Engine Building Fundamentals: Filing Piston Ring End Gaps
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Filing Piston Ring End Gaps
03.43
| 00:00 | - Now that you've decided on the ring end gaps you want to run it's time to check and set these end gaps. |
| 00:06 | The first step is to unpack your ring set and distribute the rings to each cylinder. |
| 00:12 | When we're gapping the rings, we'll be doing so to suit each individual cylinder. |
| 00:17 | This allows us to account for any minute variations in the finished bore size and ensures each ring end gap is perfect. |
| 00:26 | When you unpack the rings, it's important to make a note of which ring is which. |
| 00:31 | Usually, this is quite self-explanatory as the rings will be different thicknesses and hence will only fit into their respective ring groups. |
| 00:40 | The ring manufacturer will also often package them separately and note on the packaging which is the top ring and the second ring, for example. |
| 00:49 | Now, we need to fit the rings into the cylinders so that we can measure the end gaps as delivered. |
| 00:56 | If you've used a torque plate to bore and hone the block, you're also going to want to check the ring end gaps with a torque plate installed. |
| 01:05 | Installing the rings into the cylinder is best done by hand by slightly compressing the ring and gently pushing it down into the cylinder. |
| 01:14 | We want to make our end gap measurement with the rings located a little way down the bore to give us an accurate measurement. |
| 01:22 | And it's also critical to ensure the ring is sitting square in the bore before measuring the gap. |
| 01:28 | There are special tools for locating the ring in the bore. |
| 01:32 | However, if you don't have one of these tools I find the easiest solution is to use one of the pistons with one of the oil control rings temporarily installed on it. |
| 01:43 | You can then press the piston into the cylinder upside down until the oil control ring contacts the deck surface of the block. |
| 01:52 | This will locate the ring around about 20 millimetres down the bore and ensure that it's square, ready to be measured. |
| 01:59 | Before measuring the end gap, it's a good idea to inspect the gap and see if the ends of the gap are parallel. |
| 02:06 | It's common to find that the ends won't initially be parallel and we'll need to do some work to correct this while filing the ring end gap. |
| 02:15 | Now we can use a set of feeler blades to check the end gap. |
| 02:19 | We want to select a feeler blade that offers just a little resistance as it's pushed through the ring end gap. |
| 02:27 | Now we have a starting point for the ring end gap. |
| 02:30 | And we know that if the end gap is parallel so we can begin filing the ring. |
| 02:34 | When filing the ring, we only want to file one end of the ring, not both. |
| 02:39 | When selecting the end to file, you'll typically find that one end is relatively square and the other may be slightly irregular in shape from the manufacturing process. |
| 02:51 | The aim is always to achieve a square and parallel end gap so we would choose to file the end that is irregular. |
| 02:59 | When filing the rings, it's important to always file the ring from the outside towards the inside to avoid potentially damaging or chipping the inlay coating on the ring face. |
| 03:12 | It's also easy to file the ring too far. |
| 03:14 | So the key is to make small adjustments and check your progress frequently. |
| 03:20 | Once the end gap has reached your desired measurement you can then deburr the ring end with a fine file. |
| 03:27 | You can now go through and repeat the process for the remaining rings. |
| 03:31 | This can be a slow and laborious job but it's one of the most critical parts of assembling the engine. |
| 03:37 | And it needs to be treated with care. |
