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Practical Engine Building: Step 3: Engine Machining

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Step 3: Engine Machining


00:00 - Before we send our components out for the machine work to be completed, there are still a few measurements that we'd like to take while we still have the parts in the workshop.
00:10 Now in the case of our 2JZ, we're dealing with all brand new components, so the parts should be within specification but of course we don't want to make that assumption.
00:21 In some instances such as this 2JZ build, we may also want to manipulate some of these specifications in order to achieve our desired clearances.
00:32 Now I've started by finding a Toyota 2JZ workshop manual on the internet and this is giving me all of the required factory specifications.
00:42 And I'm using this to help guide me while I'm making measurements of the journal diameters on the crankshaft for example.
00:49 The workshop manual's also really valuable when it comes time to put the engine back together.
00:54 This will give us a guide as to the order of assembly as well as the torque specifications for many of the factory components.
01:04 We're going to start now by measuring the journal diameters on our 2JZ crankshaft, and just for an example we'll look at measuring the big end diameter here, big end journal diameter here on the crankshaft.
01:18 And what we want to do when we're making these measurements is we want to measure the journal in several places.
01:25 What we're doing is we're measuring in two different planes, 90 degrees opposed, and we're measuring at the front and at the rear of the journal.
01:34 Now this allows us to confirm if the journal is showing any out of round, or if there's any taper.
01:41 These are critical aspects to understand in order to ensure that our bearing clearances are optimal.
01:48 Once we've gone through and we've measured each of the big end and each of the main journals, and made sure that they are within the factory specification we know we've got a crankshaft that we should be able to work with.
01:59 Our next step here is that we're going to check and confirm our big end oil clearance.
02:06 So what we've done here is we've fitted a set of big end bearing shells, our ACL race series bearing shells into one of the Carrillo conrods, and I've also torqued the fasteners to specification.
02:20 What I'm going to do is use our bore gauge here and we're just going to zero our bore gauge in the micrometer which is being set to our big end journal diameter.
02:31 Now we can see that I'm just swinging that back past there through the zero mark.
02:36 Once we've got the bore gauge set, we can then install it into the conrod big end, and what we want to do here is measure at 90 degrees to the parting face of the big end of the conrod.
02:50 So what we're looking for here is our measurement, and we're looking at the moment, we're just coming through round about 0.05 of a millimetre.
03:01 Now this needs to be confirmed with our actual specifications.
03:07 So let's have a look now at the specifications from the workshop manual.
03:11 And we can see that the recommended clearance for a standard big end is between 0.023 and 0.041 millimetres.
03:21 So we're actually slightly larger than this at 0.05 millimetres.
03:26 However that's actually OK.
03:29 We can also see that we have a maximum oil clearance specified here at 0.07 millimetres.
03:37 So we're within that.
03:39 Now the reason that I'm happy to be slightly outside of the recommended specification is that in this instance we are going to be running a lot more power than the factory engine.
03:51 And in this situation I always like to run towards the upper end of the factory specification.
03:57 So somewhere in the region of about 0.05 millimetres is about the sort of oil clearance that I'd like to see on the big ends of a 2JZ.
04:07 So in this instance we're OK, of course we would go through and confirm the oil clearances on each of the journals.
04:14 Just because we have one that measures up OK, that doesn't necessarily mean that the other five will also be OK.
04:22 Next we can move onto the main bearings.
04:24 And in this situation we can't really go too much further because as you'll recall, we are fitting a set of billet main caps to the engine block and this requires the main bearing tunnel to be line honed before we'll be able to install the bearing shells and torque them down to measure the oil clearance.
04:44 Now this is another situation that we do need to be a little bit wary of.
04:48 Again the specification from factory for the oil clearance on the 2JZ is just a little bit tighter than what I'd like to see on a high horsepower, high RPM application.
05:01 So we're going to be monitoring this carefully after the machining process, or during the machining process we'll be consulting with our machinist there.
05:09 And our aim will be to achieve somewhere around about 0.05 to 0.06 millimetres of oil clearance on those main bearings.
05:20 Now how do we achieve this? Well there's a few options there.
