Oil By-pass and Biggie Filters

[tom h]

Some of us run plugged/blocked oil bypass valves in the filter adapter, to positively prevent engine shrapnel from getting spread thru the engine.

The stock oil bypass is set very low, some say it will crack open with as little as 7-8 psi.

Even if using a Biggie filter adapter and super-large Baldwin B9 filter [ http://community.webshots.com/album/36060495QXkyhh ], there is still some risk of collapsing the filter element and blocking oil flow to the entire engine

Here's a possible work-around, although I caution I haven't tried it yet.

1) note that Delco PF24, Baldwin B9, and related "biggie" filters have NO bypass in the filter. The GM design assumes there is a bypass in filter adapter.

2) The Baldwin B253 filter is same physical size as the super large B9, and in addition has a 20 psi built-in bypass! (contrasted to the 7-8 psi stock GM bypass).

3) the B253 also has an anti-drainback valve, and is even heavier guage steel than the B9. B253 is rated to 600psi typical burst. (don't know the rated differential pressure).

4) Minor Problem - the common B9 has 13/16"-16 threads, the B253 has 3/4"-16 threads (1/16" smaller).

5) Solution: re-thread the Biggie adapter from 13/16 down to 3/4".

In summary, the minor modification to use a B253 may be a good tradeoff. With warmed-up oil, I suspect all the oil would be going the the flter and none thru the 20 psi bypass. (although I don't know for certain).

The B253's built-in 20 psi bypass valve seems a reasonable compromise between not allowing shrapnel thru the engine, and avoiding filter collapse on a cold startup, or if too much RPM is accidentally engaged before warmup.

I have installed a B253 as a remote mount tranny filter, so it will be convenient to stock only 1 filter type for both engine & tranny.

 

[strikeeagle]

So you DEFEAT the bypass, to PROTECT the motor???

 

[tom h]

Originally posted by strikeeagle
So you DEFEAT the bypass, to PROTECT the motor???

It's a tradeoff -- instead of the weak 7-8 psig factory bypass, in effect replacing it with a 20 psi bypass.

The risk is, What is the liklihood of the filter collapsing AND metal shavings (from blown engine) independently and simultaneously?

It will probably be one or the other.

A motor will most likely "grenade" at higher RPM when the oil pressure is also highest (50-70 psi ?).

The key question is whether the 20 psi bypass would be completely closed or slightly open during those conditions. I don't know the answer to this, although I may call Baldwin's tech support on it.

If the 20psi bypass is closed, great. Shrapnel damage prevented. If it's even slightly open, then shavings get into the engine.

 

[azgn]

absolutely!

why would you want oil going thru the motor that doesn't go thru the filter? (what happens when the bypass opens......)

obviously, one must be careful in cooler climes.....here in AZ, there is no such thing as a "cold start"

 

[strikeeagle]

Woody,

How hot is it today???

 

[azgn]

well, it is a bit cooler, like 95...........according to the Internet.....forecast high of 106

(actually, I am at my Pinetop, AZ home in the White Mountains, 7200' and it is 69* here......)

if I kept the GN up here, I'd have to figure a way not to blow oil filters off (even in the summer)

 

[azgn]

oh, and sitting in my garage, it is rarely under 115* in the summer

 

[JDEstill]

Plus, the pressure at which the bypass is opening is not absolute pressure, it is pressure difference.

If the stock filter bypass is opening at 7-10 psi, that means 7 to 10 psi drop from the oil filter adapter through the lines to and from the oil cooler, through the oil cooler itself, and through the filter. In other words, it's probably open most of the time, especially if you have a stock size filter.

If you plug that and have a bypass just in the filter that opens at 20 psi, that means it will open only if the flow of oil through the filter alone causes a 20 psi drop. Which means either the engine is cold and the oil is thick, or the filter is plugged.

That filter bypass should alleviate filters collapsing when cold, if it flows enough.

John