Filters without a bypass valve

[ItsManic]

This is my first post on BITOG so, HI! Like everyone else on here that claims to be an expert, I like to think I know a good bit about oil and filters and whatnot and am curious about something...
I know this may be vehicle specific so I'll be specific. I have a 1987 Nissan D21 with the 3.0l V6 and had the motor rebuilt recently. I've got just over 1500 miles on the rebuilt motor, I changed it first at 500 miles and then ran with some good 'ole GTX 10W30 dino oil that I'm fixing to change to synthetic soon. I just ran with it just to make sure the piston rings would seat properly. Guy said I could've went with synthetic off the gate and I'm a huge believer in synthetic oil, however I've seen many conflicting things about how to properly break in a motor so I said screw it and just ran with dino that I'll change after 1500 miles and switch to Supertech 5w30 full syn for my warrantied 4000 mile changes (will probably change every 3000 anyway)

What does this have to do with oil filters? OH RIGHT!

SO, the stock oil filter for this truck apparently does not have a bypass valve in it for cold starts. I'm thinking to myself, "Doesn't that make it hard to lubricate the top-end on start-up? Couldn't that bulge or tear the filter media?"
Apparently on these trucks, it relies on the oil pumps bypass built in. "Makes sense....wait, wouldn't that just dump oil back into the pan?"
After that, I started looking into other filters that would fit the truck that have a bypass valve in it like ones. I work in an oil change shop so checking to see if the gasket and filter threads match is easy.
After a bunch of digging and a final decision on the oil filter I was going to put on it, I had a question pop into my head "What if the oil pump bypass has an oil gallery that runs into the bearings and top-end anyway? That would defeat the purpose of all this"

Sooooo, that's why I'm posting here. From what I know, oil pump bypass valves will dump oil into the oil pan but, what if on this truck and other vehicles that call for a bypass-less oil filter, they thought about that and made a bypass gallery for that reason.
Might some a bit convoluted to think about all this to begin with but yet again, I suppose that's why this forum exists. I love thin oil because of pumpability and thick oil for film strength and high temp protection. I want to make sure that whatever oil I use, it's getting to everything effectively and quickly at start-up since that's where most engine wear occurs and ultimately why multi-grade oils exist to begin with.

Now with all that out of the way, I am aware of different bypass pressures and all that and already have an educated idea of what filter I will use depending on y'alls input.
On my truck in particular, if that matters, would the oil pump bypass have an additional oil gallery to bypass the filter because of the lack of one in the filter, OR, does it dump into the oil pan like my original thought and getting a filter with a bypass valve be beneficial?

 

[JimmyChainsaw]

Nissan engines from this era had the filter bypass built into the filter head.You can fit an oil filter with a built in bypass without a problem.
Nissan engines such as the SR20,RB25,VG30 and TD27 were some of the most reliable engines ever fitted to a motor vehicle.I think Nissan knew what they were doing.

 

[ItsManic]

Nissan engines from this era had the filter bypass built into the filter head.You can fit an oil filter with a built in bypass without a problem.
Nissan engines such as the SR20,RB25,VG30 and TD27 were some of the most reliable engines ever fitted to a motor vehicle.I think Nissan knew what they were doing.

Mine's a VG30i, so putting the filter with a bypass valve in it would be pointless then? ...considering it already has the bypass in the filter head.

 

[OVERKILL]

There are two mechanisms and it sounds like you might be conflating them:
1. The media bypass - This bypasses the filter media if the delta-p (pressure differential) across the media exceeds a set threshold. This is to protect the filter from excessive pressure on the media and also protect the engine in the event that the media gets blocked, the engine will still get oil. There are two types of these the first being the one that's integrated into most filters, which can be located on either end of the can, depending on the design, and the second being one that's integrated into the block or filter mount, which is common with GM applications and apparently your engine based on what Jimmy above stated.

2. The pump relief - This limits system oil pressure by bypassing oil back to the feed side of the pump once its setting is reached. Most oil pumps are positive displacement, which means that regardless of what they are pumping (and, for the sake of this discussion, ignoring some slight factors like slip and leakage) they displace the same volume of oil for every rotation. The resistance; the back-pressure experienced from cramming that oil through the gallery system is what we observe as oil pressure. Without a relief, trying to cram high volumes of heavy oil through the system could result in oil pressure hitting both unnecessary and unsafe levels, so it is capped. When the relief is hit, the relationship between pump RPM and volume forced through the system is decoupled and it will sort of plateau around that volume (though it is possible to overwhelm the relief).

That help?

 

[ItsManic]

There are two mechanisms and it sounds like you might be conflating them:
1. The media bypass - This bypasses the filter media if the delta-p (pressure differential) across the media exceeds a set threshold. This is to protect the filter from excessive pressure on the media and also protect the engine in the event that the media gets blocked, the engine will still get oil. There are two types of these the first being the one that's integrated into most filters, which can be located on either end of the can, depending on the design, and the second being one that's integrated into the block or filter mount, which is common with GM applications and apparently your engine based on what Jimmy above stated.

2. The pump relief - This limits system oil pressure by bypassing oil back to the feed side of the pump once its setting is reached. Most oil pumps are positive displacement, which means that regardless of what they are pumping (and, for the sake of this discussion, ignoring some slight factors like slip and leakage) they displace the same volume of oil for every rotation. The resistance; the back-pressure experienced from cramming that oil through the gallery system is what we observe as oil pressure. Without a relief, trying to cram high volumes of heavy oil through the system could result in oil pressure hitting both unnecessary and unsafe levels, so it is capped. When the relief is hit, the relationship between pump RPM and volume forced through the system is decoupled and it will sort of plateau around that volume (though it is possible to overwhelm the relief).

That help?

Yes, Jimmy's comment cleared up that difference for me. With my truck, only the one in the filter head and pump are present, while the filter the truck calls for does not have a bypass valve. That's why I was wondering if installing a filter that does have one would be pointless considering there is already the valve in the filter head.

 

[ZeeOSix]

Yes, no reason to install an oil filter with a bypass valve if the filter bypass valve is built-in to the engine. Use filters that are specified for that engine.

When the engine was rebuilt, did the builder check out the built-in filter bypass valve to see if it was working correctly?

 

[ItsManic]

Yes, no reason to install an oil filter with a bypass valve if the filter bypass valve is built-in to the engine. Use filters that are specified for that engine.

When the engine was rebuilt, did the builder check out the built-in filter bypass valve to see if it was working correctly?

Honestly, I do not know. I know that I got a high quality job done, everything taken apart, cleaned, hot-tanked, and the whole rotating assembly replaced. Fantastic reviews for this shop, couldn't imagine them skipping over that.