The Stovebolt Site Forums The Shop Area Engine Shop Oil Filter yes or no 235?

Just imported a 56 3100 with a 235, it seems to run well but it has had the oil filter disconnected and the line routed around the block to the lifters, I understand this is quite common.
I have been running Ford Flatheads in my Model A for over 10 years with no oil filter and 1500 mile changes with no issues.
I have also read the chevy 235 filter only filters about 10% of the oil.
Is it necessary to run the filter on a 235 unless it has been converted to full flow?
Anyone on here running an unfiltered 235?
Richard

They came from the factory for many years without filters so I would say you are OK. We also have better oils now.

If what Hotroddickie says about the filter only filtering 10% of the oil is true. Would it be necessary to change the filter at every oil change, since it wouldn't be getting that dirty? Just wondering.

70k miles on a daily driver only vehicle, no filter, change oil once a season = 4x/year here in central Virginia.

Only 10% of the oil gets filtered? How does it manage to do that? Is there a separate reservoir for that 10%?

If there are 4 quarts in the crankcase and one in the filter, 20% of the oil is in the filter at any one time.

If you are looking for an excuse to run without a filter you need a different one than "a Chevy 235 filter only filters about 10% of the oil".

Cletis, what Hotroddickie said is actually correct.
With a full flow filter everything that comes out of the oil pump goes through the filter before going to the bearings.
A bypass filter actually steals a little oil from the oil gallery before it gets to the bearings and after filtering, returns it to the sump. Therefor the flow through the filter is restricted by a very small return hole or fitting orifice. Out of every quart that the oil pump pumps, 90% of it misses the filter.
The theory is that the at some time between oil changes every cubic inch of oil would randomly pass through the filter.
In real life, because bypass filters were used in the days of non-detergent oils, more of the heavy debris settled to the bottom of the pan then ended up in the filter.

Not true. A disc and spring inside the filter decides what goes to the element and what goes on by unfiltered. Cut up a few and you might even form the opinion that the full flow conversion is a waste of time like I did.

The oil takes the path of least resistance, the filter would have more resistance......

I like them. You pull out the dipstick & the oil looks like it just came out of the can. It only filters part of the oil at a time but all the oil eventuly goes through it.

Curt B, Yes, because all the oil on a full flow goes from the pump to the filter there has to be pressure relief valve. When the filter becomes blocked or the oil is very cold, the bearings would starve or the screw on can could explode (seen it) due to excess pressure.
Some engines have the spring loaded valve in the block, others use filters with internal relief valves like the one you described. But at normal operating temp and a reasonable clean filter, all the oil goes through the filter.

If you can get a filter can for the engine, put it on, you have nothing to lose and maybe a little cleaner oil.
Seems to my they only recommended changing the filter every other time you changed oil.
John

The 235 had no filter, then an optional by-pass filter that, as stated, only filters a portion of the oil (the restriction is approx 1/8th inch). Funny thing is that *ALL* military trucks had by-pass filters even when they were based on some VERY civilian trucks. Some even had two (the ACKWX and the CCKW with the GM-3063 series motor).

And this was in 1940/41 when non-detergent motor was still common.

'Modern' filters are full flow, and will bypass (not filter any oil) when the flow causes a pressure differential... generally above 4000RPMS or whatever the spring design is. But generally about 50-80PSI. So in a working system, the filter will *never* block the flow of oil... a relief valve opens and bypasses the entire filter element. I'm sure there were all sorts of different filtering methods attempted over the years.... but issues with a working filter are rare.

The proper way (via the TMs I have) are to change the oil when the engine is HOT... like within 10 minutes after shutdown. The filter is changed when the element is visibly dirty. And that also included draining the filter canister... guaranteeing oil all over the engine compartment/engine.

Yepper and any filtration is better than none IMHO.

The restriction in the bypass filters is 1/16", not 1/8".

Is that for an S-2 filter or a Military Senior filter?

Thanks for the inputs guys.
I had a nasty experience about 10 years ago on a 46 Ford where a nearly new oil line to the filter split spraying half the contents of the sump around under the bonnet so i am tempted to leave the filter off. But many of the repro Ford parts are rubbish, hoping the Chevy stuff is better, certainly the parts i have ordered so far seem to be US made, most of the Ford stuff seems to be from China.
Will drop the sump to see how much crap is in there first.
I am travelling to the US in a week and will try to get to the Brothers Truck show in Anaheim hopefully pick up a sump gasket set but will see what the repro Chevy oil lines look like.
Richard

Looks like you will still have an external line routed in an unconventional manner. Are you worried about it splitting/spraying?

I use hoses on my bypass filter canister.

