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How to Degree a Cam: Step 5: Measure and Adjust Intake Cam Timing

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Step 5: Measure and Adjust Intake Cam Timing

05.12

00:00 - At this point we're going to simply repeat the process that we've looked at in the last step, only this time we're going to be degreeing the intake cam.
00:08 I've already gone ahead and swapped our dial indicator across from the exhaust valve onto the intake valve.
00:15 We've made sure that it's located correctly on the retainer, that it's clearing the cam lobe during the full rotation of the engine, and I've gone ahead and also zeroed that as well, making sure that it comes back to zero each time the valve closes.
00:30 On our intake cam, according to our cam spec card, we're looking for the intake valve to open at 15 degrees before top dead centre and it should close back down to 1 millimetre of lift 51 degrees after bottom dead centre.
00:46 So with that in mind, let's go through and we'll make an initial measurement and see what our cam timing is.
01:08 Alright we've got our 1 millimetre valve opening point there and we can see that we're sitting at 18 degrees before top dead centre.
01:15 Remembering that our spec card suggested 15 degrees.
01:19 So at the moment our valve opening point is 3 degrees advanced.
01:22 We'll make a match mark there on our degree wheel and we can check our closing point.
01:40 OK we've got our intake valve at 1 millimetre off the valve seat while it's closing and we can see that our degree wheel's showing that we are 48 degrees after bottom dead centre.
01:51 So remembering that our cam spec card suggested 51 degrees.
01:55 We know that we are 3 degrees advanced on closing there.
01:59 So we'll make a match mark here and we'll discuss our results and what we need to do.
02:09 So first of all we know that both our valve opening points and our valve closing points are both advanced by the same amount, by three degrees.
02:17 So this gives us our sanity check.
02:19 We know that essentially the valve duration at 1 millimetre lift that we're measuring here on the engine is exactly the same as the cam manufacturer's spec card.
02:30 What this means though of course is that our cam is overall advanced by 3 degrees.
02:34 So to correct this, we're going to need to retard it by 3 degrees, remembering again that the marks on our vernier adjustable cam gear, each mark represents 2 degrees of crankshaft movement.
02:46 So what we're going to be doing is moving the cam by 1.5 of those marks.
02:52 We'll go through now, we'll loosen the vernier adjustable cam gear, the bolts on it, and we'll make the adjustment.
03:19 Alright with our first round of adjustments made there to our intake cam, let's go ahead and see if that's fixed our discrepancy.
03:42 We've just come up on our 1 millimetre opening point and we can see this time we are almost exactly on our specification of 15 degrees before top dead centre.
03:53 So we'll remark that and we'll check our closing point.
04:12 And looking at our closing point we can see that this is also on our specification now at 51 degrees after bottom dead centre.
04:20 So we'll make a mark there and we'll discuss what we've found.
04:31 So there with just one adjustment to our intake cam, we've essentially got right on top of our specification, our opening and our closing points exactly match our cam specification card.
04:42 So at this point our work is done.
04:44 I will point out however that with this style of adjustable cam gear particularly, it is very difficult to make accurate and small adjustments to your cam timing.
04:54 Normally this becomes an iterative process that may take 3 or 4 goes before you get exactly where you need to be.