VCCA Home Forums TECHNICAL - GENERAL Mechanical - Engine, Trans, etc Question about an AC oil filter on a 216

Hi all
I have a question regarding the fittings used on an AC bypass style oil filter on an original 216 engine in my 1946 ¾ ton Chev truck.
Regarding the tee fitting screwed into the main oil gallery towards the rear of the engine… does this fitting have a smaller orifice built into it to restrict or meter the flow of oil going through the filter?
If it does… does anyone here know the exact size of the orifice for sure?

I ask because this engine currently has an after market filter a previous owner installed on it… and it looks like they used an off the shelf wide open brass tee at this location and I think it may be allowing way too much oil to flow to the filter from the pressurized oil gallery.

I’m going to remove the after market job presently on it and put an AC S-646 on the front runner of the intake manifold. I may be wrong, but I think the proper filter would be an AC S-2 mounted on the firewall, but I like the convenience of the location of the S-646, and the P115 or C115 element which I stock for other trucks anyway. Plus, it’s much easier to find a good S-646 than it is to find an S-2. So I think I can live with the lack of authenticity, but I need to get the flow rate right.

Thanks for any information anyone can give me on this

If you don't get an exact size, I've messed with a lot of bypass filters (funny enough Toilet Paper filters) and have them on our modern cars.

Bypass filters work best with the lowest possible flow rate. I've threaded plugs/bungs into fittings and then drilled with Index drill bits about the width of a hair and this provides enough flow for filtering. Basically the smallest drill bit you can find. You can always go bigger later if the filter takes a long time to heat up. There is no downside to restricting the flow too much.

I won't even bother adding one on my 216 as I don't like the engine failure point and the pressure is already low. It's just way too easy to just change the oil way before it's truly dirty so filtering isn't really necessary for my intended driving.

Thanks canadiantim. I'd still like to know the actual size hole AC used. But do you happen to know the size you settled on?
This truck will likely still see some pretty dust roads, and the breather system isn't filtered, so I'd like to keep a filter on it between oil changes no matter how short they are. :-)

Toilet paper filters (or cotton waste like C115's) were actually good filters weren't they! If they were used in low flow bypass situations. They filtered much smaller particles out than a full flow filter will, and when used beside a full flow system gave the best protection possible. If I remember right, some filters on big heavy duty applications used to combine both into one filter.

Ah yes, the breather system. I have a pad the goes inside the rocker cover that is suppose to quiet the valvetrain. I want the dirt snagging capability as it sits just inside the valve cover breather slots. These breather slots bother me too...

I used approx a #65 (.035") bit. It was so small I had to wrap it with sandpaper to hold it in a drill chuck. See here:

https://www.micromark.com/20-piece-...77afB6AIVB7vsCh0BAwgREAQYAiABEgIES_D_BwE

Thanks for that!

The original Ac fittings had no restrictions. There should be enough restriction passing through the fittings, lines, filter element and center return hole,etc.

In my many yeas of experiance with this set-up I never detected any difference in the oil pressure in an engine with or without an oil fiter. The filter oil feed is taken directly from the main oil gallery which feeds the main bearings only which is the only location that get full oil pressure.

To eleminate dust being drawn in through the rocker arm cover vents a 1949-1953 rocker arm cover with the top oil filler cap could be used, The cover vents in that cover could be closed off and a 1955 and up mesh breather/oil filller cap could be used.

Thanks Gene

I have to admit that the lack of a restrictor surprises me. But that's nothing new, I've been surprised many times before.

My uncle used to stuff felt into the slots in the rocker arm covers on his 1941 and 1946 trucks. He said he hammered the rear slot closed and sealed it because rain water would somehow get through the hood hinge, pool on the back of the cover and run straight into the engine. I assume he changed the felts when he changed the oil but really don't know.

Thanks again.

Of course a later cover as you suggested would be the best solution!

Years ago there were many unpaaved roads that created a lot of dust. With todays amost dust free roads I believe the dust intake is almost none and colllector cars are driven so little compared to modern every day cars I just do not worry about dust intake. I am concerned more about gas and water and acids in the oil.

You are right again Gene.
Dust isn't quite the issue it used to be. But up here on the Canadian prairies we still do have a lot of gravel and dirt roads. Even in the city it gets quite dusty after the snow all melts and before we get a good rain to wash things down. And the wind usually blows here. :-)

You stated that the oil pressure shouldn't be affected by the amount the filter takes. If the main bearings are loose enough to make just a little noticeable noise, how much would that lower my pressure?

Here's whats happening...
When I got the truck it had some god awful heavy oil in it. It ran about 14 lbs on a non original gauge under the dash with hot oil at about 2000 revs as it should.
I drained it and put in 0w-20 as a flush.
Starting cold it shows 25 lbs. After 5 or 10 minutes and the oil is hot it's down to about 9 lbs and idles with about 4-5 lbs. At this point the filter is surprisingly hot to touch suggesting a fair bit of flow there. And I can hear a faint noise now that sounds like piston slap but not sure.
I checked the viscosity stats on the oil and it maintains the same viscosity as any straight SAE 20 at 210 degrees so that shouldn't be a problem. And we still run another 1946 on the farm that worked just fine on 20w-20 diesel oil when we could get it.

I'll be dropping the pan now anyway to check for sludge blocking the screen. I would have expected plugged lines to the rods to raise the pressure, so don't think that is the issue.
The rate that the filter got hot at made me wonder how much oil was being bled off the pressure side of the system.
Thanks again.

The filter shouldot decrease oil pressure any mount. My 1950 with a filter has perfectly normal pressure.
The rods are lubricated under low pressure through the oil distributor valve. I would highly recommend droping the pan, cleaning the screen and making sure all rod oiling tubes are open.
It would be easy enough to remove the oil fiter from the circuit with a pipe plug and see if it makes a difference.

Yep on the darn dust! and on the 0W20. I use 0W20 in everything year round (even for towing) except snowblower and lawnmower that get 0W30. I've done oil analysis on our vehicles and never any wear particles. You could go thicker like a 0w30,5W30,10W30 with a worn engine as they are all 30 when hot. This would help reduce leaks more than anything and maybe help oil pressure slightly.

It would be a good idea to drop the pan, adjust the rod shims and clean out any sludge.

"Yep on the darn dust! and on the 0W20. I use 0W20 in everything year round (even for towing) except snowblower and lawnmower that get 0W30."
Nice to hear from someone else who isn't afraid of lighter oils!
And the value of fast startup lube.
I too confirmed with oil analysis.
I have a 76 Chev 1/2 ton with a 350 on the farm that has ran nearly all of it's 150,000 miles on straight 10w oil year round. And it's one of the few small blocks from that era I know of that never ground the camshaft out of itself. Never had a cover off yet.

Too damn cold to lay under the 46 and pull shims, but I will be at some point!

In my early days servicing trucks 1 brand (forget which) had a secondary partial flow centrifical filter as a standard fitting. In the regular oil change interval I would scrape upto a 1/4' of "dirt" off the inside of these units, and that was after a full flow paper element filter as well.
Tony