The mechanical fuel pump pushrod is a pretty simple device. It joins a lobe on the camshaft (or an eccentric) to a lever on the fuel pump. As the engine (and consequently, the cam) rotates, the pushrod moves the fuel pump lever up and down, drawing fuel from the tank and relaying it to the carburetor(s).
Simple stuff. But as engine speed goes up, the fuel pump pushrod can float—just like a valve spring.
The fix here is to reduce the weight of the pushrod. Fair enough, but a potentially larger issue is when you add a steel cam, such as many roller examples, into the equation. Here, there’s a mismatch of materials. And that’s not good because it can cause premature wear on the rod or, worse yet, the cam.
Back when mechanical fuel pumps were the norm, engines pretty much all had cast cams. The steel pushrod would never wear, and the cam was happy too. But today’s steel cams cause all sorts of grief. A fuel pump pushrod can easily wear quickly or the end can mushroom. If it mushrooms, you might have a devil of time getting it out of the cylinder block. The fix here is to use a pushrod that is compatible with the camshaft.
Selecting a Fuel Pump Pushrod for a High Performance Engine
Prior to the move to electronic fuel injection, NASCAR cup car engines typically made use of mechanical fuel pumps. What plagues modified street or street/strip engines also plagued those NASCAR engines (keeping in mind some of those engines operated in the 8,000 to 10,000 RPM range and raced for 500 miles). Those cup car engines also made use of steel camshafts—some of which had case-hardened lobes.
While the mechanical pumps have been replaced today due to the conversion to EFI, mechanical fuel pump technology (along with mechanical fuel pump pushrod technology) has remained.
So what’s available? Summit Racing offers all sorts of solutions. Three examples from the Summit Racing catalog (for common Chevy engines) include a lightweight pushrod from Moroso, a steel pushrod with a bronze tip from Crane Cams, along with a composite pushrod from Howard’s Cams.
Moroso’s #65750 fuel pump pushrod is a lightweight design with hardened ends. The lightweight (approximately 64 grams on the writer’s postage scale) is likely half the weight of a stock Chevy pushrod. It’s designed to reduce pump float and, as a consequence, fuel starvation. While not advertised or sold for use with steel camshaft cores, some folks have had success with them.
The Crane Cams #11985-1 pushrod is heat treated and it incorporates a bronze tip (which is installed on the camshaft side). Crane Cams notes that it is specifically intended for use on 8620- and 9310-alloy steel camshafts along with hard-faced cams. It too is very light. On our scale, it came in at 62 grams.
The Howard’s Cams #94475 pushrod is manufactured from a proprietary polymer mix. Howard’s Cams notes that the bearing-grade polymer is reinforced with carbon. The polymer is very gentle on the cam lobe and it’s possible to use it on either cast or steel billet camshafts. Since it’s bearing grade, it is self-lubricating. These pushrods are extremely light—Howard’s advertises them as 0.9 ounce (25.5 grams), but on our postage scale it came in under 20 grams.
All three of the above pushrods measure 0.500-inch in diameter. The Crane Cams rod measured in at 5.758 inches long; the Howard’s Cams example measured 5.750 inches and the Moroso was marginally longer at 5.759-inches overall.
Installing a High Performance Mechanical Fuel Pump Pushrod
In terms of installation, they all go in the same way as a stock pushrod (keeping in mind the Crane Cams rod’s bronze tip must be installed with the tip facing the camshaft). Obviously, the bigger the pump capacity (and stronger the pump spring pressure), the bigger the risk of mushrooming a pushrod.
For a closer look at mechanical fuel pump pushrod options, check out the pics below: