Just recently got a 38 Ford with an 85 flat head in it. Noticed today as I was driving it. That all the sudden the oil pressure went away. Yet while testing it after I installed new carb on the driveway pressure was fine. Didn't get hot or noisy has plenty of 30W oil in the pan. Do you think it could be the sending unit getting hot, or maybe the original gauge? I'd really rather not blow up my engine before I figure this out. Already blew up one engine this week -- lawn tractor.
If it is not handy, borrow one. Spidercoupe is right. Could save you a whole lot of unnecessary work. Don't ask me how I know...
OK, it's been an hour or so now. So I went out and started it up, WALA, it's got oil pressure again. I will put a manual gauge on it just for giggles before I go any further. Might be a good idea just to install mini gauges under the dash, rather than trusting the originals.
Installed the manual gauge. Shows about 25# when first started up. As the engine warms up the oil pressure goes down, not quite to zero at idle. Running down the road at 50 mph with a temp of 195 it shows 10/12#. There is no signs of smoke from the exhaust, so the rings appear to be OK. No noise from the valves either. I have not run a compression check on it. But I have no idea how many miles the engine has on it. I know one of these days it will need a complete OH. Would a new oil pump right now maybe solve this problem for a while? How about Valvoline 50W racing oil, a can of STP? Just a thought. Been a lot of years since I worked on a Flathead and I don't remember as much as I should.
At this time of year? In Texas? Heavier oil would be a good place to start. 50W won't hurt it any, 20W 50 would do well too.
A good rule of thumb for oil pressure is 10# for every 1000 rpm, some of the older style engines have ran for years with less ideal oil pressure conditions...this is just a guideline
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