I believe that all of the King bearings are bimetal just they have a different method to their bearings. I found some more info
THE BENEFITS OF USING KING ENGINE BEARINGS
Tri-metal vs. Bi-metal Bearings
Traditional rod and main bearing construction is based upon a three layer configuration composed of a steel backing, a copper-lead layer and a very thin overlay of babbitt material only .0005" - .0008" thick.
King’s bearing uses just two layers, a high strength steel backing plus a bonded layer of "Alecular" bearing material .012" - .015" thick.
Alecular material is used exclusively by King. It is an alloy of aluminum, tin, copper and several other elements. Because it is an alloy, it maintains its properties throughout its entire depth, delivering consistent and reliable performance.
Benefit No.1 - Particle Embedability
More than half of engine bearing failures are caused by metallic particles which scratch crank journals and tear or weaken thin babbitt overlays such as in the tri-metal bearing.
Since King’s Alecular bearing layer is much thicker than the babbitt overlay (.015" vs. .0008"), it provides eighteen (18) times more embedability than a tri-metal bearing to catch and hold particles so they don’t scratch the crank journals. This is especially true for particles over .0004" in diameter which cause most of the damage.
Benefit No. 2 - Conformability
The much thicker layer of Alecular bearing material (.015" vs. .0008") allows the bearing to conform to problems such as metal to metal contact when there is mis-alignment present or the connecting rods stretch. Greater conformability means fewer bearing failures.
Benefit No. 3 - Temperature Resistance
The Alecular material’s melting/fatigue point is over 11000 F, almost three times that of the thin babbitt overlay in a tri-metal bearing (400OF). This means added protection against localized overheating due to mis-alignment, detonation, overloading, loss of coolant, etc.
Benefit No. 4 - High Load Capacity
Alecular bearings successfully withstand the stresses of blown, nitro-methane burning Top Fuel dragsters generating 5,000 hp at 8,000 rpm and in 700 hp circle track engines running for extended periods of time. The same metallurgical alloy is used in King’s street bearings that is used in King’s High Performance bearings, so the regular bearing user gets the advantage of the alloy developed and used in race engines.
Benefit No. 5 - Control of Wall Tolerance
Bearing -to- journal clearances on main and connecting rod bearings can be affected by several variables, all of which the engine builder must try to control. King has removed concerns about inconsistent shell to shell bearing wall thickness by the use of statistical control methods to keep wall thickness to very limited variation.
Other manufacturers produce bearings whose wall thickness at the crown can vary by up to + .00025". King bearings are produced using "Bull's Eye" specs which set a higher standard of controlling the wall thickness, permitting no more than + .00010" variation of the desired thickness.
The benefits of tight control of wall thickness tolerance are:
Improved consistency of bearing to journal clearance. No more trying different bearings within a set to get the "right" fit.
Superior eccentricity and crush relief values for a better oil "wedge" and less journal wear.
Less taper across the bearing face, meaning superior wall stability, a more parallel wall and better oil film development.
Crankshaft grinder does not need to grind cranks "fat" or "thin" to compensate for bearing variations.
Benefit No. 6 - Crankshaft Endplay
All bearing companies solve crankshaft journal wear by supplying oversized bearings. However, King went two steps further with the development of Max Flange and Pro Flange. Max Flange reduces endplay by supplying the flange on the high side of the tolerance to compensate for crankshaft thrust surface wear; this process is used on all King bearings. Pro Flange are bearing sets supplied with oversized flanges allowing the thrust surface to be ground to .010", .020", or .030" undersize.
