Rocker Shafts & Bushing Kits
By Stephen Kassis
A very common wear item on early Chevrolet engines is the rocker arm assemblies. Early engines did not have a good oiling system for the top end and, consequently, the shafts & bushings tended to wear out. There are reproduction and aftermarket rocker arm repair kits available to help with this kind of repair.
After 1931, Chevrolet did not offer separate bushings for rocker arms. The reason for this was that the bushings for 1932 were so thin that they must be installed in the rocker arm BEFORE the oil groove was cut into the bushing. Some NORS shaft & bushing sets have oil grooves, however, none of the reproduction rocker arm bushings come with grooves. As part of the installation of these bushings, a groove must be cut into the center of the bushing for oil flow to the weep hole at the top of the rocker arm. Failure to do this will cause a lack of oil at the valve stem or pushrod tip.
After removing the original bushings, press in the new bushings into the rocker arms. Bushings that have oil grooves will also have holes for oil passage. It is important that the oil passage holes are lined up with the holes in the rocker arm when installing the bushings. On bushings without holes, drill a hole through the bushing, using the weep hole as a guide. Use a drill that is the same size as the weep hole. Note: 1929-31 models use an oil wick to feed oil to the pushrod tip. Replace these wicks when rebuilding the rocker arm assemblies.
For bushings without grooves, cut a shallow groove in the bushing, all around the center of the bushing. One method to do this is using a Dremel tool with a flat cutting disk. Cut most of the way through the bushing but try not to go all the way through. A lathe or milling machine would be the preferred method if you have access to one. The groove needs to be at least the width of the oil weep hole, but slightly wider wonât hurt.
Once the groove is cut, use emery cloth to remove any rough edges and fit the rocker arms to the shafts. Be sure to oil all bushing surfaces prior to assembly.
1932-1934 rocker shafts should have original shouldered bolts holding the rocker shafts to the rocker stands. There are four of these bolts. The reproduction shafts we provide will not allow for a shouldered bolt, so these must be changed. These are not a hardened bolt, so they should be available at an auto parts or hardware store. Purchase bolts with no shoulder that match in length and size to your originals.
CAUTION: When installing 1932-1934 rocker arm shafts, INSURE THAT THE OIL HOLES ARE ON THE BOTTOM. Failure to do this will cause poor oiling to the bushings and therefore, premature failure of the bushings. 1929-1931 rocker shafts have oil holes at the top and bottom and can be installed either way.
Check the rocker arm adjusting screws when rebuilding the rocker arms. Remove each adjusting stud completely from the rocker arm. Check the threads carefully as these can break off and cause the adjuster stud to lock or move after being adjusted. Replace any adjusters with broken threads.
Last, but not least, check the tip of the rocker arm where it meets the top of the valve. This is a common wear area as lack of oil usually causes severe wear. If there is âcuppingâ at the rocker arm tip, it must be resurfaced until it is smooth. If this is not repaired a proper adjustment of the rocker arms will not be possible. Feeler gauge readings will be inaccurate. Distortion to the feeler gauge will be noted with impressions of the worn area transferred to the flat metal of the gauge. In these cases it will be necessary to build up the tip of the rocker by welding with a hard material like Stellite. A machine shop can then grind the tip smooth while keeping it slightly rounded
. A properly rebuilt rocker arm assembly will have snug fitting bushings on a smooth shaft. It will also have good oil flow to the rocker arm bushings, pushrod tips and the ends of the rocker arms that push on the valve ends. Lack of oil at these spots will eventually cause problems
. Related Parts: FS-251, FS-954, FS-954A, FS-75, FS-68, FS-498, 838244, RW-25, 364912, 837365, 839304