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Practical Engine Building: Installing Conrods on Pistons

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Installing Conrods on Pistons


00:00 - One of the tasks that a lot of novice engine builders struggle with is installing the pistons onto the connecting rods.
00:06 Now when we're dealing with aftermarket performance parts it's quite common for the wrist pin to be what's referred to as fully floating, which is where the wrist pin floats in both the wrist pin bosses in the piston, as well as in the small end bush of the connecting rod.
00:22 Now with this sort of installation we need some way of retaining the wrist pin inside the piston to prevent it from falling out.
00:30 There are a few techniques but we'll start by looking at the technique of wire locks.
00:35 Now wire locks are simply a small c shaped steel clip, and these get located inside the wire lock groove inside the piston which we can see here.
00:46 We have one of these on each side of the piston.
00:48 Now when we're looking at those wire lock grooves as well, you'll also notice there's a small recess on both sides of the piston and that recess is designed to allow us to easily remove those wire locks during the piston and conrod disassembly process.
01:06 When we're going to assemble these components it's really important to make sure that the wrist pin bosses in the piston as well as the small end bush of the connecting rod are well lubricated and for this particular task I like to use a moly based engine assembly lubricant as we can see here.
01:23 The reason I use a moly based lubricant for this task is that it can take quite a while for these components to get lubrication via the oil mist in the crank case, after the initial engine start up, and this moly based lubricant provides a little bit of additional protection during this first start up period.
01:43 OK we'll have a look at the process of assembling a wrist pin here into our JE forged piston.
01:49 For this demonstration I will be assembling these components dry just so it's really clear what I'm doing.
01:57 Now in order to get the wire locks installed into the piston we want to start by installing one of the wire locks, and it's actually easiest if we use the wrist pin to help us install that first wire lock.
02:11 What I've got here is a common bulldog clip, and I've removed one of the clips from that bulldog clip and I'm going to be using that to help me.
02:21 What I'm going to do is start by installing that bulldog clip into the wire lock groove in the piston.
02:27 Just gonna slip that in like that, and once I've got that in location, I can take our wrist pin and I can gently slide that through from the other side.
02:37 And the bulldog clip will prevent it from falling out the other side.
02:41 This gives us full access to the wire lock groove so we can install our first wire lock.
02:47 Before we do that though we do want to pay special attention to where the recess in that wire lock groove is.
02:54 We want to make sure that when we install the wire locks that the ends of the wire lock don't coincide with that recess, otherwise it can make it difficult or impossible to remove that wire lock when it comes time to dissasemble the piston and conrod.
03:08 So we'll take our piston and I'm going to begin by installing our wire lock, just fitting one end into the wire lock groove.
03:17 And we want to start by fitting the end into the wire lock groove relatively high in that groove.
03:23 Now this does get a little bit tricky.
03:25 What we're going to do is use our thumbs to apply pressure to help to compress the wire lock slightly, and we should be able to get that to move into the wire lock groove.
03:37 Now in some instances we're going to be able to complete the installation of the wire lock simply with the pressure from our thumbs, however in some piston designs this becomes much more difficult.
03:48 And in this case what I'm going to do is use a small flat blade jeweller's screwdriver to help me install the wire lock.
03:55 When we are doing this it's really important that we're very careful with the screwdriver.
03:59 Obviously we don't want to scratch or mark the surface of the piston.
04:04 So what I'm going to do is just apply a little bit of pressure here with my thumb and then at the same time I'm just going to lift the wire lock slightly.
04:12 Now as I do that it does slide naturally into its groove.
04:16 I'm just going to move my thumb around so I can apply pressure just a little bit further down the piston.
04:22 We've just about got that wire lock all the way home.
04:25 Now I haven't used very much pressure with the screwdriver, haven't done anything to mark the piston.
04:31 I'll just move my thumb out of the way, and we can now install the rest of the wire lock, the final end of the wire lock, just by pressing down with that screwdriver.
04:40 So that's our first wire lock installed.
04:43 Now we can remove our bulldog clip, we don't need that anymore, and we can slide the wrist pin back out through the other side of the piston.
04:51 This would be the point where we would take our connecting rod, obviously already lubricated, and we can assemble that into our piston.
04:59 We can now turn the piston over, and we're going to install our second wire lock.
05:05 Installing the second wire lock's simply a repeat of the process we've already looked at.
05:10 We'll take our wire lock.
05:12 Again we can see our recess on the lower right hand side of the wire lock groove there.
05:16 I'm just going to locate one end into the wire lock groove, manipulate that around using my thumb, and again I'm just going to use our jeweller's screwdriver and just help to guide that wire lock into place.
05:45 And one more press and our second wire lock is installed.
05:49 It's also a really good idea to get into the habit of having a final inspection of your two wire locks once they're installed.
05:57 You want to be very sure that they are correctly located in that wire lock groove and that they've correctly located the entire way around.
06:05 So we'll just inspect both sides there and ensure that they are installed correctly.
06:10 So that completes the installation of our piston and conrod assembly.
06:14 We'll now have a look at how to remove those wire locks.
06:17 Here I'm going to be using my flat blade jeweller's screwdriver, and what we want to do is install the flat blade screwdriver into the little recess in the wire lock groove.
06:28 And what we're trying to do here is just get that screwdriver tip underneath that wire lock and help prise it out.
06:34 Now we do need to be really careful while we go about this task though because these wire locks will tend to wanna spring out of the piston and they can go just about anywhere.
06:44 So once we've got our screwdriver installed there and the wire lock is starting to move, it's a good idea to keep a thumb over the top of the wire lock to prevent it from flying away from you.
06:56 So I'm just going to install the screwdriver now, and I'm going to start by just pressing down.
07:00 As I do this it forces the wire lock inwards and starts to compress it slightly, and this begins the process of removing it.
07:09 Now I'm just going to lean back on the screwdriver a little bit and that will bring that wire lock out of the groove.
07:16 I'll just take my thumb out of the way so you can see what's happening.
07:19 And of course if I push this a little bit further, that wire lock is just going to come out of the groove, to prevent it flying away I'm just going to cover it again with my thumb.
07:29 And there, our wire lock is removed.
07:30 Now we can obviously disassemble the piston and conrod.

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