How to Degree a Cam: Step 4: Measure and Adjust Intake Cam Timing
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Step 4: Measure and Adjust Intake Cam Timing
10.09
| 00:00 | - Now with our setup steps out of the way, we can move on and actually start measuring our valve opening and closing events, and make any adjustments required in order to get those opening and closing events to the correct point in the engine cycle. |
| 00:13 | Before we do this, obviously we need to know what the correct points are, and this information comes from our camshaft manufacturer's specification card. |
| 00:21 | In this case the Kelford cams that we have fitted to our B18C request on the inlet that the inlet valve opens to one millimetre of lift, 19 degrees before top dead centre, and that the inlet closes back down to one millimetre of lift, at 55 degrees after bottom dead centre. |
| 00:41 | Before we start making any measurements, I'm just going to mark those two points onto our Moroso degree wheel just so it's going to be very very easy for us to reference where our cam timing events are compared to where they should be. |
| 00:55 | So in order to do this, I'm just going to be using a sharpie marker. |
| 00:59 | So the first point that we're looking for is 19 degrees before top dead centre. |
| 01:04 | Now remembering in this case as well that our B18C is rotating anti clockwise, that's important to keep in mind. |
| 01:11 | So what I'm going to do is just place a little reference mark on our 19 degree point. |
| 01:17 | I'll now rotate our crankshaft around and we'll mark our intake valve closing point. |
| 01:24 | Now in this case we're looking for degrees after bottom dead centre, and remember when we're looking at our degrees after bottom dead centre, we're looking at our black marking points. |
| 01:35 | So in this case we're looking for 55 degrees after bottom dead centre, we have our 50 degree mark here, our 60 degree mark, so our 55 degree mark is right here. |
| 01:49 | Now that we've got our valve events temporarily marked on our degree wheel, we can actually go ahead and make a measurement and find out where our inlet valve is opening and closing, relative to those marks. |
| 02:00 | Starting from top dead centre, we're just going to rotate our crankshaft through until our intake valve first starts to open. |
| 02:09 | So we can take note here of where abouts we're expecting our one millimetre of lift point to be, this just gives us a reference when we are coming up on that point, now I'm just watching carefully on our dial indicator, we're just starting to life the intake valve off the seat now. |
| 02:24 | I'm just going to apply gentle pressure here on my strong arm, so I can be very very accurate with my marking. |
| 02:32 | I'm coming up on one millimetre of lift now. |
| 02:34 | So we're just going to stop there and I'm going to continue to apply a small amount of pressure to that strong arm, just to prevent the crankshaft snapping back, and we can now take note of what our degree marking is. |
| 02:46 | In this case we can see we've reached one millimetre of lift, 13 degrees before top dead centre. |
| 02:52 | We can see we've gone past our purple reference mark there. |
| 02:54 | In this case we are six degrees retarded compared to what the camshaft spec card requests. |
| 03:01 | So we know that we're opening our valve a little bit later in the engine cycle than what we're expecting. |
| 03:06 | Let's continue though and we'll compare that to our inlet valve closing point. |
| 03:21 | Again we can use the purple marker on our degree wheel there along with our dial indicator to just let us know when we are coming up on our one millimetre of lift point. |
| 03:33 | Just coming up on that now. |
| 03:36 | Again just slowly applying pressure so we can be very very accurate with our degree markings. |
| 03:42 | And we're at one millimetre of lift now so again we can just take note of the marking on our degree wheel. |
| 03:47 | In this case we can see that our inlet valve is closing back down to one millimetre of lift at 61 degrees after bottom dead centre. |
| 03:54 | Now again, this is six degrees later in the engine cycle than what the camshaft specification card requests. |
| 04:02 | So there's two pieces of information we're going to take away from this, first of all, what we're doing is comparing our inlet valve opening and closing points to the cam specification card. |
| 04:12 | In this case, in both instances, our inlet valve opening and closing points are occurring six degrees later than the cam specification card. |
| 04:20 | That's a good thing because it means that the duration that we are measuring at one millimetre of lift, also matches the cam specification card. |
| 04:29 | If we were seeing a difference in the duration between what we're measuring at one millimetre of lift and what the cam specification card gives us, this would indicate that something is wrong. |
| 04:39 | In this case, it's most likely going to involve us incorrectly setting our valve lash, in some instances though it could also indicate that there may be a problem with our cam grind. |
