casting ridge and slight lip between the exhaust seat and bowl. Smooth them out for easy gains.
Mikes take-home message for making power is the importance of proper intake manifold flow in conjunction with the cylinder head. This Vic.Jr. is heavily ported to a Brodix head. We bolted it to the RHS 180cc head just to get an idea of its impact. The head lost 12cfm in flow at max lift due to a slight mismatch between the manifold and head. You can't rely on head flow alone to make power.	Don't try this at home. Mike shows us the stuff Watson Racing & Engineering comes up with from their Pro-Stock and Super-Stock race engine programs. That intake port is from a SBC Chevy head, note the welded in and scuplted flow fin.

Mike points out that the 180cc head displays a very high exhaust to intake flow ratio (between 75-80%). His advisce is that camshaft selection for this cylinder head, on a naturally aspirated motor, should entail a single duration cam (e.g. 230/230), or even a reverse duration (230 intake / 228 exhaust.) Naturally total valve lift with any cam should not exceed the lift at which maximum flow is achieved. We'll take up his recommendations in an upcoming issue when we bolt these heads on a motor.