Peel's head has drilled through rocker spindles to simlify the hose connections. The two outter holes that hold the head steady on can easy pierce into head oil flow too. One can check engine gauges in races during the long easy straights runing up to max heat flow / rpm/ loads when it may matter most and we see racers even turn around to check behind. I see some gauges oil filled others not, so does it matter on iso and non iso Commando powered cycles? I see everyone is missing the actual need and Norton purpose of oil gauge >According to Norton offical service instructions and plain fluid physics in Nortons', the most important, maybe only time for oil PSI guage, is to verify its not Too Much oil pressure on spring-shim setting of the pressure bypass valve and also not Too Much oil pressure on cold starts with heavy oil grade. Great to see and aim for 50 PSI and more when burning lots of fuel & rpm, but not that big a deal to see zero on the fly, so us w/o oil guages do not be made to feel like ignorant lazy damaging owners, though of course I am even with lots of guages. Of course no oil flow is deadly but Norton's mainly have over pressure issues not under pressure. Slap me silly here if I'm misleading anyone again.