Camshaft thrust plate C9OZ-6269-( ) variations for HiPo 289 after L7 change

[6s1640]

Hi all,

I was doing some research on the cam bearing thrust plate and learned there are three variations for the HiPo 289 change L7 and after.  The difference is the thickness.  They are:

Standard .250

.002 Oversized at .252

.004 Oversizde at .254

Please help me understand why the three sizes.  Does it have to do with the alignment of the cam timing chain gear to alignment to the crank timing chain gear?

How do you determine which size is needed?

The before L7 change HiPo 289 gets a .375 thick thrust plate.  You don't want to mix these up.

Thanks

Cory

[OldGuy]

Cory, the reason for more-than-one thrust plate thickness is to establish thrust end play of the cam/thrust plate/sprocket assembly when installed in the engine. The factory manual states that the end play should be between .001-.007". The varying thrust plate thickness's are utilized to accommodate the manufacturing tolerances of the protruding hub length on the cam sprocket. Determining which sprocket is correct for a particular engine is done empirically by starting off with the thinest trust plate (.250) and assembling the cam/thrust plate/sprocket in the engine. Measure the end play (by prying the assembly forward axially) with a feeler gauge. If it is within specification, your done. If it exceeded the factory spec., select a thicker thrust to establish the recommended clearance.

I hope this answers your question.

Frank

[6s1640]

Cory, the reason for more-than-one thrust plate thickness is to establish thrust end play of the cam/thrust plate/sprocket assembly when installed in the engine. The factory manual states that the end play should be between .001-.007". The varying thrust plate thickness's are utilized to accommodate the manufacturing tolerances of the protruding hub length on the cam sprocket. Determining which sprocket is correct for a particular engine is done empirically by starting off with the thinest trust plate (.250) and assembling the cam/thrust plate/sprocket in the engine. Measure the end play (by prying the assembly forward axially) with a feeler gauge. If it is within specification, your done. If it exceeded the factory spec., select a thicker thrust to establish the recommended clearance.

I hope this answers your question.

Frank

Hi Frank,

Thank you for the reply.  What you are saying makes perfect sense.  What is still confusing me is the plate is flush on the cam side of the plate.  I don't understand how thickness can adjust the end play.  More help needed.

Is the end play controlled by the space between the sprocket and the plate?  I can see how a thicker plate would work then.

Thank you

Cory

[OldGuy]

Cory, I'll try to explain it without the benefit of pictures or diagrams. So bear with me.

The back face of the thrust plate rubs on the face of the cam-thus limiting its travel forward. Assume that the thrust plate is .250" thick. Also assume that the protruding hub on the sprocket (rear side) measures .255" from the SPROCKET thrust face to the aft end face of the sprocket. When all components are assembled, the aft sprocket face butts up against the forward face of the cam. In THEORY, there should be a total of .005" movement (or "clearance") that the cam/sprocket assembly can move forward and aft. If there were a .252" thick thrust plate installed, that total movement would be .003. If a .254" thick thrust plate were installed, the total movement would be .001". In other words, if the thrust plate thickness was subtracted from the sprocket hub thickness, you will get the theoretical "clearance" between the forward face of the thrust plate and the thrust face of the sprocket, i.e. .255" - .250" =.005".

Remember, all of the above is theoretical. ACTUAL measurements (as I outlined in my first post) can vary.

Frank again.

[6s1640]

Hi Frank,

Thank you for the explanation.  I now understand.  The aft face of plate controls forward movement with the cam forward face butting up against the plate.  The aft face of the sprocket controls the afterward movement.  The cam timing chain gear, sprocket, has two surfaces.  One that contacts the forward face of the cam., bolted tight.  There is a secondary surface on the sprocket face that has the clearance to the forwards side of the plate that you mention.  I now understand.  Sorry for my slow learning.

Thank you

Cory

[OldGuy]

You're all set. I glad I could help/

Frank

[gt350hr]

    Cory,
       To add a bit to Frank's excellent reply , limiting camshaft end play is important because the cam and lifter "relationship" must be maintained or lobe/ lifter wear will happen. Another reason is back and forth movement affects ignition timing too and could cause cam or gear wear at the same time. To get a little more technical , cam lobes are ground with taper to keep the slightly crowned lifters rotating. exactly half of the lobes are tapered in one direction and the other half in the opposite direction. This combination balances the forces for zero "thrust" so to speak. The thrust plate could also be described as a cam retainer because of that. Reality is that there is a small amount of fore and aft movement which is limited by the clearance between the gear, cam , and plate relationship. I have had situations where clearance is excessive  (well , out of spec anyway) and I had to sand /surface the "hub of the gear ( that contacts the cam) to attain the proper clearance . FEW if any people check cam end play and "most" get away with it. Others have mysterious dist gear failures or timing fluctuation. Like I said just a little more information.
     Randy ( another "old guy")

[pbf777]

     Reality is that there is a small amount of fore and aft movement which is limited by the clearance between the gear, cam , and plate relationship.

    But, generally this intermittent and mostly self cancelled thrust value as accurately described from the lifters being ramped up the angled camshaft lobes is greatly masked by the more constant rearward (in relation to the engines relevant in this forum) thrust created by the oil pump and its' drive geared to the camshaft.  This is generally witnessed of used components taken out of service with the greater evidence of wear to the thrust-plates' forward face and the timing gear sprocket's rear thrust face. 

    As an additional example, (though to early for relevance to this forum, but still of Ford Motor Co. manufacture anyway), would be the early ('58 - '62) FE's which did not utilize a cam-thrust-plate, rather the camshafts' nose consisted of a flange with a rear facing thrust surface which acted against the blocks' forward face and aided with a spring loaded "button" against the timing cover.  This engineering demonstrates that the major thrust in this application is rearward and only a minor concern exists in the forward direction; the overriding value being supplied by the load incurred in driving the oil pump.   

    Scott.