Essentially Rhodes Lifters are like a standard item that has been "pre-worn" to a consistent degree across the complete set. At high rpm they behave identically to standard items. At low rpm, the leakage built into them means they react more slowly to what the cam is doing to them - they need "pumping up" on each occasion the cam lifts them. So the valve events start later than the start point you'd expect from the cam. They also finish later as the lifter follows the cam back down - effectively they have created a shorter than normal pushrod, which is of course why they are noisy at low rpm. Because of the slow initial response and conseqent effectively short pushrod, the valve won't open as far as the cam intended either.
So at slow speed, the engine behaves as if it has a cam with lower lift and valve opening times later, and valve closing times earlier than the cam it is actually fitted with. At low revs the low lift doesn't matter - it might actually help as it will raise the gas velocities into the combustion chamber, thus promoting better swirl and air fuel mixing.
On the inlet cycle, the inlet valve will open later and therefore closer to TDC. So the preceding exhaust stroke is able to complete more fully before the opening of the inlert valve provides an escape route into the inlet manifold. Note that the effect at high rpm is quite different - the exiting exhaust gas entrains the inlet air and fuel and helps start to suck it into the cylinder - that's why the inlet is normally set to open before TDC. The inlet valve closing earlier is also good, because this usually happens after BDC, so at low rpm the piston would have started it's compression stroke and be pushing some of the air fuel mixture back out into the inlet manifold. At high rpm this doesn't matter because the speed of the air and fuel rushing into the cylinder mean it has momentum and doesn't stop immediately the piston starts to rise.
On the exhaust stroke much the same sort of thing happens. The exhaust valve will be closing early at low rpm, so again there is less opportunity for the inlet and exhaust to be open at the same time. And again at high rpm, the momentum of the flow established out of the exhaust valve would have continued to suck the exhaust that way after the inlet valve opens as well.
Of course we are in compromise territory here, as an engine that is good at high rpm needs an inlet that opens a long way before TDC whilst an engine that's good at low rpm needs one that opens much closer to TDC, likewise for the exhaust valve timing. So "sports" cams that give good top end power pay for it by having poor low speed torque.
The net effect - and what is usually quoted in the write up for Rhodes Lifters - is that there is less valve overlap at low rpm. That's good for torque. So the main utility for these lifters is to allow a higher lift cam with greater valve overlap to be fitted without making the engine undriveable through lack of torque at low rpm.
So on to falcons question. The cam you've identified looks like a fairly torquey cam. So there's no point adding Rhodes lifters to it. Buy a much peakier "sports" cam to use with Rhodes lifters. But remember that you are going to notice their presence by a much noisier valve train at low rpm.
Hope that helps
Chris
