While our S54 rod bearing widening solution is a great way to save engines that have already spun a bearing, we believe the S54 engine will run a long time on stock bearings if the proper maintenance is performed. Oil changes at low intervals along with replacing rod bearings pre-preemptively will lead to a long living engine. If you have concerns about the health of your S54 rod bearings we highly recommend doing Blackstone Oil Analysis at each oil change. Bearing wear will be shown by high lead and copper on your oil reports.
On the S54 we have seen several components fail that lead to engine rebuilds, the most devastating has proven to be the rod bearing. To prevent this we recommend changing out rod bearings every 75k to 125k miles or every season for race cars. Doing this job requires suspending the engine from the top, dropping the subframe, and removing the oil pan and oil pump. For this reason we encourage our customers to wait until they have to do an oil change so it can be done at the same time and save on oil costs.
S54 engines manufactured prior to 2003 come with larger rod bolt that are not supposed to be replaced according to BMW TIS. The later engines use a rod bolt that is smaller (torx head) and is one time use. On the early engines we prefer to use ARP fasteners because we don’t know the condition of the stock rod bolt. On the newer 2003+ engines we have found that the stock bolt is completely reliable and a bit cheaper than the ARP bolts so we will typically use those unless the customer requests ARP bolts. In our bench testing we found that the ARP bolt in the 2003 and newer engine needs to be stretched beyond the ARP specification to achieve the same bore shape as the stock BMW bolt.
A benefit of the ARP bolt design is that it allows us to use the rod stretch gauge to preload the fasteners. Because the rod bolt is arguably the most critical bolt in the engine, we like being able to use the most accurate method we can for tightening it. By using rod bolt stretch we have found that depending on conditions the torque can vary as much as 10ft lbs from fastener to fastener to achieve the same stretch. Using ARP hardware take slightly more time using the stretch method but we believe the peace of mind and longevity is worth it on the earlier engines. Another benefit of the ARP bolts is that they can be reused in the future instead of replacing them in the future. This is particularly useful on a track or race car that will be serviced frequently.
We do of course understand that certain customers are on tight budgets so when requested we will use stock bolts on both the early and late engines. We have never seen a failure on a stock S54 engine that could be directly tied to a failed stock rod bolt so we are confident that the OEM solution is sufficient. We’ve also been successfully using WPC treated BMW Genuine S54 rod bearings for the last several years. WPC has published some test results that indicate that WPC bearing treatment increase bearing life and bearing load capacity. The cost of WPC treatment is small compared to the overall cost of BMW Genuine rod bearings. Because of the small cost increase we always encourage our customers to opt for this upgrade when performing this job.
For an estimate on having your rod bearings replaced at our facility in Irvine please give us a call or contact us via e-mail.