Some do hard pipe it.
Truck shop in orange California is a neat place to visit also.

...truck shop...

Good luck

The line from the oil pressure take-off to the head is a hard line and looks well made, if i lose this i will need flex hoses as the filter is mounted on the inner wing or at least it was till i removed it.
Rich

My comment on the use of hoses was in reference to the bypass canister only, the type mounted on the manifold.

...pic...


I was not refering to your rocker bypass line.

If you choose to use a by pass filter, they come up n eBay all the time.

I played around with a few different spin on setups for the bypass system (see here) and ulimately decided the best solution for me was to exploit the existing system using a modern high performance filter designed for bypass use. This one is 98% efficient at 2 microns.

that's what i do with my dump. on my gmc's the 228 didnt have one and it still runs fine.
this is what it looked like before i cleaned it
http://s1301.photobucket.com/user/B...amp;_suid=137165827225807111468686288676
and cleaned
http://s1301.photobucket.com/user/B...amp;_suid=137165827225807111468686288676

on the 270's that i put in the 40 and the ashton i did in this manner.
http://s1301.photobucket.com/user/B...mp;_suid=1371657430976011316549222269273
i know some that still even run the bypass filter inaddition to the full flow conversion.

just curious what is the differential pressure to cause the relief to open

The shop manual lists two numbers... 35PSI as the relief set point on the pump, but the specification page lists 45 PSI for the 235.

Most modern screw on filters will bypass at about 60psi (generally 4-5000RPMs).

I'd still run a bypass filter. To be 'proper' for the era a Frantz filter would be more correct than AMSoil

That is incorrect, most modern filters bypass around 12 pounds differential, which has absolutely nothing to do with the pressure in the system, or RPM. It is merely the difference in pressure going to the filter vs. what the pressure is going out.. Under most conditions you will never lift the bypass, MAYBE when the oil is cold and thick, and you rev it up too much, or if you have so much crud in the filter that you have more than 12 PSID across the filter. You can have a filter with a 15 PSI bypass, in a 10,000 PSI system. and still not lift the bypass.

I'm in the process of getting a 49 216 running and it had the bypass filter on it and I'm going to reuse it. I just received the two new oil lines and new canister for it. As been said, all the oil will eventually go through it...

I know this goes against what most people do but I take the oil filter off most of my customers 216's and 235's.
I always wonder what people think an oil filter is removing from the oil.
In the old days when you would pull into a service station and they would pump oil out of a 55 gallon drum into a oil dispenser that had been sitting around collecting bugs, dust, or flying grinding material etc... a case could be made that an oil filter was needed. With today's sealed containers not so much.
The other case where a filter may help is if something is failing in the engine. In this case the filter would need to be looked at closely when removed to catch such a problem(and no one closely inspects their filter, they wait until there is a noise and by then it is too late).
The particles coming off an engine from normal wear are so small that they pass right through a filter.
I know a filter sounds like a MUST HAVE idea, but so does snake oil.
I do like a filter for the break in period but that is all.
In 1990 I bought a new 4 cylinder Toyota Camry. The engine in that car sat at an angle with the oil filter on the high side. When the filter was removed, oil would run all over the side of the engine. After a few filter changes I got tired of the mess and ended up leaving a filter on it for about one hundred thousand miles. At that point I replaced it and also cut open the old filter. Not to my surprise it was spotless inside.
The position that this filter sat allowed it to drain the oil from it when sitting so I was not leaving dirty oil in the engine when changing the oil.
The car was totaled with 165,000 and it was running like a top with no oil consumption at that point.
My 2 cents.

Thanks Dave! I respect a voice of reason tempered by empircal experience. I have close to 75 k miles on a daily driver only vehicle, no oil filter these last 15 years, oil change once a season, 4 seasons here in central Virginia, USA.

Cosmo

"Under most conditions you will never lift the bypass"

The bypass in an oil filter is lifted all the time. When the engine is cold. When the filter is to dirty and when the motor at high at high RPM. Unless you have a special race filter or a system specifically designed to never bypass your pump or filter will.

An oil pump can generate many GPM of flow (exact would depend on RPM and displacement of the pump).

It is proportional to RPMs (if you can show me how a bypass can lift with the system at 0 psi let me know).

And the relief valves in the pump/block will lift at an absolute PSI.

just what exactly makes you think the filter is bypassing? What indication do you have? I have had many filters with differential pressure gauges on them, and I don't think I have ever seen one even close to bypassing.

The quality of the filter is going to decide what happens and there's some garbage ones out there so who knows when the valve opens? I completely agree with Pre68 Dave but think a manifold mounted bypass filter has an unnoticed benefit of keeping oil temperature down.

