:idea: About distributor gear wear (UPDATED!!)
Here is a list of things that can cause distributor and cam gear wear.
1. Oiling holes throught the large timing gear, the groove for the oiling hole must be at 2:00 from the keyway, also all passages must be clear.
2. Cam bearing at the front of the block must have a groove in it, this sends oil through the cam at all orientation and rotation of the camshaft.
3. The cam must have a 90 degree oiling hole setup to feed the timing gear and must be free from casting obstruction.
4. Cam gear must be matched to the distributor gear. Their are 2 types of cam gears out there and at least 3 types of distributor gears, they CANNOT be mismatched, replacing just the cam gear will cause big problems.
5. The timing cover: The oil pump drive gear's shaft that connects to the distributor goes through a hole in the timing cover, this is a precision hole and if tapered can cause distributor gear wear through chatter.
6. Oil pump gears: Using longer than stock or poorly made after market gears can cause chatter, binding or premature wear of the oil pump drive gear's shaft hole. When you install a aftermarket kit that comes with new gears the idler gear pin MUST be longer. The cam and distributor gears are only rated at a certain torqueload. Some of the new gears available as of 4-22-05 are now hardened (both gears) and can withstand greater pressures
7. Oil filter.......Yes oil filters can cause premature dizzy and cam gear wear. If you run the wrong oil (too heavy) or a filter that gets clogged early or a filter that isnt a high flow you open up your oil filter bypass and not only send dirty oil through your motor, you also exerpt a high amount of pressure on the oil pump and that alone can cause gear wear, this happens mostly on start up. In late 87 chrysler got rid of the oil filter bypass on the oil filter adaptor, after market oil filter adaptors also have this cast in. Beware that if you use a high pressure oil pump spring without a oil filter bypass you run the risk of ballooning your filter.
8. Cam walk: Cam walk can be attributed to a cocked or poorly place cam plug (large freeze plug that hold the cam from leaving the rear of the block. Also cam walk can be caused by bad lifters, worn cam bearings, cam bearings installed improperly, or a poorly ground cam and in some cases a new cam that gets flattened on startup
9. Cam walk can also be attributed to lack of relief holes in the back of the cam, you see pressure can increase between the end of cam and cam plug, most of these cam must be checked, we have 3 in here with no relief holes...............dang summit
10. The retainer washer for the front of the cam that holds the distributor gear must also provide a positive seal for proper oiling. Off the shelf washers can sometimes have nicks or be convex or concave which to factory torque specs can lead to a loss of oil in front of the camshaft.
11. The installation of the timing cover without locator pins or worn location holes will cause a mis-orientation of the thrust on the distributor gear and eventually may result in a broken or heavily worn set.
12. Early Crown timing covers that were not checked for proper dimensional tolerance can attribute to up to 100% of the fast gear wear. Even today vendors should check for proper alingment.
I have seen a AMC V8 go 210,000mls without any cam walk and very little gear wear. I have also seen a AMC V8 go 2 miles and eat the gears. The factory engineers knew all this and they put these motors together accordingly. Building a AMC V8 can be a expensive build and its a dirty dirty shame to have something like a cam or distributor gear go out, this can cause Major scoring on the oil pump cavity and also can cause the oil filter bypass to open and voila, roached bearings. Hope these hints help anyone out who is building a AMCV8.
-MC
