QuestionI purchased a NOS Fram oil filter cannister for my '48 Ford. Lines and fittings were not included. Do you know what diameter line I should use to make the connections. I believe the in and out fittings on the filter housing are 3/8 inch. I'm not sure of the size of the fitting on the rear of the engine(input) and the return on the oil pan below the dip stick. Any idea?
Thanks for your help.
Ed
AnswerThe fittings that go into the block are probably what is called 1/4NPT (NPT stands for National Pipe Thread). The fittings on the cannister are very likely 1/8NPT. These sizes are very misleading: the 1/8 and 1/4 refer to the ID of the tubing and fittings, not the size of the wrench flats. The 1/8NPT fittings take a 7/16" open end wrench, usually. The 1/4NPT fittings take a 1/2" wrench. The NAPA store (and many other auto parts stores that supply the trade) carries all the required fittings, including adapters and tubing. 1/8 tubing is perfectly adequate for oil filter hookup.
A caution you must observe when installing this oil filter; it needs to have a restrictive orifice in the feed fitting to prevent serious loss of oil pressure to the engine. These filters are bypass type - they are supposed to be on a restricted line so that no more than about 5% of the oil passes through the filter - the theory being that if oil goes through the filter repetitively, sooner or later a particle of crud will be trapped in the filter. Monitor the oil pressure on the upstream side of the filter (before the restrictive orifice), so you can tell what effect the installation has on the oil pressure. Of course you need to put an accurate gauge on the block fitting to measure the pre-filter oil pressure to do this. You can make a restrictive fitting by using a standard 1/8NPT elbow at the filter inlet, and filling the fittings male end with solder, then drilling a tiny hole through the solder. 0.070" is usually a good size to try. Check your new filter cannister, though, it might already have a restrictive fitting in the inlet.
The same store will have an accurate hydraulic (not electric!) oil pressure gauge, and a 1/8 flex line to use to connect it to your test point through a 1/4NPT to 1/8NPT adapter. This a valuable tool to keep in your tool chest, and it's cheap!
This design is very inferior to the modern full flow filter system. Unfortunately, unless the block has been modified to place the oil filter in series with the oil pump output, there is no way to get modern type oil filtration. These bypass filters do work, and I have them on my old cars, but changing oil frequently is very important on older cars for this reason, regardless of whether or not the car has an oil filter. Most cars did not come standard with oil filters until the late 50s, and full flow type didn't appear until about 10 years later.
Your car probably should have the oil changed every 1000 miles, whether or not you install the filter.
Dick
