Technical Information

We are the first and one of the ONLY maufacturers of a two-piece forged rod in America (made in America). The reason for using a two-piece forging is to keep the big end of the rod round. This is achieved when the beam portion of the rod's grain runs vertical and the cap portion of the rod's grain runs horizontal. Due to the two different grain directions, the big end stays round. The rods are either made of 4340 CHROMEMLOLY or TITANIUM.

HONDA ROD INSTALLATION

IMPORTANT

When installing Honda rods in your engine, you MUST install the rod bearing tangs towards the dip stick side in order to achieve proper fit for engine operation.

TWO-PIECE vs. ONE-PIECE FORGING

Most all of our competitors manufacture their connecting rods from a one-piece forging. It is cheaper and faster to manufacture rods using this method, but what is the real benefit? We do not think there is any. When a one-piece rod is first forged, it rough forges the big end bore at the same time. This stretches the rod's grain structure outward from side to side and around the big end bore. It's almost like pushing a pencil though a piece of elastic. When you look at a cross-section of a one-piece forging, it looks like a plank of wood with a knot in it. You can see the grain running from top to bottom and when it gets to the knot, it flows around the knot. All metal has grain and all metal has memory. The majority of the rods that customers have sent to us over the years all seem to have the same problem. Either the big end of the rod has turned blue from excessive heat or they have broken 1 to 1 1/2 inches below the wrist pin. What we believe has happened is that the one-piece forged rod's big end bore tries to go back to its original condition and it wants to close up. It becomes egg shaped. It gets smaller from side to side than from top to bottom. We believe this is what turns the rod blue. With this out of round condition, the bearing will eventually fail. The breaking problems we believe are due to the H-beam style. The webs are too thin and they fatigue. We have not seen this problem with an I-beam style rod.

We at Cunningham Rods feel that the correct way to manufacture a connecting rod is by using a two-piece forging and simulate the shape of a slice of pizza (triangle shaped) for the maximum strength. We all know that's impossible due to clearance problems. So the way we achieve this goal is to manufacture all of our rods in the I-beam configuration so that the main mass of the rod is out as far as possible. Making it similar to a pizza slice or triangulated for maximum strength. We do not feel that an H-beam style rod can accomplish this. You cannot get the main heavy mass of the rod out as far as you can with an I-beam style rod.

We manufacture rods for anything. Airplanes, boats, cars, motorcycles, trucks, tractors, you name it, we make it. We are known as THE UNCOMMON ROD SPECIALIST, making rods for over 30 years.

All of our rods receive the highest quality rod bolts. We have our rod bolts manufactured per aircraft specifications from AISI H11 tool steel rated at 296,000 psi. The threads on the bolts are roll formed, not cut threads.

TORQUING ROD BOLTS

With engines that have two connecting rods side-by-side, it is necessary to place a feel gauge between the two rods to take up any space before torquing. This will eliminate any flat spots that can occur when torquing bolts.