05:25 In some instances we may be able to actually purchase special grades of bearing shell that allow us to manipulate the oil clearances within relatively defined clearances.
05:38 The other option if we don't have different bearing shells available to us is we can actually polish the clearance into the crankshaft.
05:47 Our options here, we can either grind or polish a crankshaft.
05:51 Grinding will not allow us to remove very very small amounts of material.
05:56 So for example if we were trying to remove 0.01, 0.02 millimetres of material, that's not a task that we can competently achieve using grinding.
06:10 However with a skilled machinist, it is possible to polish the surface of the journal, in order to remove small amounts of material and modify those clearances as required.
06:22 Now particularly with the 2JZ crankshaft, the fillets where the journals run into the cheeks of the crankshaft is what's called undercut.
06:31 This means that it actually, the radius actually drops below the surface that the bearing runs against, and this means that it's relatively easy to achieve clearance changes by polishing those journal surfaces.
06:46 If we didn't have an undercut radius in there, this does become a little bit more tricky.
06:51 We need to obviously run this past your machinist to find the best way of achieving your clearances.
06:58 OK so at this point we're comfortable with the bearing clearances that we can check.
07:04 There's one more aspect that I'm just going to cover here and this is the side clearance between the connecting rod and the crankshaft.
07:12 So if we just take one big end cap here, normally we would be doing this with the entire conrod attached to the journal, but for the purposes of demonstration, if we just place the big end cap on the journal, we can see that we can move that cap backwards and forwards.
07:31 And the side clearance is simply the clearance between the side of the conrod and the journal.
07:36 So what we can do is use a feeler blade in order to measure that.
07:41 So we'll just do that now.
07:44 Again there'll be specifications from both your conrod manufacturer as well as the OE manufacturer for what these clearances should be.
07:54 So I've just tried a 10 thousandths of an inch feeler blade in there and that's still just a little bit loose.
08:01 So we'll try the 12 thousandths feeler blade.
08:03 And yeah that's where our clearance is there.
08:06 So we're 12 thousandths of an inch or 0.305 millimetres.
08:12 So that falls within our specifications so again we know our side clearance for our conrods is OK.
08:18 It's important to check these aspects now, because if the clearance is insufficient, this will need to be addressed during the machining operation.
08:27 Next we can move on and we're going to have a look at the piston to cylinder wall or piston to bore clearance for our forged CP pistons.
08:37 So I've got one of our CP pistons here, and I've also go the specification sheet.
08:43 So the specification sheet gives us the required or specified piston to bore clearance, which in this case is listed at 0.0035 inches.
08:55 This specification is in imperial, so that's 3.5 thousandths of an inch.
09:01 Now in order to check that clearance, what we're going to have to do is first of all measure the piston skirt, and it's important to make sure that we measure the piston skirt in the correct spot.
09:13 So we'll find that on our specification sheet there will be first of all a piston size.
09:20 And that's listed at 3.3825 inches.
09:23 The important point to note as well is that that clearance needs to be measured half an inch from the base of the skirt.
09:31 The skirt is actually a barrel shape.
09:33 It's not parallel as you may think.
09:35 So we need to make that measurement half an inch from the base of the skirt.
09:40 So we'll just do that now.
09:42 Once we've made this measurement we'll be able to set our bore gauge and then we can check the clearance in the bore.
09:50 So we'll grab our micrometer and I'm just going to check that clearance at the half inch point up from the skirt.
09:59 And we can see that this particular clearance in this case does read the same as the specification from CP.
10:10 Our next step is we'll just change over our bore gauge to the appropriate size and we'll get our engine block in and we can see what our piston to bore clearance comes out at.
10:20 The important point to note here is that these CP pistons are a stock bore size.
10:26 So these are an 86 millimetre bore, they're designed for the stock bore size.
10:31 If we have excessive clearance, this isn't going to give us a lot of opportunity to do anything to remedy that when it comes to the machining process.
10:41 Once we've got our bore gauge set up and zeroed using our micrometer, we can check the actual piston to bore clearance.
10:48 So let's do that now.
10:50 So we're going to take our bore gauge and for this example we're just going to look at the piston to bore clearance in number one cylinder.
