Up until now, almost all of the American V-Twin motors have used a variation of the H-D lower end -- that is, knife and fork connecting rods running on a single crankpin that is mounted between two flywheels. The connecting rods use roller bearings at the crankpin. This system, which dates back to the '20s, works well in motors more than 120 hp that are operated at less than 6,500 rpm. All of the previous rules governing bearing life have changed thanks to MID-USA's new Powerhouse motor is based on modern two-piece connecting rods with plain-type bearings on a one-piece crankshaft.
The new Powerhouse motor is a joint project between MID-USA and long-time race engine builder Vern Ott. Vern originally developed this type of lower end in the mid-'80s for use in XR 750 dirt-track bikes. After a hiatus of several years, Vern had the idea to update his design for Big-Twin motors. The new motor is the product of Vern's design abilities and MID-USA's product development manager Larry Curik's skill at rounding up subcontractors who could make the parts to the high standards that Vern demanded. The result is a large-displacement motor, 114 ci, which to the untrained eye, looks similar to most Big-Twins. These motors can safely rev past 7,500 rpm. In base form, they generate 135 hp with 130 lb-ft of torque, but it can be hopped up to put out more than 150 horses without stressing the lower end.
The Powerhouse motor's parts come from some of the biggest names in the V-Twin performance business: Delkron, JIMS Machining, Falicon Crankshaft Components, Carrillo Industries, KB Performance, Comp Cams, Crane Cams, L.A. Sleeve, Velva-Touch, Hegedus Aluminum Industries, and Gardner-Wescott. Each motor is fully assembled, test-run through three heat cycles, and the valves and ignition come adjusted. The motors are also complete with a flange-type intake manifold and Crane ignition system, but less carburetor and alternator.
Vern gave us the cook's tour of how all these parts go together, and it was very impressive. So come with us now, and we will show you the first truly new V-Twin motor in a long time.
 |
The heart of the new Powerhouse motor is Vern Ott's crankshaft and connecting rods, which weighs 11 pounds less than a standard flywheel assembly. When we first saw it, the assembly looked so natural that we asked Vern why someone hadn't made it sooner. His answer was, "I did, about 18 years ago. But it took an awful lot of time and money to develop it for the Big-Twin motor." |
The rod bearings are the same size that is used in small-block Chevy V-8 motors. These bearings can carry a far higher load than the roller bearings used in the knife and fork rods that are found in regular V-Twin motors. |
The rod bearings are assembled into the connecting rods in the same way as most high-performance motors -- motorcycle and automotive. They fit into the rod's big end and use small tabs to lock into the rod. |
The H-beam connecting rods are made by Carrillo Industries, the same company that makes rods for Top-Fuel motors. The rods are not only super-strong, but lightweight. The rod's wristpin bosses are offset to allow the pistons to run on the same centerline. |
The motor is fitted with oil jets that spray the bottom of the pistons. This cools the piston skirts and adds lubricating oil to the cylinder walls. |
After the rods are bolted onto the crankshaft, the complete assembly is checked for runout. The average runout is less than 0.001 inches. |
The crankshaft assembly is fitted into the left crankcase, just like other Big-Twin motors. These crankcases are produced by Delkron. |
The motor uses a constant-pressure oil pump, also designed by Vern Ott. It puts out 43 to 44 psi at any rpm. |
Larry Curik holds the pistons while Vern aligns the timing marks on the camshaft and breather. |
The motor was designed for maximum reliability. It features iron lifter blocks; these are more compatible with steel lifters than aluminum. |
In order to support the increas-ed combustion pressure, the Powerhouse motor uses copper O-rings to seal the cylinder head. In addition, it features O-rings on the oil drain-back bushings. |
For compatibility, the Powerhouse motor has all its mounting surfaces and its intake and exhaust ports in the standard location. If we hadn't seen the insides, we would think that this was a regular V-Twin. |