Cam Shim?

[Backtanner]

I recently pulled my Mallory Dist. out of my 454 to discover that the teeth were totally shot. I'm told that the cam will walk forward at times not allowing the teeth to mesh 100%. Even though I've never heard of this, it makes sense and I want to prevent the same to the MSD recently installed.Question here is how to prevent this from happening again.
[ September 21, 2002, 06:12 AM: Message edited by: Backtanner ]

[Clown]

The problem starts like this.
Is it a steel gear or a bronze gear on the dist?
The installed height of the dist could be off.
Or the cam could be walkin.
Do you have a cam button in the timing chain cover
this keeps the cam from walkin.
If it is a roller cam they can put two different type of gears on it "One being a soft one for a steel gear" And the other a hard for the Bronze gear.
If you run a hard gear on the cam and a steel gear on the dist This kinda thing will happen.

[Backtanner]

The gear was steel as far as I know. I thought there was only one installed height for the dist (flush with the intake), unless there is some kind of hokey oversized gasket. I remember a friend of mine mention a type of wear plate that would mount in front of the cam inside the timing cover.Is this the "cam button" your talking about?And it's not a roller cam.

[Dennis Moore]

The camshaft drives the oil pump through the distributor gear. If you have an oil pump that is hard to turn you will wear out the dist. gear quickly. High volume/high pressure oil pumps with thick oil will also wear out the gear quickly. Check it out!
Dennis Moore

[MandDPerformance]

Distributor installed height changes from engine to engine and there are many different reasons. Intake manifolds, deck height, head gaskets, and intake gaskets, "just to name a few" all can have an effect on the distributor installed height. What's important is the amount of engagement of the distributor drive gear into the oil pump shaft. You also need to make sure that you do not bottom out your distributor in the drive gear or block. Install your dist. without the gasket first to check clearances and shim accordingly from there. It is not uncommon for a thicker gasket, or multiple thin gaskets, to be used to insure proper install height.
As far as cam shims are concerned there are many different types. The main purpose of the shims is to adjust cam end play. You can install a thrust bearing shim kit to minimize friction and endplay but a lot of times you may need to machine the front of the block in order to keep the cam lobes where they belong. Less endplay means less gear movement and more consistent driving of the distributor and oil pump. Your timing will be more accurate with the right gear and cam endplay combination. Your flat tappet cam will use a steel distributor gear. Check out the old one and observe where the wear pattern is on the gear and the engagement depth of the oil pump drive shaft.