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Technical Flathead oil filters

Discussion in 'Traditional Hot Rods' started by Pete F, Feb 21, 2017.

  1. Pete F
    Joined: Feb 12, 2017
    Posts: 40

    Pete F

    So is it me or do a lot of you guys not run oil filters on your engines.
    I forgot to drill the block for the 95% oil filter setup and was thinking of running the partial filter but a lot of pictures don't have any filter so I was wondering what's the consensus is.

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  2. tubman
    Joined: May 16, 2007
    Posts: 4,863


    In my opinion, if you have a stock (or near stock) engine that is in good shape, a stock bypass filter is all you need on one of these engines. Given the conditions under which these engines are operated these days (no dirt roads, oil changes every year after minimal mileage , and optimal storage), the ability of a bypass filter to remove smaller particles than a full flow (or close) conversion trumps any extra filtration the other systems can provide.

    If you are going off-roading or operating under other extreme conditions, maybe one of the other setups may be of some advantage, but I doubt it. In the final analysis, they are absolutely better than no filter at all.
  3. alchemy
    Joined: Sep 27, 2002
    Posts: 15,151


    I use a stock filter and change it every thousand miles or so. It seems like the oil is dark the day after I change it, so I'm not sure how much good the filter does.
  4. We use stock filters on our three flathead cars. Didn't have to install them as they came with the engines. Change every few thousand miles. These are older engines and yes the oil gets dark immediately. On a freshly built engine, it would be good to see just how long the oil would be clear......???
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  5. Flathead Dave
    Joined: Mar 21, 2014
    Posts: 2,779

    Flathead Dave
    from So. Cal.

    Some don't run filters at all. They change the oil frequently.

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  6. plym49
    Joined: Aug 9, 2008
    Posts: 2,797

    from Earth

    My suggestion is to never run a road draft system as they can suck grit right into the crankcase. With or without a partial bypass filter, that is a recipe for disaster and is my personal opinion as to why old cars had so many problems with wearing out rod bearings. It's easy enough to hide a PCV system.
    Joined: Dec 3, 2002
    Posts: 1,110


    I usually don't run any filter at all on mine. I just took one off of the 50 engine in my 31 pick up. But I only drive around town, probably a 1000 miles or so a year and change the oil every year. It hasn't been a problem for me. I don't like looking at them on a hot rod, at least on the firewall or front and center on the engine.

  8. Bandit Billy
    Joined: Sep 16, 2014
    Posts: 6,310

    Bandit Billy

    No filter on my 471 blown 8BA. I asked Mike at H&H, this is the recommended method. Filtration reduces oil pressure (already an issue), change the oil, deal with it.
    3340 likes this.
  9. Rusty O'Toole
    Joined: Sep 17, 2006
    Posts: 9,064

    Rusty O'Toole

    Short answer: Any filter is better than no filter.

    Slightly longer answer: There was a LONG discussion of this on an antique car board. One guy who chimed in was a Studebaker expert. He said he had torn down and rebuilt hundreds of Studebaker V8s over the years. Studebaker used a bypass filter up to 1961, full flow for the last few years of production. In his experience there was NO difference in engine wear or length of service. The full flow engines command a premium price, but for his money, he would take the bypass engine as it is just as good and cheaper.

    As to the bypass not filtering all the oil that is nonsense. It filters all the oil every 10 or 15 minutes, just not all at once. Think of a swimming pool filter. It is a bypass type and will filter a pool full of murky water sparkling clean given enough time.

