09-01-2020, 02:42 PM
In theory, it's pretty easy to list which of the holes are blind and can't leak and which are not and can. However, reality is that a lot of crankcases have blind holes that are no longer blind because they've been opened up by misuse over the years and the safest way is to treat all the holes the same way although those at the rear of the crankcase are often the biggest problem because they're not blind and have the largest head of oil around them.
Plan 1 is to wind a couple of turns of PTFE tape around the bolt thread. Make sure you do this in such a direction that doesn't cause it to 'unwind' when fitted. With the normal oval washers and a spring washer this often works. Using any form of silicone sealer on the thread doesn't. Plan 2 is to use the PTFE tape but replace the oval washers with Dowty seals (Bonded Washers). Plan 3 if you still have a drip is to replace the bolt with a threaded stud. Used with a Dowty Washer this should be a belt and braces option as given that with the unthreaded section in the middle of the stud, their isn't a continuous thread for the oil to run down.
I've used all options over the years and, usually, succeed in the end. My new hillclimb engine that's only had oil in it for a week has the sump fitted as Plan 1 but I note that one bolt is showing just a touch of oil to its head so will need to be re-visited in due course.
Steve
Plan 1 is to wind a couple of turns of PTFE tape around the bolt thread. Make sure you do this in such a direction that doesn't cause it to 'unwind' when fitted. With the normal oval washers and a spring washer this often works. Using any form of silicone sealer on the thread doesn't. Plan 2 is to use the PTFE tape but replace the oval washers with Dowty seals (Bonded Washers). Plan 3 if you still have a drip is to replace the bolt with a threaded stud. Used with a Dowty Washer this should be a belt and braces option as given that with the unthreaded section in the middle of the stud, their isn't a continuous thread for the oil to run down.
I've used all options over the years and, usually, succeed in the end. My new hillclimb engine that's only had oil in it for a week has the sump fitted as Plan 1 but I note that one bolt is showing just a touch of oil to its head so will need to be re-visited in due course.
Steve