Leaderboard

This is pretty much a non-topic post, but it is a head scratcher. The good news is the wandering crank sensor showed up this afternoon as well as the new extended length carbide burrs from McMaster Carr. After my rant about deliveries in another thread, McMaster, based in Illinois and shipped UPS ground, has always been outstanding for delivery. The head scratcher part is regarding the flowbench or at least the results so far. I mentioned I needed to add a sort of bellmouth to the intake port for proper flow testing. To do that I just add a small self adhesive D shaped rubber strip around the port, like used for misc. sealing projects, but I was out of it. Today I bought a small roll. All it does is provide a smooth entrance rather than the hard square edge. In any case, I installed the strip and tried the head flow again, and lo and behold it was now in the mid-180cfm range, a pickup of 8-10cfm. This seems like good news but that meant my baseline untouched results were inaccurate. With that in mind I added the D-rubber to the untouched head to hopefully reset the baseline number. On the bench, the unmolested head flows about 174 cfm, mirroring the cfm increase on the worked over head from adding the D-rubber. To verify, I stripped it off the untouched head and the flow dropped into the mid 160's, so at least that part is verified. All of the above is still somewhat predictable and I could live with that for this purpose where the numbers are helpful, but I am mostly looking for a trend without getting bogged down in the details. The reason for the head scratcher part mentioned at the outset, it seems like flow rate indications seem to be increasing on their own. After going back and forth between the two heads, it appears the head I am working on is now aver 190cfm without doing anything other than add the D-rubber?? This is very puzzling as this is a very simple design with water filled gauges to measure suction pressure and flow, no electronics involved. It could be accounted for if there is an air leak ahead of the sensing area, but nothing appears there, at least not so far. Testing for leaks is also dirt simple: cover the hole in the bench where the flow enters, crank up the suction, and if there is any indication of flow, there is a leak. I guess I should have suspected something was out of whack when I woke up the bench after a couple years being idle and I had to adjust the indicator scale for the inclined flowmeter. This has always been rock stable in the past and never varied more than one or two cfm using the machined test plates to check calibration. I know I am rambling on about this, and I want to save time by only going for the low hanging fruit regarding light porting, but I guess the GIGO adage is still true. It doesn't need to be spot on accurate for this part of the project but it must be repeatable or not worth checking. Maybe I have a mouse nest floating around inside🙃