So on my 261 with full flow, and there is a way to make the 235's do the same thing, I put a spin-on adapter as low as possible on the engine and I fully expect it to keep the contaminants (metal shavings, crud, etc) out of the system. I have no real enthusiasm for the standard bypass filter as I have seen many of them completely plugged up and totally useless due to lack of proper maintenance. Good comments in this thread for sure!

the really best easy way to determine when a filter will bypass is to simply ask the manufacturer. Generally I would think they are given quite a wide margin to allow for accumulation of contaminants, and the aforementioned cold starts. But you would need to install at least a gauge before and after the filter,
the best would be an actual differential pressure gauge, to determine what exactly is going on in YOUR filter. However without actually installing said gauge(s) This is purely speculation, on all of our parts. I have taken thousands of readings on probably a hundred different pieces of equipment with differential pressure gauges, most of them run around 3-8 psid. (We would change the filters at around 8, or what ever that particular piece of equipment specified) True they were large diesel engines for maritime use, steam/gas turbines, reduction gears, hydraulic systems, things of that nature (I have never seen an automotive engine with a differential pressure gauge) and yes I will concede it does vary with pump RPM. but not to the extent that it will exceed the bypass setting. Certainly not to the degree that you could say "at 4-5000 RPM." With any sort of authority. I have also watched the differential on way too many filters climb as time went on, to NOT use a filter. They are catching something, not anything you can see, but they are clogging up nonetheless. They never really approached the bypass setting, but did rise appreciably.

Yes, at approximately 3-4k RPM most engines will have sufficient flow out of the oil pump to lift the filter bypass. I know it, I have read the manuals and the spec sheets on filters (bobistheoilguy.com is only place that is bat-crap crazy about filters and oil).

A stock SBC oil pump will move 2-5gpm dep on RPM.

Here's a graph of some modern filters and at what GPM they create the specified differential pressure:

Oil dp chart

Save ONE filter all are at or above 10psid with only 2gpm flow. This is COLD oil... but at 5W its pretty darn thin even for 32F.

Yes, I can post bypass numbers for warm oil... but I think its clear that YES, oil filters bypass all the time based on GPM, dirty media, or cold oil.

I would still run any filter (by-pass/full flow) over no filter. Just change the oil more frequently (maybe every 1000 miles) depending on conditions.

can't argue with proof like that, ONE chart with some filters for what application no one knows. Two days ago filters bypassed at 60 PSI, and 4-5000 RPM, now they bypass at 10 PSI, and 3-4000 RPM. Every 1000 miles? Water is wet.

If you really need me to post the info I can. But typically that means that even if I did, you wouldn't read it anyways.

The RPM numbers are valid for *most* motors. Again, I can post the information, or you can google it. Either way its correct.

If you were NOT using any oil filter I would definitely change it much sooner as the oil can only hold so much crud in suspension. Oh, wait... now that's wrong to... I guess you run all your cars with no filters and never change the oil? Yeah....

I could go into media flow rates, or oil pump GPM... but is that really necessary? I mean your position is simply that 'you are right' vs discussion.

If I am wrong, please correct me.

those numbers make no sense because at 10 or 12 psid, (or in the case of a factory subaru filter, 24 psid) the bypass would open and the differential would no longer increase. There are so many variables that you aren't considering. Yes it is very clear that at 34 degrees those particular filters (for what application I still don't know) would probably bypass at over 2 gpm. But what about 50 degrees, or 150 degrees? I have never heard anyone but you decree that at whatever RPM you have decided it should be today, that a filter will bypass. But apparently you read another article over the weekend. No one is arguing that the bypass may open with 34 degree oil. However at operating temperature I don't buy it. But as I said I have never seen a car engine with a differential pressure gauge, and I am pretty sure you haven't either. Basically you have produced no conclusive evidence other than you saying so. water is wet.

So i recently picked up a bypass filter fairly cheap. My thoughts are, it cant hurt, even though it may not help. But it was an option, and I have one, so I'm going to install it. My question is does anyone have a photo of a correct color scheme, decals, and how it was mounted. I've seen the installation instructions, but would like to see some more photos of paint, plumbing, and mounting. thanks!

The colors and the label were different, depending on a variety of factors: (have you looked at the Tech Tip?)

If you have a Chevrolet/GM AC filter:
- year of filter
- size of filter
- installed as an accessory or as an RPO

I've looked at the tech tip, just hoping for a more visual representation than "yellow/black". lots of gray area there. would like to Have a pic from one of our experts so I can try and match it close to right.

Unless someone has documentation for your year, use the Black & Yellow for your year?