I have a 1949 F1 that I picked up about a month ago. The truck was about 98% restored with a lot of little things left to do, many of which I have completed with the help on this site. . The previous owner had replaced all of the gauges on the on the panel. The oil pressure gauge was not showing anything. I replaced the oil pressure sending unit, with a new 6 volt one and still doesn't show anything on the gauge. Is there anything else that I can look for?? Thank you in advance for any help you can give me, this has been a great site for information

 

First Thing I'd do is install a known good mechanical oil pressure gauge to confirm tne engine HAS oil pressure. The sooner the better!

 

I am going to pick up an oil pressure test kit and see just what the pressure is. If it checks out maybe I will just install a gauge instead of using the sending unit

 

Ford was still using King-Seeley senders and gauges at this time. These DO NOT WORK on an OHM/Resistance Model as many modern setups or current aftermarket suppliers have, but the are King-Seeley Distometers that work on a completely different principle.

You won't have a good time mismatching king-Seeley and ohm/resistance equipment, which could explain your reading issues. For those having issues with your stock gauges and new sending units, it's most probable that are two different "languages" being spoken. Most modern gauges and senders are simply paired ohm meters and variable resistors; the gauge measures the resistance of the sending unit circuit which changes with the gauge reading. However, our stock Ford truck sending units and gauges used a different language with King-Seeley equipment. These sending units supply a full voltage (6V, except for 56, in which 12V) through a heater wire in the gauge in the form of a square wave with the duration of the "on" being the variable determining the gauge reading. The longer the duration, the more gauge reading adjusts accordingly. It is this full voltage of current which heats the bi-metallic strip in the stock gauge that causes the gauge to read via a small gear train. Most (if not all) after market sending units are simply a variable resistor which sends a constant closed circuit of varying resistance to the gauge. Therefore, the sending units signal doesn't heat the bimetallic strip in the gauge as much making the calibration of the after-market sending units and the stock gauges nearly impossible to match up very well due to the differences in the principle of the signal.

Modern gauges are easy to pair as long as the sending units full and empty ohm readings match that of the modern gauge. Some senders and gauges are even highly adjustable in this regard, or 3rd party inline adjusters can be had.

For accurate readings, one cannot mix and match ohm/resistance based equipment with King-Seeley equipment. Your sending unit and gauge must match, either both must be stock type (King Seeley), or modern after market (with compatible ohm ranges).

 

Thank you for that info. I just did a pressure test and found at an idle there is 10 pounds pressure, when I rev up the engine I get 60 pounds of pressure. I think that I will change things over and install a pressure gauge, then I know what is going on

 

Good news, That is enough oil pressure! Is this on fully warmed engine? Was the engine rebuilt as part of the recent restoration? and lastly, what viscosity oil?

 

I have only had the truck for about a month now, The engine has been rebuilt, not sure when that was done. The person that I bought it from had the truck for about seven years, for the most part it is in very nice shape. The bill of sale and title said 67,000 miles give or take. He told me to use SAE 30w or 20-40 or 10-40. What is your recommendation on oil. I am going to be changing it as it looks pretty dirty. The truck and the engine look to be very clean. And yes the engine was warmed up when I checked the pressure

 

In my flatheads, I run Straight SAE 30 Motor Oil with a Zinc ZDDP Additive which is about as close as one can get to what Ford calls for.

Some people use 10W-40 Diesel Oil thinking that its additives are beneficial to the flatheads/older engines, but the zinc additive formulation is usually different than what is required for gasoline engines and not nearly as useful. There is uncertainty out on how these other additive packages/formulations are compatible over time. I think this diesel oil preference gets perpetuated around due to the novelty of the "life hack" or that "I know something you don't" mentality.

The traditional wisdom is that synthetic oil will have tendency to liberate deposits in the oil system. Some of these deposits may have been acting as a seal and so it has the potential to highlight weaknesses by weeping and leaking. Also, some of the liberated deposits may relocate to a inconvenient place and crate a new restriction.

Getting into the specifics of which specific oil to run will get a different answer from anyone you ask depending upon their biases and preferences.

If not using the original spec straight SAE 30 Motor Oil coupled with a ZDDP Additive, any modern multi-weight XW-30 Motor (not diesel) with a Zinc ZDDP additive will probably suffice as any oil is likely better than used up or no oil.

 

Thank you for that information

 

What oil to use is one of those questions that if you ask 10 guys, you'll get 12 differing opinions. For me, a lot of it comes from common sense. In the 40's they didn't have multi viscosity oils, or at least they were not prevalent, so that explains why it wasn't recommended. If you look at the operating manual, it will tell you to change oil every 1000 miles because oils were so crappy back then. (But of course, no one did.) They didn't have the refining and additives we have today, which is why there's always so much sludge in old, used up engines from back then. It also told you to use different weights in different temperatures, 30 weight for normal use, 40 if it was really hot, and 10 or 20 weight depending on how cold your area got in winter.

Today, if you ran a 10w30 or 15w40 from any quality oil company, you'll be perfectly fine and far exceed anything the manufacturer may have told you to use in 1949. The first number with the w (winter) is the cold weight and the last number is the hot weight. It will help with cold starts and give better protection all year round. I would not go out of my way to find or spend extra money on specialty, single-vis oils. Especially in a hobby truck that will never see work or another 100,000 in its lifetime. Assuming your engine is in good condition, and unless you're driving more than 5000 miles a year or you have a problem, change it once a year with a new filter element and you'll be good to go forever. There really is no need to overthink this.

The other common thought is that since flatheads have such low valve spring pressures compared to OHV engines, the need for a zinc additive is a non issue. You're not pushing so hard on the valves and cam that the additional friction modification isn't necessary.

And with that, as they say, YMMV.

 

Thank you for your input, very helpful