- In this module we're going to have a practical demonstration of how
we can use feeler blades to measure clearances on engine components.
In front of me I have a standard set of feeler blades.
If we open the feeler blades up we can see that we have a range of hardened
steel blades.
On each of the blades we have the measurement or thickness of that
particular blade.
The measurements are listed in both metric as well as imperial units
depending on what you're happiest working in.
Now one of the problems when it comes to using feeler blades is a certain amount
of feel is required as to what sort of resistance is expected.
If we use a feeler blade that is too thin for the clearance that we're measuring,
there's going to be no friction or resistance when we slide the feeler blade
through the components we're measuring.
On the other hand if we choose a feeler blade that's just slightly too thick,
we may be able to force it through the components we're measuring,
but there will be a lot of resistance.
So some of this requires some knowledge of what we're expecting.
Now a really good way of developing a bit of a feel for what is normal or
correct when we're using feeler blades, is to do a test with a couple of glossy
magazines and a sheet of paper.
So I've got in front of me here, two glossy magazines,
I've got a normal sheet of A4 printer paper, and what I'm going to do is put
the sheet of A4 paper between the two glossy magazines,
I'm just gonna hold down on the corner of the magazine and I'm just going to
gently pull the sheet of paper out.
And that's going to give you a good guide as to what the normal amount
of resistance should feel like.
Now if you go too large in your feeler blade there's gonna be a lot more
resistance.
If you're too small in your feeler blade there's going to be minimal to no
resistance.
Now we know what we're looking for, let's actually have a practical example,
and we're going to measure the valve lash clearance on a Toyota 1FZ
cylinder head.
So on this cylinder head what we're going to do for our demonstration
is we're going to measure the exhaust valve clearance here on number one
cylinder.
And what I'm going to be doing is sliding the feeler blades between the base
circle of the camshaft lobe and the bucket that the camshaft lobe sits on.
It's relatively typical to expect somewhere in the region of about
10 thousandths of an inch clearance on this sort of mechanical valve mechanism,
when the engine or cylinder head is cold.
So let's grab our feeler blades and see what we actually have.
What I'm going to do here is start by using my 10 thou feeler blade.
And what I want to do is simply slip the feeler blade or the end of the feeler
blade between the base circle of the camshaft and the top of the bucket
or lifter, so we're just going to push this through.
And now I can feel there's absolutely no resistance.
It's just sliding straight through there, and this indicates straight away
that 10000ths of an inch is too small in terms of our feeler blade.
So what we're going to do is just jump up in size.
I'm just going to open up our feeler blades and the next size I'll try here
is our 12 thousandths of an inch blade.
So we're just going to do the same procedure there.
Now with my 12 thousandths of an inch blade, I can now feel a reasonable
amount of resistance so this indicates to me that I'm probably pretty much
correct with the 12 thou feeler blade.
In order to just confirm this though, what I will do is I'll try going a little
bit wider and we'll just open out our 13 thou feeler blade and try
pushing this between the cam and the bucket.
And in this case I cannot force, well I would need a reasonable amount
of effort to force this feeler blade between the cam and the bucket.
So I'll go back and we know that in this case, 12 thou is
the correct clearance.
Like all of the tools we're looking at in this course, learning how to use feeler
blades correctly is going to take a little bit of practice.
But once you've used them a few times, you're quickly going to get a feel
for what sort of resistance you're looking for when you're trying different
feeler blades to check your measurements.
That was just one of the modules from the engine building fundamentals course,
which is the perfect starting place if you want to learn how to assemble high
performance engines.
This course will teach you about engine anatomy, essential engine machining
processes, how to select and measure critical clearances in your engine,
how to assemble the engine long block, and how to break in your fresh engine.
For more information and to purchase the course, click the link now.