Discussion and questions related to the course Practical Engine Building
Hey Andre and HPA -
Firstly I'd like to thank you for the content you produce, embarking on a first build is much easier when a resource like this exists, and hope I have similar success here that I did with the tuning content.
I've recently gapped my rings using a manual ring filer, being the first time using one I found my rings got better as I got to each cylinder. Naturally I had to come back and tidy up the ones that were too unfortunate at being a first attempt, I feel like I have done an acceptable job but have found getting the gaps perfectly parallel is difficult with the hand crank - this could obviously be down to a lack of experience as well, but feel like they are as parallel as I could get them without getting the gaps ridiculously big.
I measured my gaps as per Wiesco's supplied table and found I need 0.016" gap and 0.018" gap for the first and second rings respectively (the second rings were too big right out of the box so I have not touched them at all, they ranged from 0.020" to 0.021"), however due to the above I did end up having to go a tiny bit bigger to compensate for the unevenness in the first couple cylinders. Obviously I feel like being larger is always safer than being too small (no innuendo intended), but is this a safe threshold to be over by? I feel like 2 thou isn't terribly over but when we are talking about thousands of an inch obviously margin for error is a lot smaller.
Edit: Forgot to mention how big I had to go, Cyl 1-3 are feeling snug at 0.018" and cyl 4 seems to be somewhere between 0.018" 0.019" so I'm looking at a variance of about up to 2 thou for 1-3 and 3 thou for cyl 4.
While I don't really want to go back and do it again I feel like now is the time if this is going to be detrimental. Can anyone out there provide some input as to whether or not I should order another set of rings and do it again? Or is the tiny bit bigger I've gone going to be ok? I am aiming for 450KW so I feel like the extra gap might be ok anyway given the additional boost/heat/pressure/expansion but again this is my first rodeo. If you could also provide some feedback on whether or not the rings look "parellel enough" - apologies in advance if the camera angles aren't super helpful in assessing that.
Yup, from what I recall, it certainly was a tricky thing to get the hang of, but when you do...
While it is certainly best to have the ends square, as that will minimise potential leakage there, it is the minimum gap that is what counts - if it is at least the recommended value,stop filing there.
I seem to remember someone having a video on-line (Andre?) where 'excessive' gaps actually made very little difference compared to the 'right' ones. Think of it this way, 5 thou' too wide might cost 0.1% in power, but 2 thou' too tight might cost you an engine - which way would you go?
That was exactly my thought process, thinking even if I am a little bit over at least it acts as some sort of insurance. Not that I want to make an excuse for doing a potentially bad job as I've spent thousands on this motor so the last thing I want to do is cut corners.
I'm glad we're on the same wavelength, my logic now more being that at least I can er on the side of caution, while, for good practice sake I would have loved to not be up to 3 thou over, I'm not sure it's worth spending $200 for a new set of rings to correct it if it's passable (especially at right now's AUD -> USD conversion rate >.>).
Hope to hear some more thoughts from anyone with anything to say.
Thanks for your input.
Bump looking for any last bit of advice/observations before I assemble this on Saturday.
If anyone has any helpful input for consideration I'd greatly appreciate it before I slap this thing together.
Thanks in advance.
Double check you have all the parts and tools you need.
Make sure everything is CLEAN!
Take your time, checking things as you go, and if something seems a bit off, stop and check what you're doing is correct.
Don't just slap it, some engines are a bit uptight and need a few drinks before the slap and tickle ;-)