Are you sick of the clackity-clack clack clack valvetrain noise that steel pushrods give you when the engine gets hot? SO WERE WE! That's why we designed these aluminum pushrods to assure that the valve clearance is constant regarless of temperatures (PR expansion is the same as stock)!We successfully use these even on VW Dual Valve Spring equipped engines, with ratio rockers, up to 9500 RPM! These are over 3X stronger then the other Aluminum "HD" pushrods available (which we stopped selling due to failures). Run these at .006", same as stock, which will give you .002" when hot. These are the proper length to install Bugpacks great 1.25 Ratio Rocker Arms (4019-20) onto your engine, IF you had original length PRs to begin with.
These 3/8" 2024 T-3 heat treated .095" wall thickness pushrods are good to 400-500 lbs of spring pressure for you guys with HUGE valves and valvesprings! Get the benefit of proper expansion and quiet running in a pushrod that can handle almost any valves, RPMs, and springs that you throw at it!
We have found the spring pressure limit of 400lbs with 1.5 rockers and 8200 RPM (straight PRs), and no limit yet on the dual tapered design. If you use less spring, less rocker, or less RPM you'll be fine.
One main reason for running these is to reduce valvetrain mass so you can drop spring pressure, so don't go nuts on the spring pressure!
WARNING: These steel pushrod tips are case hardened .012-.015" deep to a 60-62 Rockwell on the C scale (that means they are HARD). YOU must check them for smoothness, and MAY have to smooth them (polish) with some fine emory or sandpaper prior to installation for best results.
Valve lash is critical on aluminum pushrods. It is possible to have a pushrod failure even though you haven't exceeded our RPM or spring pressure limits, and this is always due to excessive valve lash. If your valve lash gets over .010", the tips of the pushrods WILL get pounded into the pushrod. This is not a problem if your valve clearance is the way it's supposed to be, but a swivel foot failure, or loose valve adjusting screw, can cause excessive lash which can ruin these pushrods quickly.
WEIGHT: For reference, in a 11.600" length, the weight of a stock pushrod is 39.1g, ACN HD Aluminum are 47.8g, ACN Dual Tapered HD Aluminum is 55.8g, Manton Chromoly Straight are 90.2g, and Manton DT Chromoly are 100.5g.
The straight pushrods have an OD of the pushrod body of 3/8" (.375") for those concerned with pushrod tube interference. For reference, the stock pushrod is 10.935 inches long on the 1300, 1500, and 1600 engines. Before you make the jump to Aluminum pushrods, be aware that valve tapping can be caused by valve lash, AND ROCKER ARM SIDE PLAY. Make sure your sideplay is tightend to .005", a loose rocker (side to side) will sound just like a loose valve adjustment. IMPORTANT: Measurements given are TIP TO TIP measurements (tips installed). And you cannot return pushrods that you have been cut and assembled! These pushrods have a counterbore, so get the shortest pushrod that is longer than you need.