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How to Degree a Cam: Step 2: Find True TDC

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Step 2: Find True TDC

05.37

00:00 - Now that we've got our cam belt fitted and our engine's correctly timed on the factory timing marks, next step is to fit a degree wheel to the nose of the crankshaft and to find true top dead centre.
00:12 Now in this case it makes it nice and easy because the front of the engine is stripped bare and we can attach our Moroso degree wheel directly to the snout of the crankshaft.
00:22 What I'm doing here in order to do that is I'm using the factory Honda crankshaft bolt and I'm using a couple of the aluminium spacers supplied with the Moroso degree wheel.
00:33 So we'll go ahead now and fit that degree wheel to the crankshaft.
00:37 Now at this point we know that our engine is on TDC so we can use this to help us adjust the degree wheel so that it's going to be easy for us to fit our pointer.
00:50 So we're going to be using this little bolt hole on the Honda cylinder head to attach our pointer to.
00:57 So I'm just going to align the TDC market approximately in line with that bolt hole.
01:02 Once we've done this we can now use our battery impact driver to tighten the crank bolt.
01:11 With our degree wheel fitted, our next step is to fit our pointer.
01:15 In this case I'm using a simple pointer that's made up from a piece of mild steel tig wire.
01:22 What we're going to do is just attach that pointer to the cylinder head and we're going to get that approximately on our TDC mark for the time being.
01:40 Once we've got our pointer fitted, we can then manipulate the pointer so that it's pointing directly at the outside diameter of our degree wheel.
01:48 This is going to make it much easier for us to really accurately read the degree markings.
01:54 Remember at this point we're only trying to get this approximately located because we still have to find true top dead centre.
02:08 With our pointer now fitted, what we're going to do is turn the crankshaft slightly away from top dead centre so we can fit our positive stop down the spark plug hole.
02:18 In this case obviously because we have our cylinder head fitted, the easiest solution for us to find top dead centre is to use a piston stop.
02:26 So let's go ahead and do that now.
02:27 Before we fit the piston stop I've just wound this out so while we're tightening the piston stop into number one cylinder, it's unlikely to be contacting the piston, I've also moved the piston back approximately 20 degrees from top dead centre.
02:44 So what I'm going to do now, it's always easiest when we're trying to find top dead centre, if we're relatively close to TDC with our stop, so we're going to come back up towards TDC a little bit and come up around about the 10 degree mark.
02:58 And then I'm just going to gently wind the positive stop down until it contacts the top of the piston.
03:13 OK so we've just made contact with the top of the piston there.
03:15 What I'm going to do is take my first degree reading.
03:19 Before I do this though I am going to move the crankshaft away from top dead centre again and bring it back up onto that stop.
03:26 It's always important when we're making our degree readings that we apply a little bit of load so that the piston is positively in contact with that stop.
03:40 OK so our first reading there we are 10 degrees away from top dead centre.
03:45 So what we'll do now is we'll turn the crankshaft back around the other way and come up again on that positive stop.
04:02 OK so in this situation we've come up on our stop again and our reading is 6.5 degrees.
04:09 In order to find true TDC we can take our two values, 10 degrees and 6.5, we can add those together on our calculator and then divide by two.
04:19 And that's going to give us a total of 8.25 so 8.25 degrees either side of TDC is where we want our pointer to be.
04:30 So now we can just make that adjustment.
04:36 OK so again just like when we're making a reading on our degree wheel, we want to make sure that when we're adjusting the pointer that the piston is positively contacting that stop.
04:45 We've adjusted the pointer now to 8.25 degrees so we're just going to rotate the engine through and come back on that stop and confirm that we have got 8.25 degrees on the other side.
05:07 Alright we've come back up on our positive stop and again we can see that we're right on 8.25 degrees so at this point we have set true TDC, we've got one more job to do though which is very important.
05:20 Before we move on, we do need to now remove that positive stop from the engine.