Hi guys, I've got a 58 F100, '73 302/c4 combo. At operating temp, oil pressure drops down considerably. Two questions. What is the ideal running pressure for this engine? I've tried a lower temp thermostat ( to lower operating temp) and thicker oil. I had the same problem on the stock 223. I replaced the oil pump with a stocker and nothing seemed to happen. The pressure still dropped when the oil got hot. I havn't tried synthetic oil yet but I don't believe that it would solve anything. I've heard that a high volume oil pump will just suck the pan dry. I was also told I should rebuild the heads if I try to use the HV oil pump. Would an oil cooler take care of this? That brings me to the second question, anyone have any other suggestions? I've been told that maybe the lifter bores or the lifters themselves may be worn, allowing oil to run past them consequently dropping the oil pressure. Any one want to second this notion? So, low oil pressure is bad but how low is low. I have an oil gauge with just the low/high setup. When the engine starts the needle hits just above the middle. After warmup, the needle is just above the warning spot on the gauge. I can put a suitable numbered gauge on but I would like to know what numbers I'm looking for. Well, thanks for letting me ramble, I sure like this site. John

 

Get a good mechanical oil pressure gauge. I always use the 10 psi per 1000 RPM rule.

 

My 289 idles at about 35-40 psi. You said that you tried heavier oil: what weight 40? 50? Do the cheap stuff first. How about a can of STP? I have also heard that a high volume oil pump will help. It will not suck the pan dry. Good luck, Jag

 

Step one, get a good mechanical gauge to verify that you really have a problem. If you do have a problem, my guess would be that your main bearings are beginning to go. Low oil pressure once the engine is warmed up is a classic sign of this.

On the upside, I've always been able to run them for almost an eternity this way but this was never in a vehicle that I was too worried about or that I had much invested in. Usualy an old beater car or truck.

 

What weight of oil are you using? A straight weight oil (ie. 30W) instead of 10W-30 might help also. I definitely agree with the others though; get a numbered guage; they're fairly cheap, and see what pressure you are actually running.

 

I agree with Texan especially if this is a high mileage engine. It is time for a lower end rebuild. Anything else is just a bandaid...

Vern