The Stovebolt Site Forums The Shop Area Engine Shop Oil filter housing question, '56 235

Gotta question, folks- Is it advisable (or advisable not to) pull the oil filter in this engine without draining the oil from the engine? I know this is sounds like a stupid question, but I had my timing gears replaced last fall, and I sent a case of oil to replace the oil lost when they pulled the pan to get to those tricky bolts on the inside of the timing cover. I didn't send the filter, since it was a timing job, not an oil change. Anyway, after adjusting my valves Sunday, I started thinking about that old filter. It's been over a year since it's been changed. The truck sat for 9 months before I finally changed the timing gears. And the gears were changed this summer. I've been driving my '04 Silverado 3500 since the gears went out. After working out some bugs in the last few weeks, the bomb is ready to be my daily driver again, so I figured since the filter is on top and I can change it without losing oil that has less than 100 miles, I'll just go ahead and put in the new filter.

But after loosening the filter cap bolt this morning, something strange happened. The bolt came loose, but wouldn't come all the way out. It's loose enough to wobble it around (out of plumb), but since it wasn't just sliding out as usual, I don't want to screw something up by forcing it. I also tried to pop the cap off, but it seems like there's a vacuum in the filter housing. Since this is the first time I've ever attempted to pull the filter without draining the oil before, I'm now wondering if this is something you just 'don't do!'? Can somebody tell me if they've ever pulled a filter while the system is unopened? I know when I pulled the filter all the other times, the housing was still full of oil, so I'm aware that it doesn't drain down. But now I'm wondering if the system builds up an air tight vacuum when unopened. What I'm really wanting to find out is if I'll get drenched in an oil bath if I go ahead and pull it off this way, or is the cap just tight, and I can just go ahead and do the job and change the filter. Thanks for any ideas on this. Lee

The filter can be changed without draining the oil. The oil filter canister is pressurized when the engine is running and drains to the crankcase. When you shut the engine off the filter will depressurize but not drain fully because it drains back from the center pipe and the drain, a 1/16” hole is about 3/4 up from the bottom. It should not be under a vacuum. The lid is more than likely stuck to the gasket. Tap it and it should come off.

The oil canister and filter cartridge was an option in 1956.
It's not uncommon to find an engine without a filter.

The bolt in the cover is captive. It's designed to stay with the cover.
If the cover does not want to come off, then rust, sticking gasket or sludge is holding it down.
When you get it apart, make sure the parts inside are in the correct place and are oriented properly (see picture).

Thanks, guys. I sort of figured it must be a sticky gasket, but I didn't want to take a chance and get soaked. Since I've never opened it up except when I change the oil (abut 8 times now), it would just be my luck that it would do something I wouldn't expect. It's been this long since it's been changed, I felt it could wait one more day till I found out for sure. Thank you again!