    And the bypass is a finer filter and removes smaller dirt particles. With a full flow the smallest dirt circulates forever and never gets filtered out. A good bypass filter catches everything.
    p__moore, tubman and Raunchy like this.
  10. Woodster
    Joined: Nov 14, 2012
    Posts: 179

    from NorCal

    New to flatheads and was wondering the same thing. My 8BA came with the type of filter that bolts to the engine with screw on top but it's not on the engine and was wondering if it was worth hooking up. Looking at the schematic it appears that it bleeds off some of the oil from the pump and runs it through the filter but it seemed like that would lower the oil pressure. I have the Vern Tardel flathead rebuilding book and they make no mention of adding an oil filter.
  11. Raunchy
    Joined: Apr 16, 2007
    Posts: 373


    I agree with Rusty Otoole and will be running bypass filters on my flatheads. Also they were recommended by Gary Mcglasson who did the work on the Joe Abbin blown motors. I have a Pontiac 370 in and old roadster that they blocked off the filter because of frame clearance. I found a tilted filter adapter and added a filter. Noticed a dramatic difference in the cleanliness of the oil and a smoother feel on your fingers from oil on the dipstick. I will always run a filter on my stuff. Anything is better than nothing for me. But weigh in the opinions and make the decision for yourself.
    mason-d likes this.
  12. Petejoe
    Joined: Nov 27, 2002
    Posts: 10,406

    from Zoar, Ohio

    I use Positive crankcase ventilation to keep the oil clean. Change every 500-1000 miles. Pcv's are much more effective than any bypass filter.
  13. I run a 100% full-flow system - wanted all oil to be filtered before it hits the bearings. With that said, I'd have no problem running a bypass type filtration system - just make sure you have the restrictor orifice in it. I believe that having a filter has to be a good thing - every modern engine you buy has one (good enough for me).
  14. Rusty O'Toole
    Joined: Sep 17, 2006
    Posts: 9,064

    Rusty O'Toole

    Most stock bypass filters take the oil from the pressure relief valve, that is normally dumped back into the crankcase, and run it through the filter first. But some take oil from the oil gallery.
  15. On our Ford Flatheads (needed to specify that!), the input source to these filters is directly from the oil galley (back of the block). Other than the rear main, this is the main output area from the pump.
    Last edited: Feb 22, 2017
  16. Los_Control
    Joined: Oct 7, 2016
    Posts: 616

    from TX

    Ford is not the only flathead in the game :p
    Rusty O'Toole likes this.
  17. Rusty O'Toole
    Joined: Sep 17, 2006
    Posts: 9,064

    Rusty O'Toole

    Thanks Los Control
  18. Bandit Billy
    Joined: Sep 16, 2014
    Posts: 6,310

    Bandit Billy

    I don't mean to argue this point as my flathead knowledge and experience is just getting started and I respect those that have lived them. But here is the pro and con of the argument that I have had many times while building my 335 HP flathead.

    CON: I asked Mike at H&H that exact question, the response was in his opinion that the filtration system reduces the inherently low oil pressure to the point that any filter could be a detriment. He said it is a matter of the good the filter can do (by pass stock filtration) for the system pressure drop it causes. In his mind and a few others that I researched prior to building my motor that it was not necessary with regular and frequent oil changes. Mike also pointed out that my hot rod is not being built as a daily.

    PRO: This is from Joe Abbin's book, the bible of flathead building.
    Sidebar Information:
    How much oil does the Ford Flathead oil pump circulate and how much gets filtered?
    The stock Flathead oil pump is a positive displacement gear type, capable of circulating about 15 quarts per minute under ideal conditions when the engine is spinning at 2,000 rpm (the high-volume version pumps approximately 20 percent more). A recent test at Roadrunner Engineering demonstrated that a stock ’46-53 oil filter with restrictor flows about a quart and a half of oil per minute through a clean filter under meaningful conditions of oil pressure (55 psi), temperature (180 degrees F), and viscosity (15W-40). This means that about 10 percent of the oil pumped by the stock pump goes through the filter under these conditions and the rest goes unfiltered to the engine. Therefore, under these same conditions, I estimate that all the oil in a 5- or 6-quart system is filtered in less than five minutes at highway speeds. Not bad and certainly worthwhile!

    I am still open to the discussion and watching this thread with great interest. I have enough money in this flathead to build 3 or 4 SBC's. I don't want to make a mistake over oil filtration.
  19. Keep in mind that Mike at H&H is talking about a filtration system that is a bypass system. So, while it may reduce the pressure a bit, another way to think about it is that the flathead only has 3 mains, 3 cam bearings and no rockers. They just don't need a lot of flow or pressure on the street, with street clearances and good quality oil. Now if you were running really large racing clearances and a lot of boost (think Bonneville) - I'd switch over to a dry sump and push the pressure to 100 - 120 lbs.

