24 Volume 28, Number 6

Clean oil helps engines live a long andenjoyable (for us) life. Most all of uswant our engines to last as long aspossible. As pointed out in the article Stock OilFiltration Effectiveness (Vol 28-4, Nov/Dec2004), in stock form, “92% of the pump output,oil and dirt, go right to the various engine bearingsurfaces.” The stock 356 oil filtration system wasvery good in the 1950s, but engine life can begreatly improved without ruining your car’s origi-nality by fitting a full-flow oil filter. There are var-ious designs and methods available which willprovide full oil filtration to your engine, and theyall have advantages and disadvantages. As a 356owner, you probably have more options than anyother vintage car owner.

To fit a full-flow oil filter to a 356, you mustbreak the lube circuit somewhere between the oilpump and the main galley which feeds the stockoil cooler and the bearings. On either side of thebreak, some sort of inlet/outlet fittings direct theoil to the new filter and then return it to theengine. While simple enough in the abstract, thedesign of the engine cases and the lube systemmake the solution more difficult than it at firstappears. We want to provide clean oil, but at thesame time we don’t want to cause any collateralharm.

Complicating the matter is the ‘bypass’ cir-cuit in all post-1958 356s (illustration of timingcover at left). This was a successful change inwhich on start up, high-pressure oil from thepump (2) forces the bypass valve piston (A)down, opening the main oil galley (3), effectivelybypassing the cooler passage (1)—when the oilwas cool anyhow—and delivering pressurized oildirectly to the bearings. Once bearing lube pres-sure was established, a feed-back line (4) closedoff that circuit by moving the piston back up overthe main galley (3) and the oil then flowedthrough to the cooler (at 1) before going to thebearings.

Today, most aftermarket full-flow systemsperform quite well in providing quick and cleanoil if installed correctly. One old-time (late ‘60s,early ‘70s) custom design, however, gave up fil-tration on start up to provide quick pressure tothe bearings.

Different ApproachesTo cover the alternatives chronologically,

we’ll start with the ‘old-time’ system, which is stilla workable arrangement. Here, the break iswhere the main galley enters the left side case halffrom the timing cover (red circle at 1); drill, tapand plug the timing cover or the case half. Theoutlet is on the side boss, half-way up the left sideof the timing cover (B); it requires at least drillingand tapping, perhaps welding. If welding was partof the design, either a male or female hose fittingcan be mounted, and any angular clearance

issues are resolved by trimming the fitting beforewelding.

The return is on the left side case half, top,far left, rear; you can see a plug on top of the case.This requires drilling, likely welding and perhapsmachining the cases as a result of possiblewarpage during the welding. Again, the ‘sex’ ofthe fitting and the physical direction can be driv-en by other requirements.

As mentioned, this system delivers un-fil-tered oil at start up (let’s call it a 99.9% full-flow),but delivers pressure to the bearings quicklyregardless of any fill-up time required by the cool-er/filter system. It also offers design flexibility, andas a result was used on racers of that vintage.Given the flexibility, this system can be fitted to anytach-drive arrangement or exhaust system.

It does require hoses and various compo-nents/mounts (like a remote filter head and/orcoolers) plus the artful routing of the hoses. Andthere are other design issues related to noise.There’s no reasonable chance the engine can bereturned to stock appearance.

The parts are available from any speed shopor race car parts seller, but the design and fabri-cation labor is either yours or bought from theshop you use.

The Pump Cover Outlet SystemsSome time in the late ‘70s or early ‘80s a

clever soul looked at this process, considered themodification hassles and had a better idea; the oilpump cover/outlet was born. We’ll call it system2. Oil is driven from the pump to an external linethrough a redesigned pump cover. The originalroute from the oil pump is plugged at the pumpoutlet (C at left); drill, tap and plug.

Full-Flow OilFiltration and the356 Lube System

The bypass oil system. The plunger (A)would cover the main oil galley (3) duringwarm operation.

By Ron LaDow

The “old time” system (let’s call it system 1) has anoutlet on the third piece at B, below left. The returnis on the case as shown above.

March / April 2005 25

That boss, half-way up the left side of thetiming cover now becomes the return rather thanthe outlet, and no modifications to the main casehalf are required. The return can be drilled andtapped into the side of the timing cover (B) with-out welding - unless someone leans on thewrench too long while tightening the fitting, whenwelding repair becomes necessary.

Again, separate components, mounts,hoses/routing and noise need considerationand/or fabrication. Just about any exhaust systemcan be accommodated. While it would be possibleto regain absolutely stock engine appearance onremoval, the only change is hidden under the tin,so it’s rarely required.

These parts are offered by 356 Enterprises,Classic and Speed Parts, Competition Engineering,and maybe others in a variety of specific designs.Shasta Design has a new cover, similar in appear-ance to the others, but with a carefully fluted 90degree angle to the internal oil channel. Thissmooth transition not only aids flow (especially atcold temps) but cuts down on the noise associat-ed with pulsations.

