12v & 24v Cummins Pushrods
Due to the overall lengths of the Stock 3/8 diameter pushrods being almost 11 inches in the 12V and 11.5 inches in the 24V Cummins, we feel the strength of the OEM pushrods are not adequate for anything other than a Stock vehicle. When the stress on the pushrod surpasses what is considered a reasonable window of operation, the OEM pushrod is not designed to support the additional load that the valve train system is experiencing.
To provide increased pushrod column strength and valve train stability, we offer both 3/8 and 7/16 diameter “3 Piece” pushrods. Our pushrods are manufactured with 4130/4135 seamless Chromoly tubing with a variety of heat treating conditions and wall thickness’ available, all coming standard with our billet steel tip ends. These tips have been CNC machined from 86L20 bar stock that are then core hardened and triple tempered, providing increased impact and wear resistance. This combination of materials and heat treatment procedures will extend the service life of the pushrod, while improving overall performance of your valve train. Our versatility in engineering and design allows us to manufacture a product that will enhance the specific combination of your engine.
When we sit down to engineer a pushrod, we always try to fit the largest diameter pushrod we can, within the space available. By increasing the diameter of the tubing from 3/8 to 7/16, we can spread the load over a larger surface area without causing the pushrods to bind with the port of the cylinder head. This larger diameter tubing will provide almost 2 times the loading capacity before the pushrod begins to deflect. Larger diameter is always a better choice when it comes to pushrods and is why we suggest 7/16 diameter in all Cummins engines.
With improved strength, performance and service life being our goals, we suggest upgrading pushrods to our Series 5 in all competition engines. If your engine is seeing an excessive amount of rpm, boost or nitrous, our Series 5 will provide an additional 105,000 p.s.i. tensile strength over our Series 3. The increase in rigidity will provide further accuracy of the valve timing and raise the point at which the valve train begins to surge. Our Series 5 pushrods are the strongest, most durable chromoly pushrods ever produced. This has been proven in our top fuel, blown alcohol, sprint car, cup, dirt short course, Baja, tractor pulling and offshore marine Champions, year after year.
Last but certainly not least, if you have made any changes to the engine requiring custom length pushrods, we sell pushrod length checking tools with proper ball and cup radius’ to replicate the OEM pushrod in both the 12V and 24V engine. Correct pushrod length will allow you to keep stock rocker geometry and therefore, allowing the scrubber cup of the rocker arm to correctly ride the contact area of the valve bridge in a 24v engine or the friction pad of the rocker arm to ride the valve tip in a 12V engine. If the adjusting screw is not at the stock position, it will change the ratio of the rocker arm, in turn affecting valve lift.
All in all, pushrods are a very important link in the valve train that are often overlooked at the expense of performance and service life.