    The system on mine is a full-flow, so I am not bleeding off oil pressure into the pan (like a bypass does). To give you an idea - at the bottom of my filter setup (the outlet side), I have between 80 and 90 PSI at fast idle when cold (this beast idles at about 1150), once it is hot, the oil pressure is at about 65 lbs at idle. That is more than I need - no question about it.

    As I'm sure you're running the 49-53 oil pump, you'll have more than enough flow and pressure for a bypass or a full-flow. Given that your engine is already together, it would be much easier to put a bypass on it. Having very clean oil is never a bad thing!

  20. Rusty O'Toole
    Joined: Sep 17, 2006
    Posts: 9,064

    Rusty O'Toole

    It's all according. The old rule of thumb was 10 pounds oil pressure per 1000 RPM. If you have an adequate pump and the bearings are not worn out, the bypass valve will be dumping most of the oil back into the pan at highway speeds anyway. You could always rig up a bypass valve like the one in Los Control's illustration, so the filter is working ONLY when you have excess oil.

    Really, you only need a filter if you want the engine to last. If you have tons of them and can rebuild them for practically nothing who cares if they wear out.
  21. Bandit Billy
    Joined: Sep 16, 2014
    Posts: 6,310

    Bandit Billy

    Correct, built and broken in already. But this subject is one that I have never been completely comfortable with (running no filter). I installed a high volume oil pump, had to do a little pan welding to make it fit. You have me considering bypass again. That's why I log on here, stand on the shoulders of people who know what they are doing and don't try to reinvent the wheel.
  22. You've already got more than enough volume (which is what is the most important thing for keeping the bearings cool), so I can't see any issue with you putting a bypass style filter on it. If it was me, I'd sleep a bit better knowing that I'm keeping the oil a bit more clean.
  23. tubman
    Joined: May 16, 2007
    Posts: 4,863


    Be careful with high volume oil pumps. Under ordinary circumstances, the are not needed and usually a detriment. I had the engine rebuilt on the 327 in my Corvette. Without asking me, they installed a high volume, high pressure "racing" pump. The oil pressure gauge was pegged all of the time, and the amount of oil pumped at high speeds was overwhelming the drain back system in the engine, causing excess oil consumption. I solved the problem by simply replacing that pump with one that conformed to stock specs. My oil pressure and consumption came back to normal. The gears on the HV pump were at least 50% longer that the ones in the regular pump. Anyone who wants one can have mine for the cost of shipping; it's almost brand new.

    When are people going to start to realize that the engineers that designed these engines knew what they were doing? Sure, a race only engine with super wide clearances may need one, but engines built mainly for the street don't. This is one time when folks should realize that my signature is more of a humorous statement than good advice.
    UNCLECHET likes this.
  24. Glenn Thoreson
    Joined: Aug 13, 2010
    Posts: 78

    Glenn Thoreson
    from SW Wyoming

    I always use the stock bypass filter on my flatheads. Plenty adequate for normal use. The main reason folks experience a drastic oil pressure drop with this setup is they don't have the required restrictor fitting in the feed line from the engine. That simple fitting is a must. On another note, the dark (black) oil mentioned is not the fault of the filter. If it gets black as soon as you've changed the oil it's either blowby or sludge buildup in the engine. Most oil will darken to a brown color rather quickly and is not a concern. Black indicates something amiss.
    The black stuff is normally carbon particles too small to filter out. They don't usually have any adverse effect.
    If it is sludge, filtering will not normally remove enough of it to make a difference. These engines can produce an amazing amount of sludge sometimes.
    One thing more, if the engine is a 59 series they have so many places for the oil to ooze out there is not much pressure to begin with. Using modern water pumps that have sealed ball bearings and plugging the stock relief valve will up the pressure pressure some. Compensate with an 8BA pump with a built in relief. Long post. Sorry. I need a nap now..........

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