A few points of reality. A reality is that in Australia, the factory OHC is the Ford engine to have if your going to slam the hammer down without any modifications
Pros:
1. Even an early OHC has a rev range 500 rpm greater than any X-flow.
2. Later OHC's are able to rev 1000 rpm more, while still out-torqing an X-flow. XR6 and VCT and the later EL rocker gear is very efficient.
3. Size for size, and matching a carb with a throttle body OHC, and an X-flow EFI with an OHC multipoint EFI, the OHC has only 3% more torque but up to 15% more power than the X-flow engine.
4. The best multipoint OHC has more than 25% torque than the worst XC engine.
5. An OHC MPI or XR6 out of an XG ute will have a 50% to 62% boost in power over what a stock carby X-flow will produce, and 12% to 20% more torque.
6. The block is trim, tough as teak, and has the same phyical crank dimensions as the earlier X-flow, but each year, the OHC got better and better. The longer AU/BA rods were a huge leap forward in strength.
7. The earlier 1988 to 1997 rods in OHC's were 250 style rods in height and everything bar the bolts was similar. Beam section (the amount of steel if you cut it in half) was still modest, as it is in most American designed engines. The Geelong factory always made their rods out of forged steel, and they had good quality.
8. Ford did designed the 3.9 OHC with an AIT turbo system in mind, but AIT went bust before the EA26 cmae out. The rods are still able to take a huge level of boost, right up to 260 kilowates or 350 hp, the equal of a Phase 3.
9. Sooo, a the best OHC is a killer engine which is light years ahead of any stock X-flow. No argument. People like Aussie 7 Mains an the other Pro Sohc-ers are totally right about how exceptional this engine is. It's like comparing an X-flow with a 265 Hemi, the Ohc IS THAT much better.
Cons.
1. Rocker Gear. It's not bad, its brilliant, but its the most mis-undestood set-up around. There isn't an engine which has been more messed up than the aftermarket OHC!
All Ford OHC's all over the world ran a similar variable ratio lifter. It was supposed to be a constant ratio, but tollerances cause variations in ratio from the ideal. Yes, OHC Fords varied in valve inclination since the first factory OHC in 1969 , but basically, the 20 odd years of solid lifter Cortina 2.0, the 15 years of the hydraulic lifter Escort 'Erika' 1.6 CVH, and the 15 years of the E, and A series OHC's were just big versions of the European OHC's. The Falcon engine has the Compound Vertex Hemi head, it's a direct copy of the Front drive Erika Escorts.
A study of any Ford SOHC rocker gear is that they are designed for very high lift rates with very little expense.There is no margin for alignement stuff ups, or even 25 thou of valve height missmatch will screw up the total lift of the valve. Tiny things screw it up.
Anything you do to the valve spings, rockers and valves which is not to the stock EA, EB, ED, XR6 or late EF and EL upgrades will hurt the existing engine torque and peak power figures. The variable rocker gear lift to valve length ratio was described in detail by David Vizard in 1988, and it is very complicated. He talked about 1.63:1 ratios or more in the Cortina, while the Falcon is 1.8 or 2.0:1 depending on model. But it varies if your rockers are not EXACTLY aligned or the right length or depth. A base cricle diameter change in a remachined cam messes it up.
The likes of Jim Mock thrive on OHC's because everyone else is too lazy to do the hardest job with Fords OHC rocker gear, and that is...understand how it works!. Put different valves, the wrong springs, the wrong lifters, the wrong cam, the wrong rockers on, you will wonder why it performs so poorly.
2. The Electronics. I am not a total Ludite, I know the value of everything Ford engineers did with electronics. They are champoins, and possibly saved millions by ensuring no-one can fiddle with perfection!
In 10 years, the Falcon six exceded the power of a 4-BBL XC 351, and the torque of an XD 4-BBL 302, with just a good head and great engine management system. Using 30 % less fuel, and in cars which were heavier than the XD's and XE's. The EEC was at the time the most advanced engine control system around, but it was like the flat head Ford, ....one of the most stubborn to access for performance. Since the Aussie set-ups varied a lot fom the US versions, it is only supported by a few supliers. There was a huge level of customised binary chip characteristics. The variance between manual and auto, XR6, Ghia, XG and XH versions, to the base versions was significant, and then all the EF and EF11 and EL and the EA 1 and EA II, EB, EBII, and ED had massive changes. Some versions had no distributors, which is a bit of a laugh. Ford don't support all the parts any more, and when something breaks, it doesn't always invoke a limp-home mode. When you go to replace it, the piece must be the same.
That is the one thing I really dislike about OHC Fords. They make you learn all the model changes, and force you to work through the break-out codes. You have to do everything to the factory process, and if the fault is an ignition coil or stepper motor, or some basic system leak, you have to sort through the whole thing, like a swaring saint.
3. The BTR packages are linked together by unique bellhousings which make it a major undertaking to put the better,cheaper US V6, 300 I6 and V8 gearboxes in them. You can't easily divorce the BTR LE and T5 gearboxes and wack in simpler AOD or A4 Explorer 4-speeds, 300 i6 C6, or import Mustang T5 and T56 6 speeds. Even Ford Australia had a heck of a job making good T5 gearboxes for there rally Group N and Group E Falcon XR6 SS's. For Ford, they had to make a V8 T5 with a ohc main shaft and told the racers not to break them. All becasue Ford Australia decided not to use the six bolt V8 bellhousing. In the old days, a six cylinder Toploader or single rail were the same, and a six cylinder C9 could be mated to a V8 C4 and vicky versa. These days, everyhting is optimized to suit. The six has a huge amount of metal saved by running the smaller six cylinder bellhousing mounts, and Ford designed all sixes for Turbos, and put the starter where the back of the OHV cam was, so there is no interchanging an old C9 or C4 without a a modifed cistom bellhousing.
You would think 9 pluses and only 3 minuses makes the OHC a winner. When you add up the cost of the 3 minuses, the OHC is a 4 grand liability, even if you picked one up for 250 bucks. If all the gear is there, sweet. If its not, then unless its an XR6 or later Ghia engine with a good trans and all the bits, it is a 4 grand liabilty.
Playing devils advocate further.
Because the right head bits, electronics and gearboxes are so impossible to modifiy without a drug dealers credit line, I refuse to work with the OHC. I have to know all the bits are there, and easily understood, AND THEY ARE NOT.
Anyone can make a good old X-flow do 260 kilowatts with 4 grands worth of quality engine rebuild, and 4 grands worth of turbo. Add a good C9 or Supra 5 or 6 speed. Any OHC can be had for less, but the gearbox and elctronics and head eliminates cheap up grades.
Addilitinally, only a tiny amount of less than 60 000 sales of Ford OHC sixes were made each year by Ford Australia. There is no way the OHC will ever have the parts back-up they have with the US Windsor 5.0. Even if people started putting DOHC heads on the tomorrow, they'd still have to wok over the electronics and gearboxes.
The Falcon OHC will never have the impact on Americans the way the 2V or X-flow has becasue it has advanced along its evolutionary path too far for the parts supply. The OHC is as far removed from the early ohv and X-flow Falcon sixes as a Super Bike is from a peny farthing!
It's one of the best engines around. It's just that if you want to do anything to it on a budget, it screams Noooo!