All 250 in line sixes were downgraded to the new Shell moulded cylinder bores, and the cylinder block and head castings from June 1968 were all downgraded to thiner "thin-wall" castings. There aren't any better ones, C9 or D8, any 1969 to 1980 US 250 block and head is going to be downgraded ultra thin-wall by new foundry Boss, Bill Gay.
The US 250 has many crank changes comparred to the later Oz 250....differing thrust bearing width, and main and rod bearing crush from the normally bomb proof Aussie Log, 2V, and cross flow 250 engines made from 1971-1991. Down here, taxi cab in line sixes were pulled and dropped into Oval track racers, and left stock except for sump mods, a big solid cam with adjustable earlier rocker gear, and three big 2bbl DCOE 45 Weber or Dell Orto DHLA 48 or SU 2 or HIF7 carbs on some sawn up and TIG welded concoction intake. And some home made tubing headers. Pistons, cranks, gearboxes, clutches, normally bullet proof.
The difference is...your Garden US V8 step up option 5.0 engines were always well furnished with parts around everywhere. The corporate edit from HFII effected the SBF too, the 302 is no were near as reliable as an endurance engine as a good A code 4bbl 225 hp 289, but it's always been a cake walk to any 5.0 from a 129 hp 1974 plodder to a 325 HP Fire brand with just Heads, Cam, Intake and exhaust.
Have a good rest. The late Al Turner and Bill Bourke were the North American guys down here who authorised many subtle endurance changes over the US 250 engine. It was 9 times out of 10 a manual gearbox engine in Australian cars, so the thrust bearing from a 3 or 4 speed clutch in bulldust conditions with bad oils and searing out back heat required different crank and con rod bearings, and that thrust bearing change was made for a reason. Repco, a consultant F1 racing company, supplied the bearings and did the development work for Ford's tall deck 200 and 250 engines, while doings Holden and Chrysler's work as well. So the somewhat incestous relationship between the Big Three in Oz, certainly didn't hurt reliability and endurance.
The oil pump and distributor hex drive pin differs too. So do the valve stem diameters and water pumps, and the quoted engine block weights of 407 pounds vary a little over the US 250s.
If I had to use the US 250 tomorrow, I'd rework the stock US crank to take the Aussie main bearings and rod bearings, and do the Mike1157 crank spigot mod, and use the US made, but Aussie spec Silvo-lite Hypereutectic pistons, and non HT989 solid lifters with the right solid lifter cam bearing change. That's a large cost, but as long as the oiling system has a restricted supply to the top end and good drain back and a good sump, with some good E6 1986 Ford Taurus 4 cylinder rods, you should have something bullet proof. People would line up for a solid base like that.
I feel many make excuses for endemic hi rpm, higher load reliability problems, putting down there own efforts they have made. Piston breakage, rod breakage, block cracking head cracking, crank walk, and very bad detonation are typical of this Ford engine. I know based on Ak testimony that the base six cylinder small six engines were was downgraded, and that's why Ak Miller decided to add turbos and automatic gearboxes to every US 250 he modified. I think something with a 4 grand rev limit that makes 185 HP with a draw through TO3B Garrett and a big fat 4bbl 600 CFM vac secondary carb with less than 9 pounds of boost eliminates big cams, big revs, and big oil downs.
How bout a totally stock engine with a 165 dollar BW blow through turbo and a 4000 rpm rev limit making 185 hp? Critical loads of all components should drop, and , as Duet Howlett said to Ak..."Stop all this messing around and try one of these whistles on there"
Here's what 9 pounds of boost does to a 3100 pound 4.1 liter Fuel Injected Falcon
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