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How to Degree a Cam: How to Fit and Use a Dial Gauge

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How to Fit and Use a Dial Gauge

10.02

00:00 - When it comes to accurately measuring our valve or cam lift, we're going to need to fit a dial indicator to our engine.
00:07 And while we've already briefly looked at the dial indicator in our module on finding true top dead centre, in this module we're going to delve in a little bit deeper and we're going to see the correct techniques for fitting the dial indicator and setting it up to measure valve lift on our Honda B18C.
00:23 Now of course there will be slight differences from one type of engine to another but the fundamental principles are going to remain the same.
00:31 When it comes to our dial indicators, these are available in either metric or imperial and you can choose either based primarily on what sort of engine and what sort of components you're going to be using.
00:43 Of course we can still convert between imperial and metric units if we simply remember that there are 25.4 millimetres in one inch.
00:51 So if you are using a metric cam card with an imperial dial indicator, we can still convert between the different units.
01:00 Now when we're using our dial indicator particularly on an overhead cam engine, we need to get that dial indicator down so it's contacting either the retainer on top of the valve or alternatively in a bucket and shim arrangement we want to get the dial indicator to contact the edge of the bucket.
01:19 Essentially what we're trying to do here is get the dial indicator to measure something that's directly indicating the amount of valve lift.
01:27 Now when we purchase our dial indicator they're going to be supplied with a very short extension.
01:33 And for our purposes this isn't going to be a lot of use, we're not going to be able to get that dial indicator down inside the cylinder head so that it can contact the retainer or the bucket.
01:42 What we're going to need to do is fit an extension, and these are available in a variety of different lengths.
01:50 So these can be simpy screwed into our dial indicator in order to extend it to whatever length we need in order for it to contact the valve retainer or the bucket and get an accurate measure on our valve movement.
02:04 The other aspect we're going to need to keep in mind when we're fitting a dial indicator is we need a way of accurately and stably locating it so it's not going to move around.
02:14 In order to do that, we're going to use an adjustable magnetic base like this.
02:17 So this has a magnetic base that we can turn on or off to locate on our engine and also has a range of adjustable arms.
02:26 This allows us to manipulate the location of the dial indicator so that it is accurately aligned with our valve movement.
02:35 Now one of the problems we're going to find, particularly when we're dealing with a lot of late model engines that are predominantly aluminium construction is that we need something ferrous in order for our magnetic base to actually attach to so a magnet will not attach to an aluminium cylinder head or block for example.
02:54 A really easy solution to that is to simply use a piece of steel plate like this.
03:00 I've just cut this piece of steel plate, it's approximately a quarter of an inch thick and what we can then do is drill some holes into this plate to suit a locating bolt hole on our cylinder head or our engine block.
03:13 And for the purposes of fitting our dial indicator, we can simply bolt this plate to the cylinder head or the engine block and then we've got a nice safe stable platform that we can attach our magnetic base to.
03:26 In the case of our Honda B18C I'm going to attach this directly to the cam cap.
03:31 So let's go ahead and do that now.
03:34 In this instance what we're going to do is start by attaching our dial indicator to our intake cam and we're going to be fitting it to the intake valve on number one cylinder, or one of the intake valves on number one cylinder.
03:49 So we're just going to tighten our plate down here, it is important when we are using a plate like this just to ensure that it isn't going to to foul on the cam movement or any of the components in the engine as the engine goes through a full cycle.
04:03 So we'll just tighten that down again just to simply make sure that it's not going to move.
04:08 Now that we've got that located, we can take our magnetic base and we're going to locate the magnetic base on top of our plate and then we can simply turn that on, we can see that that is now nice and stable.
04:20 One of the key aspects when it comes to fitting our dial indicator is to make sure that is is aligned directly with the direction of travel on the valve.
04:30 What I mean by this is we don't want it located on the retainer or the bucket on an angle, we want it in line with the movement of the valve.
04:39 This is going to make sure that as we move the engine through its engine cycle, the dial indicator isn't going to become dislodged or fall off and it's also going to give us an accurate and true representation of the valve lift.
04:52 So in order to do this, we're going to need to start by fitting an extension to our dial indicator.
04:58 For the purposes of this demonstration, we're going to use an imperial dial indicator and I'm just going to attach a 100 millimetre long extension to the dial indicator and we can now locate that on our magnetic base.
05:39 So we want to start there, I've just lightly attached the dial indicator, nothing is tightened up there.
05:46 And what we're doing at the moment, we've got our engine located at top dead centre on the compression stroke, so both the intake and the exhaust valves are completely closed.
05:55 So what I'm going to do here is I'm going to align our dial indicator and I want to make sure that we're using a reasonable amount of travel of the dial indicator.
06:04 What we need to understand here is that at the moment, the valve is completely closed.
06:09 As we move through the cycle and the intake valve is opened by the camshaft, that retainer that the dial indicator is currently sitting on is going to move down.
06:17 So we need to make sure that when we are locating the dial indicator that it has enough travel to cover the full range of the valve movement, otherwise we're not going to be able to get a true representation of what's going on.
06:30 So we're going to make sure that we have the dial indicator relatively compressed, we've got enough movement to cover the valve lift that we're going to deal with and then I'm also going to make sure, again, that we have got the dial indicator aligned correctly with the valve.
06:47 So let's go ahead and do that now.
07:03 OK so we've got our dial indicator fitted now, I'm comfortable that the alignment with our valve is correct.
07:09 Another thing we're going to need to be careful of in some applications is that the dial indicator can actually interfere with the movement of the cam lobe.
07:19 This is going to be particularly the case on a bucket and shim type valve actuation where the cam lobe acts directly on the bucket that we're trying to also locate our dial indicator on.
07:31 So this can be a little bit fiddly because what we're trying to do is locate our dial indicator right on the edge of the bucket but we also need to be very careful that the dial indicator is not going to foul on the side of the bucket or alternatively on the side of the cam lobe.
07:47 So it's very important, once we've located the dial indicator, to rotate the engine carefully through a full engine cycle and just ensure that there is no contact between the components.
07:57 So right now we've got everything aligned and what I'm going to do is rotate the engine through and I'm going to make sure that I am seeing the full valve movement on our dial indicator.
08:24 OK so we've got full travel there, we know that we are able to measure the full travel of the valve.
08:30 This is also the ideal time to just confirm that the dial indicator isn't fouling on any of the components.
08:36 So at this point what we can also do is go ahead and zero our dial indicator.
08:40 So what we want to do is adjust our zero point so that we are seeing zero when the valve is completely closed.
08:47 We can do that simply by loosening off our stop and then we're just going to rotate our dial indicator around to the point where our needle is.
08:58 What we can do is also just make sure that we are truely zeroed by just pulling the dial indicator back and allowing it to recontact on our retainer.
09:08 So at this point I've also locked the dial indicator up.
09:11 And what we want to do is one final test and what we're looking for here is that as we move through the complete valve motion, that we do in fact come back to the same zero point, so let's go ahead and do that now.
09:31 OK so we can see that we are coming back to our zero point.
09:35 So at this point, our dial indicator is properly set up on our intake valve and we're ready to actually start taking degree readings from our intake cam.