>You wrote: >Don,
>
>>So my Ford factory shop manual is wrong then?
>
>>>>What I have heard is the smaller the filter the "sooner" the bypass
>>>>becomes activated. Even largish (PH8A) filters have their bypass
>>>>open at higher RPM (and viscocity) but smaller filters bypass sooner
>
>>>>and you end up spending more time without the filter in the circuit.
>
>Sorry Frank, but I don't think that Fram is so sophisticated with their
>filters that they can incorporate a valve that will bypass oil flow:
Ahh, but they do indeed!
> 1. before the factory relief pressure of 60 psi (more or less,
> because not all springs were created equal). Otherwise the oil
> would "relief" back into the pan.
Nope, the filter bypass does just that, it bypasses the filter. Oil flows
past the filter and into the motor. Ford small blocks also have a primary
relief that discharges into the pump intake at about 60-80 PSI. These
engines do not appear to discharge into the pan at all.
> 2. and not before the normal operating pressure of 50 psi is reached,
> otherwise the "bypass valve" would open and allow unfiltered oil
> to circulate.
Nope, the drop across the filter should be a small fraction of the engine
oil pressure. As long as the filter stays clean and the flow rate low the
drop across it remains below the 8 to 11 PSI and all the oil flows through
the filter. I have heard that most filters bypass partially at higher revs.
>
>That would be a very intelligent filter indeed for only $2 each (local
>Target and K-Mart super sales). Plus, in the few oil filters I've torn
>open, I've yet to see a bypass valve in there.
Well, looking down a PH8A I have in the shop, the bypass valve mechanism
seems pretty obvious to me. Spend 2 bucks and take a look.
BTW, I also have a Fram filter for a '80 Buick Reagel (Yucky pooh, don't
ask!) and it has none. I assume it is in the oil filter adaptor. Many
Buick V8s placed their relif in the front cover/oil filter adaptor assembly.
>
>Don Daves <dondaves@ix.netcom.com>
>Santa Cruz, CA.
>65 Tiger (his)
>64 1/2 Mustang conv. (hers)
Frank Marrone MK I Tiger B9471116
marrone@wco.com 1966 LTD
Series I Alpine (2.3L powered by Ford)
Yamaha Seca 900
|