Pump cover modified for outlet, system “2.” Return isat boss on third piece, where outlet is on system 1.Below from left: CSP unit, Skirmants’ unit with inte-gral pressure relief, welded tach drive cover.Bottom: The original oil system, shown at op temp,and a sysytem 2 with external filter and cooler.

Some are provided with internal reliefs,some to fit mechanical-tach cars, etc. For reasonsthat escape me, many seem to need modificationto the engine tin where more careful designwould make none required. Again, the overall sys-tem design and labor do not come with the parts.

An improved pump cover designSeveral years ago, a new design took a bit

better advantage of the given engine features inpost ’60 (‘large-pump’) engines. Here the breakand the inlet/outlet happen within the oil pumpitself. A clearance ‘notch’ is cut and hidden insidethe pump cavity, and there is no other modifica-tion nor any possible need of welding. The ‘returnfitting’ is also the ‘plug’, breaking the circuitinside the pump cavity. The engine has no exter-nal changes, so any later return-to-stock meanssimply replacing the original pump cover onremoval of the system. Unlike some of the otherpump cover outlets where the round sheetmetalpulley cover interferes with the center of the coveroutlet, no additional tin clearancing is required.

This technology is applied to two separate

26 Volume 28, Number 6

http://members.rennlist.org/eric_nichols/, Orper Bruce Baker, mount a pressure switch at thecoil to prevent engine starting until the bearingshave oil pressure.

Almost all full-flow systems will yield areduction in engine oil temperatures, since thesurface area of the lube system exposed to coolair is increased. But too cold is as bad as too hot;consider that engines need some reasonable tem-perature to expand the parts to running clear-ances. If you will hang that 28-row oil cooler inthe nose, consider a thermostatic by-pass valve.Coolers also need careful selection, as do filters.Fresh, cold, large-pump 356 engines can easilysurpass 300 psi oil pressure near the pump out-put. Most coolers and filters are not designed forthat amount of pressure, and certainly the cheap-est of the lot are not.

Regardless of the system, budget somewherein the range of $500 to $1,000 for a complete sys-tem done with good quality parts and materials.Talk to the parts suppliers and/or the shop youuse, but compare that to the cost of a crankshaftor early rebuild.

Like planting a tree, the best time to fit goodfiltration is either 10 years ago or right now. Anengine rebuild is the obvious opportunity, butengines with some thousands of miles on themcan live a longer usable life by adding it now. Mostsystems require removal of the engine or at leastthe timing cover for installation. The PrecisionMatters units are designed to allow installationwith the engine in the car, but even those are eas-ier to install with the engine out. If done during arebuild, add anywhere from one hour to a weekor so to the time frame, depending on the system.

With all the options available, your enginecan have the benefits of truly clean oil. The vintageof your engine/car and your tastes will decidewhich alternative is the bet fit.

Thanks to Duane Spencer of Shasta Designfor use of photos from his books The CompletePorsche 912 Guide and Porsche 356Performance Guide.

systems. So far, space limitation has resistedapplication to mechanical-tach drives.

The first system has the filter mounteddirectly to the oil pump cover, eliminating anyadditional hoses or components. It was designedfor C-type cars and fits only with electric tachome-ter drives and stock (or similar) exhaust systems.

From top: Precision Matters’ all-in one full flow fil-ter, and their remote oil adapter showing the kit andthe installed unit.

No other design or fabrication is required uponfitting.

The second design is smaller and held clos-er to the timing cover to accept exhaust systemswhich use the space devoted to the filter in thefirst instance. Again, electric tach drive only. Thisproduct requires separate design and mountingof the filter and/or cooler, plus the hoses as perearlier systems. These two are available only fromPrecision Matters or dealers.

Noises OffIf you are planning to use any of the systems

requiring hoses and separate mountings of com-ponents, there are design issues which needattention:

All high-pressure hydraulic pumps deliverfluid in pulses. Because the 356 lube system is, ineffect, a high-pressure hydraulic system, the fluidpulses in time with the pump. Any system withhoses and auxiliary mounts will vibrate in tune,and you won’t like it if they transfer that ‘music’ tothe car’s structure. Pay very careful attention toflex-mounts, avoiding wide, flat panels as mount-ing locations, etc. Mount everything such that theparts and hoses can vibrate a bit without transfer-ring that movement to the car structure.

Other Design IssuesIn all but two systems (the ‘old time’ and the

Precision Matters Full Flow), fill-up of the exter-nal circuit can take time from pressurizing thebearings on start-up. Make that time as short aspossible. If all the components are below thesump fill line, they will never drain and will needno fill-up.

If you mount components higher than that,you might consider a one-way, anti-drain-backvalve to keep them full. Eric Nichols designedsuch a system and posted the design at