I got so much useful information about the temp guage, I figured now I ask about the oil pressure guage for a '48 F-1. My truck has a working after market oil pressure guage that has a thin oil line that connects to the oil filter can. The factory guage doesn't work. Is the factory guage also a hydraulic style, or is it electrical? I see in the LMC catalogue an "oil pressure switch". Where on the flathead V-8 can I find this switch? Thanks

 

Ford did a fine job of hiding the oil pressure sending unit on the flathead block down behind the drivers side head, kind of down low between the head and the firewall. The original style was kind of fat-mushroom shaped, and takes a special wrench to get out anything close to easy. Aftermarket senders look more like a modern one, that you can put a socket over with a long extention. There is a white wire connecting the sender to the oil gauge so the gauge is electric in function.

Unless you order an original style from one of the restoration places, you may have trouble getting one that works right at the local auto parts place. I got one from NAPA, but it is for a SWITCH, not a gauge, so it shows over 80 pounds full time. The other type they had (which died on me fairly quickly), was for a gauge, but per the instructions it was made to make the needle ride in the middle of the gauge until the pressure dropped to an unsafe level and then it would go to zero. I want to eventually get the right one on there but for now it works.

If the gauge is bad, you may have to wait out on ebay and find a good used or NOS gauge. I replaced all 4 of my gauges with new old stock units I found on ebay.

 

Scott has your basic info. Great diagram Ross posted for the temp sender.

The stock oil pressure sender connects to it's gauge just like the single post temp sender.

 

MT, I think I got that schematic from you didn't I?? Wasn't sure or I would have said so.

There are several places selling the stock sender, which works similar to the temp gauge -- not straight resistance, a heated bimetal -- as far as I know. What I like about the stock sender system is that it takes a while to react, so you don't see it jumping around a bunch. It's well-damped in other words. Anyway, it connects at the oil filter where the tubing on your aftermarket gauge undoubtedly does. Scott's description is correct if it doesn't have a filter (or is he confused that you have a '57, not a '48? -- I always make that mistake!)

 

Ross, you didn't get that schematic from me - I just copied it to my pic file. Thanks.

Ford used several different oil pressure getups on the flatheads. I have two of the style Scott described. I took another one apart that had extra metal tubing running down the back of the filter canister that had a capillary line for a mechanical gauge (came out of a 46 truck). I'll check my 52 tomorrow and see what it has.

 

If I was anything near smart I'd fashion some tubing to get the sender up from it's little nest the way it is set up on mine. After getting a socket to fit it it's not too hard getting it out, but starting it in by hand is pretty hard with my big paws.

 

Well, fortunately for me I am awaiting a re-built motor to be delivered, so if I need to put a sensor in, I will do so before the engine is installed! Thanks again for all your help.