Moparman Posted October 10, 2020 Report Posted October 10, 2020 (edited) Question concerning oil pressure. Yes there are many contributing factors to this question. Oil weight, bearing wear, malfunctioning oil gauge etc. My 42 Dodge truck 218 flathead oil pressure has me puzzled. Comparing this to my 48 with a 52 230 flathead. My 48 hot running down the road holds 40psi and at a idle about 35. This is with the stock 48 oil pressure gauge. Now my 42 is a different story. Hot running down the road is about 30psi at idle maybe 15psi. stock oil pressure gauge. According to the repair manual(printed in 1947)this is acceptable. Both are running 15w40 oil. Would a bad pressure relief spring cause this or is the oil pump bad. Or am I just over thinking this problem and this is acceptable. Edited October 11, 2020 by Moparman Quote
DJ194950 Posted October 10, 2020 Report Posted October 10, 2020 Why not add a second free standing gauge somewhere you can see it in use and double check them #'s?? Just my 1st. thought, I believe I would do that even if I had to spend around $20 for a new aftermarket gauge with the cheap crap plastic lines and tap in with a fitting or 2. Seems a good investment in some piece of mind? DJ Quote
JBNeal Posted October 11, 2020 Report Posted October 11, 2020 Yep, calibration of your truck gauges can be approximated with an independent gauge to determine variance...did this with my '48 and '49 with an oil psi gauge that i scored from Western Auto before they closed down, the '49 was 5psi lower so I massaged the gauge to be closer to the others...typically a problem with your oil pressure relief spring would be that the valve gets stuck, allowing oil pressure to drop to about 5psi at 40mph...if the pump was bad, you could either have varying pressure readings or a null reading... Quote
1949 Wraith Posted October 11, 2020 Report Posted October 11, 2020 My '42 Canadian factory workshop manual for my 1942 Fargo with 218 lists 40 psi highway and 15 psi at idle. This is what I generally run in my '42 with 10W30 oil, but my 1951 218 runs a bit higher at around 45 and 30. You state that you have a 201? I think the '42 Dodge original was a 218 T112. Quote
dcotant Posted October 13, 2020 Report Posted October 13, 2020 I just changed oil gauge and gained 5 psi so it is likely the gauge imho. Quote
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