F-134 Camshaft End Play

[JohnK]

I am using the service manual, Ludel’s rebuilders manual, and Eric Lawson’s thread on the 3b info page.  Camshaft end play is driving me a bit nuts.  I’ve become pretty familiar with the gears and related components as I must have installed and removed them 5 times.
 
I’m a bit stumped on the camshaft end play.  The spacer is .006 thicker than the thrust plate as it should be.  So, I install the thrust plate and now the camshaft forward movement is limited by the thrust plate.  Now all resources I’m using say to install the cam gear using the bolt to draw onto the shaft and secure at 35 fp.  Well now the rear gear face is up against the spacer which limits the rearward movement of the shaft – end play now equals 0! The manual says to measure the end play as .006 between the rear face of the gear and the thrust plate.  Well of course that measurement is .006 because that’s the difference between the thrust plate and the spacer.!! 
I’m sure I’m missing something hear but I thought that maybe I should back the cam gear off and draw it back on while measuring the end play and stop when the end play is within the spec.  But that begs the question of torquing the bolt – do I put a feeler gauge in between the rear gear face and spacer while tightening?  That just doesn’t seem right either – I’ll probably rip the feeler gauge trying to pull it.
Interestingly, I don’t even see a place to buy cam shaft shims if I did need them.  I certainly appreciate any advice – I’d like to move on to the pistons and valve train.

[JohnK]

Bump

[Rus Curtis]

Maybe just me but I can't see any message/image in the first post, i.e. blank.  I do see the "Bump" text.

[Bruce_W]

  It's there for me, but I don't quite understand your problem. I mean, I understand that 0 clearance is a problem, but I don't understand why you're having that problem. I guess I need to go dig out a cam, a spacer and a thrust plate and see if I can visualize your problem.  BW

[oldtime]

Well it seems to me that you possibly installed a new replacement camshaft or camshaft gear of questionable quality.
If the camshaft or gear hub dimension is off then that could feasibly effect the end play after they are torqued.
I suggest you locate some appropriate sized shims so the camshaft gear does not pull so far onto the camshaft.
Or you could feasibly sand .005 or .006 off from the thrust plate thickness.
Do make sure that the gear is torqued down to spec.

Got that ?

[JohnK]

Rus - I "bumped" to bring the topic back up to the top.

Oldtime - Got it.  You are correct. I am working with a newly machined replacement block.  The camshaft from the original block had a serious defect on one of the cams.  I am using a different (used) camshaft that I have.  In my search for a suitable replacement block, I ended up with 2 blocks- I had the best one machined.  The camshaft I'm using came from one of those two.  The camshaft gear is new (almost) as it came from the original rebuilt engine. The spacer also came from the original engine.  I will check the spacer, camshaft gear hub, and also locate some shims.

Thank you for your response.

John

[JohnK]

This is the first time I've rebuilt an engine from the ground up and faced these endplay issues.  What appears to be unsaid in the all the resources I'm using is that torqueing the combination of gears and pulley (crank) should result in proper endplay tolerances.  Offhand, my inexperienced opinion says that is strange.  However, further inspection revealed the following:

Notice how that washer is cupped - that definately doesn't seem right.  The pully also isn't fully on the camshaft at 0 endplay - seems odd as well.

[oldtime]

The gear washer is supposed to be cupped because it acts like a spring.
So that is perfectly normal.

[JohnK]

when the bolt is torqued - should the washer remain cupped, go flat, or invert.  mine seems to go to inversion.

[oldtime]

Best I recall they stay cupped but tend to flatten out a little.

[JohnK]

I think that second picture is telling me something. The gear isn't even on fully, yet the backside of the gear hub is up against the spacer.  Time for some measurements on the old and replacement cams.

[JohnK]

Well I've removed the cam from the engine block and removed the cam gear - again!  There are no discernible differences between the old and replacement camshafts that would create this problem.

From the service manual:

"End play of the camshaft is determined by running clearance between the rear face of the camshaft gear and the thrust plate.  The standard clearance is .004" to .007" as measured by a dial indicator.  Should a check show too little end play, place a shim of suitable thickness between the camshaft shoulder and the spacer.  Too much end play may be corrected by removing shims of dressing off the spacer a slight amount. "

The picture below shows my installed camshaft with the spacer in place.  The spacer is exactly .006 thicker than the thrust plate. When the gear is installed to let's say .007 running clearance (again between the hub and the thrust plate) then the hub would be .001 off the spacer.  So the most the shaft could move rearward for end play would be .001. 

So perhaps I am misunderstanding how one would use a dial gauge to measure the end play.  .007 end play as defined would mean a reading of .001 on the dial gauge.  .006 end play would show 0 on a dial gauge because the thrust plate prevents any forward movement and with the hub up against the spacer there would be no rearward movement either - so what use is the dial gauge.

I'm guessing this -when they are describing this "end play" running clearance, it doesn't really mean the distance that the cam can travel back and forth but instead, as described above the clearance between the hub and the thrust plate.  I think this is where I'm having my problem - I'm thinking camshaft travel and that is incorrect.  This is really about the thickness of the spacer and that thickness relative to the thickness of the thrust plate.