| 04:51 | In this case because we know that our duration at one millimetre of lift matches our cam specification card, the other piece of inforamtion that we take from this is that the camshaft is currently six degrees retarded from the ideal location, and this is what we're going to need to correct. |
| 05:06 | Before we do this though, we'll continue rotating the crankshaft around and we're going to come back up onto top dead centre before we make any adjustments. |
| 05:14 | Before we make these adjustments we do need to loosen the locking bolts around the outside of our vernier cam gear to allow us to move the cam relative to the crankshaft. |
| 05:24 | But also we do need to understand what we're going to be trying to achieve. |
| 05:28 | Now in this case, we've found we're six degrees retarded, this means that we are going to need to advance the camshaft by six crankshaft degrees in order to correct that error. |
| 05:38 | The important point to keep in the back of your mind here though is that because the camshaft rotates at half crankshaft speed, what we're trying to do is move the camshaft three degrees markings on that vernier cam gear. |
| 05:52 | That will have the effect of moving it six crankshaft degrees. |
| 05:55 | We know that our valve opening and closing events are happening too late in the engine cycle. |
| 06:02 | This means that the camshaft is currently retarded. |
| 06:04 | In order to correct that, we need to advance the camshaft or in other words have those valve opening events happen earlier relative to crankshaft motion. |
| 06:14 | In order to do this, what we need to do is take into account the direction that the crankshaft rotates. |
| 06:20 | In our Honda B18 here, because it does rotate anti clockwise, in order to advance the camshaft, we also need to rotate the camshaft anticlockwise, so that's what we're going to be doing. |
| 06:32 | We're going to be rotating the camshaft three degrees on our vernier cam gear, in an anticlockwise direction. |
| 06:40 | So let's go ahead and do that now. |
| 06:42 | Before we loosen the locking bolts on our cam wheel, we do want to just check the degree markings on our vernier cam gear and make sure nothing has shifted. |
| 06:49 | In this case our cam wheel is still on the zero mark, so we can go ahead and loosen our locking bolts. |
| 07:08 | With our locking bolts now loose, we can use a 14 mil ring spanner and we can advance the cam three degrees. |
| 07:26 | We're now going to lock up our adjusting bolts again just to prevent the camshaft wheel from moving while we go through and make our next round of measurements. |
| 07:48 | With everything now locked up, we can repeat the process we've just looked at and we can find out where our inlet valve is opening and closing, so let's go through and do that now. |
| 08:04 | OK so our inlet valve is just coming through half a millimetre of lift. |
| 08:07 | We'll keep coming through just really smoothly until we get to our one millimetre of lift point, we're coming up on that right now. |
| 08:15 | And again we can now check our degree wheel. |
| 08:18 | As we can see, we're right on our purple reference mark there, our inlet valve is now reaching one millimetre of lift, right on that point, 19 degrees before top dead centre. |
| 08:28 | So with one single adjustment there, we've got our inlet valve opening at the right point. |
| 08:33 | We are going to continue through the engine cycle though, just make sure that our closing point is still correct as well. |
| 08:47 | OK so we're just coming up on our one millimetre of lift point again. |
| 08:54 | And again we'll just hold a little bit of pressure on our strong arm there and we can check our degree marking. |
| 09:00 | Again we can see that we're right on our mark there at 55 degrees after bottom dead centre. |
| 09:06 | So with that done, we can continue back around and we can come back up on top dead centre. |
| 09:12 | So in this instance, with one single adjustment to the vernier adjustable cam gear on our inlet cam, we've got our inlet valve opening and closing points right on our manufacturer's recommendations from the camshaft spec card. |
| 09:24 | Of course it isn't always going to be quite that quick and sometimes this can be a bit of an iterative process, we may need to take two or three goes at getting this absolutely correct. |
| 09:36 | Again if we understand the relationship between the camshaft rotation and the crankshaft rotation, and we take note of the markings on the vernier adjustable cam gears, this should be a relatively quick and easy process to complete. |
| 09:49 | Once we've gone through and we've made our final adjustments and we're happy with our degreeing of our inlet cam though, it is always a good idea to just go through and repeat the process and make sure that you are getting repeatability on the readings that you're seeing. |
| 10:04 | WIth our inlet cam timing complete, we can now move on with the next step of our process. |