10:57 So you just want to insert our bore gauge and generally we want to make our reading a little bit down the bore.
11:03 And we also want to check the clearance at the top of the bore, the middle of the bore, and the bottom of the bore.
11:11 As well as in two different locations so we can check it at 90 degrees.
11:16 And this is just going to confirm that there is no out of round in our bores, and also confirm that our bores are parallel.
11:27 So in this particular bore we're getting a reading of around about 0.095 of a millimetre, so this is again important to understand, our bore gauge is a metric bore gauge.
11:40 And our specifications from CP are in inches.
11:44 So in order to get something meaningful, we're going to need to convert between millimetres and inches.
11:51 It's easy to do if we just remember there's 25.4 millimetres in an inch.
11:56 So just going to grab my calculator now, and I'm going to enter my reading of 0.095 millimetres and I'm going to divide that by 25.4 and it gives us 0.0037 inches.
12:10 In other words this is 3.7 thousandths of an inch.
12:14 Now this is somewhat problematic because we're already 0.2 of a thou larger than our recommendation from CP.
12:24 And this puts us in a slightly difficult position because clearly we can't machine these bores smaller.
12:31 While in itself a bore clearance of 3.7 thou is not going to be problematic, what it does leave us is in a position where we've got very limited potential to fix any discrepancies in our bore.
12:47 So in other words if we fit a torque plate and find that the bores distort slightly, we need to now trade off between ending up with excessive piston to bore clearance or it taking on board and accepting a bore that isn't perfectly round.
13:04 So this is why personally I always prefer to start with a first oversize piston unless we have a very specific reason not to, that allows us to start fresh, machine the bores, and achieve exactly the piston to bore clearance we want.
13:20 In this case the client who owns this particular motor, we're doing this project for, supplied all of the parts, and at this point we have two options.
13:30 We can move forward knowing that our piston to bore clearance is potentially going to be just slightly larger than we'd like, or alternatively we could return the pistons and swap them for a set of first oversized pistons.
13:46 Given the application and so much as we are going to be running high boost on this engine, it's quite likely that we may end up pushing the piston to bore clearance slightly larger than the recommended clearance from CP anyway, so in this case we've chosen to move forward.
14:03 At this point we've done all of the checking we can here in the workshop.
14:07 We're now going to send all of these components off to our machinist for the actual machine work to be completed.
14:15 Once the engine components were received by our machinist, this gave us the opportunity to discuss what we required or what we wanted from the machining processes, and there was also a little bit of back and forth between ourselves and the machinist as certain aspects or problems were highlighted.
14:32 And this is quite common with most machining tasks.
14:35 In particular what our engine machinist found was that the number one bore, despite this being a brand new factory block straight from Toyota, was showing a slight out of round.
14:48 Now in consultation with the engine machinist, we made the decision to increase the piston to bore clearance slightly.
14:56 What we ended up doing was increasing this out to approximately four thousandths of an inch, remembering that our specification from CP was 3.5 thou.
15:06 Now we did this because this allowed some minor amount of room to clean up in particular that number one bore, try and remove some of that slight out of round that was being measured.
15:18 But also given the high boost high power application, we felt that the additional half a thou of clearance was justified and certainly not something that was going to cause undue problems down the track.
15:32 The other aspect that we found was the Titan billet main caps that we supplied.
15:39 These were actually quite a long way undersize.
15:43 So this was a little bit more major than just align honing the main bearing tunnel.
15:49 This actually required a boring process, followed by the line honing.
15:53 Line honing can only remove relatively small amounts of material and when these caps were bolted in place we had an overlap of somewhere in the region of about two to three millimetres.
16:04 So it's quite a significant amount smaller than the factory journal size.
16:09 Another aspect worth mentioning is that the finish, the surface finish on the parting face of these billet main caps was actually quite poor as supplied and this required our machinist to dress those faces so they had the correct finish to bolt down to the engine block.
16:25 So these are just some of the considerations that often come up when we send parts out for machining.
16:32 So it's often an iterative process where we'll be discussing backwards and forwards our requirements with the engine machinist and also any problems that may come up during the machining processes will be brought to our attention so we can make decisions on how best to move forward.

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