Having thought about this so much I think I now understand what this is about - you don't want that rotating hub rubbing against the fixed thrust plate but instead to rotate against the spacer which is not fixed and can spin on the shaft.  So given that the difference between my thrust plate and spacer is .006, that means that I should have no more than .001 travel as measured by a dial indicator.  I would think that you also don't want that hub to be up too tightly against the spacer creating friction but than again maybe the friction would likely cure that pretty quickly- (or create a catastrophic failure for all I know  )  Of course, the question arises - the bolt should be torqued to 35 fp - what if it only take 20 fp to move the gear?

If I'm correct - the starting point of this procedure should say - use a caliper to determine the difference between the thickness of the thrust plate and the spacer, this sets the minimum running clearance you have-less than .004 than add shims, more than 007 then dress the spacer.

At this point, I think I should install the gear until I get a dial indicator reading of .001 putting me at the max end of the end play / running clearance.  So my process should be to set up the dial indicator as I install the hub, checking end play travel until I get to .001.  I do find it interesting though that when installed the cam gear hub is not fully on the shaft as shown in my picture in the prior post.

I appreciate any advice on my missive - i really don't want to install / remove the camshaft and camshaft gear for the 5th time.  It's a pain because I can't remove the gear with the camshaft installed because I've found no puller with arms that can properly grab the hub in such a way to not shatter the gear with the cam in place.  And I'm using up all my assembly lube!.

[oldtime]

Don't confuse things... .006 end play measures .006.
Your camshaft should have correct end float within the specs given.
Torque the gear down to 35 ft pounds as stated.
Forget about the thickness difference between your thrust plate and spacer.
Just add some round shims (about .005) under the spacer and get the end float to read .005 or so.

Or else you could sand the thrust plate down about .005".
It's perfectly acceptable to sand down the bronze thrust plate especially if it has any mild gouges upon it.

[JohnK]

It is hard to not confuse things when you are confused.

Section D-53 of the service manual:

"End play of the camshaft is determined by the running clearance between the the rear face of the camshaft gear and the thrust plate and is established by the spacer thickness.  The standard clearance is .004 to .007 and can be measured by a dial indicator.  As a general rule this clearance will change but little through wear or when a new gear is installed.  To predetermine the correct end float with the gear, spacer, and thrust plate removed, measure the thickness of both the thrust plate and the spacer with a micrometer.  The thickness of the spacer should be approximately .006 greater than that of the thrust plate.  When this is correct and the parts are assembled and drawn tightly together by the gear retaining sccrew, the end play should come within standard limits".

My spacer to thrust plate difference is .006 exactly.  When I draw the gear onto the shaft and tighten to torque spec - a dial indicator shows 0 end play. - four times over I have done this procedure resulting in zero float each time.  This is where I am confused - as you see from the prior post picture, the gear hub is not completely on the shaft when torqued down and no float is shown by the dial indicator. Obviously, the torquing of the gear sccrew (bb software won't post the correct spelling) continues to push the gear further on to the shaft until the hub is fully against the spacer.  Hence no end play float - the plate stops outward movement of the cam, while the gear prevents inward movement.

Take a look at the picture below noting the rotary scuff marks on the cam facing side of the hub - this is a new gear with less than an hour of running time on the engine.  ( again for those unfamiliar with my embarrassing end to a years long rebuild - yes I cracked the block on a freshly rebuilt engine (not by me) after less than 1 hour running time).   During the tear down of the old block, I have identified some disappointing discoveries of a less than professional rebuild.  I suspect the scuffing shown is likely due to improper engine plate bolts used rather than camshaft end play.

So according to the service manual my thrust plate and spacer are perfect and I should be able to torgue it all down and all will be well - 
with the exception that a dial gauge measurement referred to by all the manuals and OT shows zero end play.  Could I have an incorrect cam gear that has too wide a hub?  Maybe someone has a gear they could measure for me?  but a look up shows it to be a Cloyes 2900 - Fiber Timing Camshaft Gear that should be correct.

Please forgive me for beating this subject to death and my unabated confusion. But after 10 years of money and many, many long hours - I want to be able to drive the willy's and not be back removing an engine for the third time, and rebuilding it for the second.

Oh and finally, I haven't seen anybody selling camshaft shims.

[oldtime]

IMG_1947.JPG (2808.29 kB, 3264x2448

The foreward edge of gear hub can extend out from the end of crankshaft.
The aft edge of gear hub  must be seated against the spacer /shims.


IMG_1949.JPG (4657.54 kB, 3264x2448
Yes that certainly appears that the thrust plate bolts were rubbing.
Either too thick of heads or use of lock washers could feasibly cause that.

So according to the service manual my thrust plate and spacer are perfect and I should be able to torgue it all down and all will be well

Yes I agree.

I'm not sure yet what the problem is.
I've never seen this before.
Be patient and I'll try to figure this out.
You simply can't run it with zero camshaft end play.

So is the front of the block perfectly flat , including the area where the thrust plate bolts down ?
Is the thrust plate perfectly flat and smooth or does it have mild gouging / striations ?