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Practical Engine Building: Step 3: Engine Machining

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Step 3: Engine Machining

09.00

00:00 - At this point we're ready to send all of our engine components out to our machine shop for engine machining.
00:06 Before we do this though there are still a couple of checks that we can do, just to make sure that the components we've got are going to give us the sort of clearances that we need.
00:16 Now in this case because we are starting with a first oversize set of pistons, there's no potential for us to check our piston to cylinder wall clearance.
00:24 This is going to be set by our engine machinist when the cylinder block is bored and then honed.
00:30 Likewise for our main bearings, I'm not going to go through the process of checking the clearance here because we are fitting our aftermarket Mazworx main stud kit, we're pretty confident that this is going to result in some distortion in that main bearing tunnel, just from experience with these sort of stud kits on other SR20s, and this is going to require our engine machinist to line hone the engine block.
00:56 So at this point there is no benefit in us checking the clearances on our main bearings.
01:01 What we can do however is measure our crankshaft and make sure that all of the journal sizes are on specification, and we're also going to go through the process of checking our big end oil clearance using one of our K1 Technology connecting rods.
01:16 At this point it's also worth mentioning that depending on exactly what you're doing with an SR20 rebuild, you may choose to use the factory Nissan graded bearing shells.
01:26 And this allows you to essentially mix and match different coloured or graded bearing shells in order to achieve specific clearance on both the mains and the big ends.
01:36 This does require you to take note of the numbers stamped into the front of the crankshaft, there'll also be corresponding numbers on the engine block, and then also corresponding numbers on the connecting rods.
01:48 And this will help you to go through the Nissan workshop manual and decide on what colour or grade bearing should go on each of the journals.
01:57 Even if you are going to be using the factory Nissan bearing shells, it does still pay to measure your crankshaft journals to just make sure that on a high mileage crankshaft, there isn't some wear showing, and the journal size isn't actually corresponding to what's been stamped on the front of the crankshaft.
02:15 Alright we'll start my measuring the main journal diameters on our crankshaft, and we know from our SR20 workshop manual that this journal diameter should be 2.1636 through to 2.1646 inches.
02:28 So we're going to take our micrometer and we'll start by measuring our front main bearing journal and we've already gone ahead and cleaned that journal down so we're ready to take a measurement.
02:39 Now we'll take one measurement here however it is important to note that when we are measuring our journal diameters on our crankshaft, we will be taking multiple readings.
02:47 What we want to do is take a reading at each edge of our journal and we also want to take measurements in two planes.
02:55 One perpendicular to the other and this allows us to see if there's any taper showing on the journal and it also allows us to see if there is any out of round on that particular journal.
03:06 Again, our workshop manual will give us limits for both of those aspects.
03:10 So with our measurement complete on our front main journal, we can see that our measurement is 2.1642 inches.
03:19 So this falls nicely within our range and this would make our front journal a grade one journal if we were to be using the Nissan graded bearing shells.
03:27 Of course from there would repeat this process on the remaining four journals to make sure that they are all within the specification.
03:35 Next we can repeat that process, only we're going to now measure our big end journals on our crankshaft.
03:41 Again from our workshop manual, we know that the size of our big end journals should be between 1.8880 of an inch and 1.8887 of an inch.
03:52 We'll take our micrometer, again we're going to measure our front or number one big end journal.
04:00 Again when we're going this we would do exactly the same process, we're going to take multiple readings so that we can check for any taper in our journal, as well as checking for out of round.
04:10 Checking our measurement there we can see that it measures at 1.8884 inches, which is pretty much right in the middle of our specification range there.
04:20 Checking with our workshop manual we can also see that this makes our number one big end journal in our crankshaft a grade one also.
04:28 From here we'd continue that process and we'd measure the rest of our big end journals on our crankshaft.
04:34 So at this point we should know that all of our journals are within our workshop manual's specification range.
04:40 The next step we're going to go through is checking our big end clearance or big end oil clearance using one of our K1 Technologies connecting rods.
04:48 So I've already gone through here and I've assembled a pair of bearings shells into this connecting rod and we've torqued the rod bolts up to specification.
04:57 What we've done here is we've taken our measurement using our micrometer on our number one big end journal and we can now use this to zero our dial bore gauge.
05:08 So let's go ahead and do that now.
05:11 What we're going to do here is we're going to take our dial bore gauge and we'll locate that between the two anvils in our micrometer and we're just going to swing that back and forth and we're just going to zero our dial indicator.
05:24 And we can see that at this stage, I've already gone ahead and zeroed our dial indicator and we're rocking that backwards and forwards through our zero point now, so we're ready to take a measurement.
05:35 What we're going to do is take our connecting rod and we're going to gently insert the dial bore gauge into the connecting rod journal and what we want to do is take our measurement perpendicular to the parting face between the rod cap and the body of the connecting rod.
05:52 So let's go ahead and do that now.
06:00 So as I rock the dial bore gauge through the journal here we can see that we're coming to rest at about 0.05 millimetres.
06:08 And it is important to just mention here that this particular dial bore gauge is a metric bore gauge so it's important if we are working in imperial units we need to convert between metric and imperial.
06:20 In this case 0.05 or 500ths of a millimetre, is the equivalent of just on 2000ths of an inch.
06:27 Now that actually happens to be exactly what we're shooting for here with our big end oil clearances.
06:33 We're just towards the upper region, upper range, of the factory Nissan specification, we know that that's gonna be suitable for our particular power aims.
06:40 It is gonna be important here just to recheck this though after the crankshaft has been to our machine shop.
06:48 We already know there is some very light marks and scoring on our journals, nothing too significant but this crankshaft, as would be typical in any engine building job where we're reusing a factory crank, is going to end up having those journals polished, so we'll want to recheck and just make sure that the polishing hasn't affected our oil clearance.
07:08 We're going to move on now and make one last check and here we're going to be checking our big end side clearance for our connecting rods.
07:16 And what we've got here is one of the caps from a connecting rod, and we're looking here at our side clearance which is essentially just the clearance backwards and forwards if we move the cap on the journal.
07:28 We wanna make sure that we have sufficient clearance there.
07:30 if we don't, this is going to need to be corrected during the machining process.
07:34 So we want to be very careful here and make sure we don't overlook this.
07:38 What I'm going to do here is take a set of feeler blades, and generally we want to see our side clearance be somewhere in the region of about 10 to 14 thousandths of an inch so let's just get started here, and we'll select a 10 thou feeler blade.
07:54 We're going to place our big end cap on our journal and I'm just going to gently insert that feeler blade between the side of the cap and the crankshaft journal.
08:04 And in this case our 10 thou feeler blade is very loose in that journal so we know that our clearance is already greater than 10 thou.
08:11 We'll step up here to 14 thou and see where we're at.
08:15 Again we'll just place that cap back on the journal and this time we can see that our 14 thou feeler blade is actually a little bit tight in there.
08:24 So our clearance at the moment is somewhere between 10 and 14 thou.
08:28 This isn't a clearance that is too critical, we just need to make sure that our clearance isn't too tight and isn't too excessive.
08:36 At this point we're quite happy with what we've got there.
08:38 Again of course we'd go through and check the rest of our clearances there for both our big end oil clearances as well as our side clearances on our connecting rod.