William, as you know the only way to have a great engine is to build one. It's certainly like that with Ford rods!
Economic rods worth looking at are
the imported OHC 4 Pinto (70-73) 2.0 liter rod 4.96" centres,
New, custom US Scat 5.0 Windsor rod with 5.09" centres.
I4 Holden 1.9 rod (5.25"centres, and needs custom ground crank, and shallow pistons to fit a 200)
On 186 to 202 cube engines, Aussies tend to use very light 0.866" pins in 5.25" size, and tend to go down to a 1.9" crank pin and have used Holden Starfire, Phase 3, XU1, or 3.3 XT5 rods. These have Ford DOHC Cammer size gudgeon pins and are mated to the best ACL or Duralite pistons. Rod brakage in this Holden rod is very unlikely, as its been made since 1973 to 1985 with its use in 7000 to 8000 rpm race applications with total sucess. It was designed to cpe with 500 mile rcing at Mount Panarama, and was used in the fird Torana GTR XU1 production racers.
Shame is, on any thing over 200 cube engines, your choices go up dramatically. These days, a set of US Scat, Dart, Lunati or other name brand forged items are the best bet if you are making between 1 and 50 engines a year.
1500 HP turbo I6's about the 250 cube or 4.0 liter size just use them in US long rod Chevy Small Block sizes, and they tend to use 6" rods with 2.1" big ends and 0.927" pins with custom Subaru or Chev 305 piston sizes.
Still talking 250 engines, If you want to, some of the emerging Ford Falcon I6 rods as used in the Aussie F6 Turbo are the unbeatable economy rod, able to hack 600 hp without any thing more than basic prepartion. Ford's Aussie I6's have had upgraded US 250 style 5.88" rods since 1971,
in 1988, the same sized rod in the OHC 3.9's went to a metric bolt,
in 1998, a longer 6.06" rods,
in 2003, the XR6 Turbo/LPG rod with extra under pistion oil hole reworking,
in 2004, there was the optional F6 rod used in the Tornado and Typhoon Turbo Falcons.
The stock forged 250 rods can hack 360 to 400 hp turbo intilations with ease. The OHC3.9/ 4.0 rods are better for 450 hp or so. The F6 rods are bombe proof. 600 hp has been delivered with stock F6 rods.
Getting back on topic.
There used to be no doubt a classic
mass produced Forged rod was an unbeatable economic position for a high performance engine. Downside is that Forged rods traditionally have very high Rockwell (hardness) readings, which makes machining them very hard unless you spend big on the maching tools.
Cast rods are way cheaper to make, and the production engineers then focus on bolt and grain quality to make up for deficiencies in ultimate tensile strength.
My understanding is that Powdered metal rods are forged rods with a very low Rockwell hardness. They are made for a purpose, and that is increased strength without increased production cost. They are finite element rods, and specific to an application. Unlike earlier forged rods, you have a minimum of metal, and they are designed for mass production orders right off a CAD machine. Example here on Fords Navistar Diesel rods.
http://findarticles.com/p/articles/mi_m3012/is_5_183/ai_101939306
The process was first employed in as so-called
Crack-off rods like used in the Ford Romeo 4.6 SOHC from 1991 onwards. Both caps and rods are forged together. Then, a stamping die 'cracks off' the small tonge of material linking both parts, and the two componets are then machined together with the same characteristic grain size, hardness and composition. Fords rationale was that any rod cap and rod beam metals fret against on another under with load, and if they have the same characteristic material compositions, they last a lot longer under loads.There is no abrassion when similar metals are bound together with good fasteners.
These days, Ford spends more money on bolts and bolt torque specificatiosn and metal cycrogenics and understanding metalugy than trying to find higher quality metals. Economically, all new rods are finite element designs, which work okay for there apllication, but have no excess lazy metal like in the old forged rods. Ford rods are throw-away items, a one time prospect. Old forged rods were not.
