Distributor Gear CompatibilityIf you’ve experienced excessive wear of a camshaft distributor drive gear, and maybe had to replace either the cam or the distributor drive gear itself, here’s some good information you’ll want to retain. Crane Cams roller tappet camshafts are ground on 8620 billet steel cam cores that are heat treat hardened to resist wear.
This 8620 steel billet material is wonderfully tough stuff, but it can also be very hard on distributor gears! To remedy this, Crane 8620 steel billet cams MUST use a high silicon copper alloy distributor gear, to prevent rapid wear of the camshaft’s distributor drive gear. These are usually referred to as “bronze” gears.
Cast iron hydraulic or mechanical tappet cams are also susceptible to premature wear of the camshaft distributor drive gear or the distributor gear itself. This problem, when it occurs, is usually accompanied by the use of a high volume oil pump in a stock or mildly modified engine.
Cam gear or distributor gear wear is usually NOT caused by the high volume pump itself, but by insufficient internal engine running clearances.
Chevy V-8’s, small block, big block, and 90? V-6 engines, all use splash lubrication to oil the distributor gear. Although higher RPM operation provides sufficient lubrication to prevent wear, low speed use can be a problem. The situation can become critical if a high volume oil pump is used. The high volume oil pump was developed for engines where bearing clearances were increased over stock. These work fine in racing engine applications, where extra clearance is provided in the short-block.
However, when a high volume oil pump is used in an engine with stock internal clearances, the increased volume of oil can’t flow through the engine fast enough to relieve the back pressure created. This places an increased load on the distributor gear, and leads to accelerated wear.
Once the gear on either an 8620 steel cam or a cast iron cam is worn excessively, the cam itself must be scrapped! There is no repair for this problem, and the only option is to buy a new cam. To eliminate this annoying and expensive problem, we offer a simple, do-it-yourself way to help oil the distributor gear and reduce this accelerated wear in Chevy V-8 and 90? V-6 engines.
On these engines, the lower portion of the distributor housing drops through the oil gallery that supplies oil to the lifters on the passenger side of the engine. Two rings at the bottom of the distributor housing seal the top and bottom of this galley. Oil flows around the distributor, between the two rings.
Solving distributor gear wear is as simple as filing or machining a .030″ groove in the bottom ring of the distributor housing. A three cornered file can also be used.
The distributor housing should be grooved in any engine operated for extended periods at low engine RPM. With the distributor installed in the engine – ready to run – the groove should face TOWARDS THE CAMSHAFT. This will provide a reasonable flow of oil to lubricate and cool the distributor gear and cam gear as they operate.
Remember to keep the groove facing the camshaft, and be sure to use the correct Crane high silicon, copper alloy distributor gear for best results.