Anti-Drain tube back necessity

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19692000survivor
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Anti-Drain tube back necessity

Post by 19692000survivor » Sun Oct 06, 2019 9:11 pm

I have recently read several post around warnings of not having an anti-drain back tube on your Datsun Roadster engine. Do any of the vendors have these? Are they necessary if I use a Wix filter that has an anti drain back built into the oil filter itself? I have had (3) SRLs and 2 SPLs and have never seen one or if I had it I didn’t know it. I have run Wix filters on every car I own to avoid lack of lubrication on start-ups. If it’s a must for protection is there any disadvantage in running the ADB tube with a filter with one built in it? Can anyone provide a pic? Thanks Rick

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Re: Anti-Drain tube back necessity

Post by Nissanman » Sun Oct 06, 2019 10:42 pm

Unclear if you are using a CANISTER type spin on or the CARTRIDGE type oil filter?
The ADB tube is essential if using the cartridge filter: -



Image


P/N 6 is it.



Image



The spin on type should incorporate an integral anti drain back valve in the base of the filter by the screw on boss.



Image
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Re: Anti-Drain tube back necessity

Post by JT68 » Sun Oct 06, 2019 11:40 pm

Yes, you still need it. See the photo. Without the center tube, the oil will siphon/drain right out the outlet port through the main oiling system. If that happens the pump has to fill up the whole filter before you get much oil pressure.

Some folks might say it doesn't matter, and of course the bearings always have a film of oil on them anyway, but almost certainly better to have it in place. It certainly does no harm..
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Re: Anti-Drain tube back necessity

Post by 19692000survivor » Mon Oct 07, 2019 8:37 am

So from 67-70 Roadsters with a spin on filter just need to use only filters with anti drain back internal valves - right? No other protection needed - right?

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Re: Anti-Drain tube back necessity

Post by JT68 » Mon Oct 07, 2019 11:01 am

On engines we build we ALWAYS use them. Why would you not?
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Re: Anti-Drain tube back necessity

Post by 19692000survivor » Mon Oct 07, 2019 11:14 am

I am fine with it and want all the protection I can get but I don’t understand where it would go in a spin on filter. Is it internal to the filter mount block between the engine block and the filter?

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Re: Anti-Drain tube back necessity

Post by Curtis » Mon Oct 07, 2019 11:19 am

Rallye lists them. Dean doesn't seem to have them. Not sure about other vendors. You can find used ones. You want to make sure you have to push it in. If not it will get pushed out by the oil.

http://www.datsunroadster.com/PIC_PAGES ... 152-14.htm

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Re: Anti-Drain tube back necessity

Post by JT68 » Mon Oct 07, 2019 11:25 am

19692000survivor wrote:
Mon Oct 07, 2019 11:14 am
I am fine with it and want all the protection I can get but I don’t understand where it would go in a spin on filter. Is it internal to the filter mount block between the engine block and the filter?
No, It presses in to the center threaded boss that the filter threads on to.
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Re: Anti-Drain tube back necessity

Post by FergO2k » Mon Oct 07, 2019 11:38 am

Correct, pressed into center threaded boss, sticks up about 3.5 inches, (which prevents using the catalog Mobil 1 filter).
I wouldn't bet on the oil filter manufacturer taking the anti-drain back as seriously (and consistently) as they should, especially on a U-20.
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Re: Anti-Drain tube back necessity

Post by Curtis » Mon Oct 07, 2019 1:28 pm

Okay, let's make this easy. One very dirty oil filter mount with a nice clean tube from my stash. Now to finish this dash harness.

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Re: Anti-Drain tube back necessity

Post by FergO2k » Mon Oct 07, 2019 1:43 pm

That looks great, exactly what mine looks like. Off hand, that tube looks to be aluminum, which when heated up will improve the seal/press fit, which is always the goal. I "may" have mine off in the next week, and will measure how much shorter the tube is from the oil filter housing, but the scale you show looks right. Have fun with that dash harness !!!!
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Re: Anti-Drain tube back necessity

Post by Curtis » Mon Oct 07, 2019 1:55 pm

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Re: Anti-Drain tube back necessity

Post by GeoffM » Mon Oct 07, 2019 3:21 pm

So lets suppose the oil drains out of the filter when the engine is shut-down (not sure where the vacuum break is coming from but ok). That means the oil drains out of the tube as well. The oil pump runs 22L/min which is around 2.7L/sec. Whats the volume of the supposedly drained oil galleries with and without the tube?
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Re: Anti-Drain tube back necessity

Post by 19692000survivor » Mon Oct 07, 2019 4:53 pm

Thanks Curtis that picture speaks volumes.
Last edited by 19692000survivor on Mon Oct 07, 2019 6:23 pm, edited 1 time in total.

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Re: Anti-Drain tube back necessity

Post by JT68 » Mon Oct 07, 2019 6:09 pm

GeoffM wrote:
Mon Oct 07, 2019 3:21 pm
So lets suppose the oil drains out of the filter when the engine is shut-down (not sure where the vacuum break is coming from but ok). That means the oil drains out of the tube as well. The oil pump runs 22L/min which is around 2.7L/sec. Whats the volume of the supposedly drained oil galleries with and without the tube?
22/60 = .366L/s

At cranking speed it actually takes quite a while to fill up the oiling system if it has run dry-that is why it is recommended to remove the distributor and spin the pump with a drill if the engine has been sitting a while or is newly rebuilt. (Or at least remove the plugs so it spins with minimal load)

The oiling system is not a "vacuum sealed" system- air is free to enter the system at least a dozen places. Nature abhors a vacuum, so for each drop that drips from the crank galleys, running out the main and rod clearances, a drop will leave the filter if the tube is missing.

If the tube is in place AND the filter has a ADBV, the filter will only drain to the top of the tube, remaining nearly full. Having the filter upside down is even better, which is why SO many engines are that way.

Looking at it another way, gravity wants to empty the filter and oil galleys. All the bearing throws provide a path to drain it. The lighter the oil the faster that happens. I'm sure the synthetics drain quickly, they are slippery. Dino 20-50 takes a while longer.

If the car sits long enough, and then especially if it cranks for a while or doesn't start, the bearings and all pressure lubricated surfaces (cam/rockers etc) are depending on just the remaining oil film while the galleys fill back up and pressure builds- it can take much more than a few seconds.
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