Page 4 - Along the Way December 2020
P. 4
FORMANCE PUSHROD TECHNOLOGY
BY MIKE MAVRIGIAN
Car may feature solid tool-steel with no Correct pushrod length is key in obtaining a center
oil passage to the ball stud through the contact sweep of a roller lifter to the valve.
pushrod body, a 3/8” ball at the lifter
end and a 3/8” cup at the rocker end, in
diameters of 716” or ½”, hardened to
54 to 56 Rockwell C.
Pushrod diameters and wall
thickness obviously play a major role
in stiffness and resistance to deflection.
However, body diameter is much more
crucial as compared to wall thickness.
Regardless of the application, the rule
of thumb is to run as large a diameter
as possible, given the clearance confines.
While 5/16” diameter may be suitable
for a mild street application, as factors
such as compression, RPM and spring
pressures are increased, the need
increases for greater pushrod diameter.
Diameters ranges include 5/16”, 3/8”,
7/16”, ½”, 9/16” and 5/8” and in some
extreme cases, even ¾”.
As noted earlier, it’s preferable to
run the largest diameter pushrod that
the engine will accommodate. This
helps to reduce deflection and increase
valvetrain stability. That doesn’t mean
that you necessarily should move from
a stock 5/16” diameter to a 7/16”
diameter. Today’s pushrods (by the
quality manufacturers) are comprised of
Rocker arm adjusters are available in a variety of cup and ball configurations in terms of diameter
and radius. Adjusters should always be harder than the pushrod rocker tip. (courtesy Trend)
74 JULY-SEPT 2018 engine professional
BY MIKE MAVRIGIAN
Car may feature solid tool-steel with no Correct pushrod length is key in obtaining a center
oil passage to the ball stud through the contact sweep of a roller lifter to the valve.
pushrod body, a 3/8” ball at the lifter
end and a 3/8” cup at the rocker end, in
diameters of 716” or ½”, hardened to
54 to 56 Rockwell C.
Pushrod diameters and wall
thickness obviously play a major role
in stiffness and resistance to deflection.
However, body diameter is much more
crucial as compared to wall thickness.
Regardless of the application, the rule
of thumb is to run as large a diameter
as possible, given the clearance confines.
While 5/16” diameter may be suitable
for a mild street application, as factors
such as compression, RPM and spring
pressures are increased, the need
increases for greater pushrod diameter.
Diameters ranges include 5/16”, 3/8”,
7/16”, ½”, 9/16” and 5/8” and in some
extreme cases, even ¾”.
As noted earlier, it’s preferable to
run the largest diameter pushrod that
the engine will accommodate. This
helps to reduce deflection and increase
valvetrain stability. That doesn’t mean
that you necessarily should move from
a stock 5/16” diameter to a 7/16”
diameter. Today’s pushrods (by the
quality manufacturers) are comprised of
Rocker arm adjusters are available in a variety of cup and ball configurations in terms of diameter
and radius. Adjusters should always be harder than the pushrod rocker tip. (courtesy Trend)
74 JULY-SEPT 2018 engine professional
