Friday, June 26, 2015

Camshaft Endfloat and Timing Cover

<This post is part of the 'New Engine Rebuild' project>
You would have thought that setting the camshaft endfloat would be a fairly straight forward affair. All other parts of the engine I have encountered so far where endfloat is critical, could simply be shimmed up to eliminate the slack and get things into tolerance. For some reason though when it comes to the camshaft endfloat, I couldn't find any shims at all to help me out. So how exactly do you make sure the endfloat is correct??



Measuring.
The task is to work out how to measure the endfloat in the first place. For this, I attached a new triangular thrust plate over the cam and put the larger timing gear in place and torqued it up to the necessary 88Nm.

Nice new thrust plate
As I don't have the water pump on at the moment, it gives a handy place to mount the magnetic stand of my Dial Gauge. Pressing the timing gear in as far as possible, I set the plunger of the dial gauge on the face of the large gear and zeroed it.


Now pulling the timing gear in and out by hand, I can use the gauge to see how far it's moving back and forth. There's a distinct tap sound as the camshaft is flipped in and out and the first measurement I got was 0.25mm. Looking at the spec though, that's way out!!!



Understanding
So the question is, how can I correct the endfloat and get it back into tolerance once more? To do that though, I need to wrap my head around what determines the endfloat in the first place. So after a bit of googling and playing with some spare parts, I found out that it's down to two factors...

The first is the thickness of the triangular trust plate and of course how worn it gets...



The the second is how deep the boss is on the large timing gear.

Large Timing Gear Boss
In the picture below, I have positioned an old thrust plate over the boss and the gap that can be seen represents the endfloat that would be created if I were to use these parts (plus whatever wear is scored into the thrust plate).



To understand it further, I created a 3D model of the parts using SketchUp. Slotted the parts together in the model, it becomes more obvious where and why the endfloat occurs.



Correcting
So now that I understand what controls the endfloat, I know that one of two things will sort it out. Either a thicker thrust plate, which is clearly not an option as they are only sold in one size, or work out a way to remove the necessary amount of metal from the boss on the large timing wheel.

After overthinking how to achieve this for days, I eventually went for the easiest and simplest option of placing some emery paper on a flat surface and slowly move the timing gear back and forth to grind away at the boss.


I found that be rubbing six to seven times in the same direction and then rotating and repeating, it was relatively easy to grind the metal away nice and evenly all round.



Through a process of grinding and test fitting, I managed to eventually remove just enough material to get the endfloat exactly where I wanted it, at 0.08mm or about 3 thou.


With that set, I checked the timing gears were aligned...



Once I was satisfied that they were okay, the chain was mounted and the camshaft nut torqued down one final time and the lock tab bent over. I had to look on old photos I took to work out which way the oil thrower went and it looked to be concaved part facing the engine.



At this point, I checked the valve timing again using the same method as before and thankfully it hadn't altered from when it was last set. After cleaning the gasket surfaces with meths, I used a new gasket and some RTV and attached my rather nicely refurbished timing cover.




The last thing to go on was the lower pulley, lock washer and bolt which was torqued up to the necessary 102Nm.



Once the lock tab was bent over the job was done and I could stand back and enjoy the rather fetching black and red 80's vibe the engine seems to have taken on now!





<Next Post> - 'Oil Pressure Relief Valve'
<This Post> - 'Camshaft Endfloat and Timing Cover'
<Previous Post> - 'Electrical Gremlins and Melty Cables'

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