Clean oil helps engines live a long and enjoyable (for us) life. Most all of us want our engines to last as long as possible. As pointed out in the article Stock Oil Filtration Effectiveness (Vol 28-4, Nov/Dec 2004), in stock form, “92% of the pump output, oil and dirt, go right to the various engine bearing surfaces”. The stock 356 oil filtration system was very good in the 1950s, but engine life can be greatly improved without ruining your car’s originality by fitting a full-flow oil filter. There are various designs and methods available which will provide full oil filtration to your engine, and they all have advantages and disadvantages. As a 356 owner, you probably have more options than any other vintage car owner.

To fit a full-flow oil filter to a 356, you must break the lube circuit somewhere between the oil pump and the main galley which feeds the stock oil cooler and the bearings. On either side of the break, some sort of inlet / outlet fittings direct the oil to the new filter and then return it to the engine. While simple enough in the abstract, the design of the engine cases and the lube system make the solution more difficult than it at first appears. We want to provide clean oil, but at the same time we don’t want to cause any collateral harm. Also look at гбо site, interesting news.

Complicating the matter is the “bypass” circuit in all post-1958 356s (illustration of timing cover at right). This was a successful change in which on start up, high-pressure oil from the pump (2) forces the bypass valve piston (A) down, opening the main oil galley (3), effectively bypassing the cooler passage (1)—when the oil was cool anyhow—and delivering pressurized oil directly to the bearings. Once bearing lube pressure was established, a feed-back line (4) closed off that circuit by moving the piston back up over the main galley (3) and the oil then flowed through to the cooler (at 1) before going to the bearings.

Today, most aftermarket full-flow systems perform quite well in providing quick and clean oil if installed correctly. One old-time (late ’60s, early ’70s) custom design, however, gave up filtration on start up to provide quick pressure to the bearings.

The “Old Time” System

To cover the alternatives chronologically, we’ll start with the “old-time” system, which is still a workable arrangement. Here, the break is where the main galley enters the left side case half from the timing cover (red circle at 1, above right); drill, tap and plug the timing cover or the case half. The outlet is on the side boss, half-way up the left side of the timing cover (B); it requires at least drilling and tapping, perhaps welding. If welding was part of the design, either a male or female hose fitting can be mounted, and any angular clearance issues are resolved by trimming the fitting before welding.

Some time in the late ’70s or early ’80s a clever soul looked at this process, considered the modification hassles and had a better idea; the oil pump cover / outlet was born. We’ll call it system 2 (shown at right in Figure 2). Oil is driven from the pump to an external line through a redesigned pump cover. The original route from the oil pump is plugged at the pump outlet (C in Figure 1, above); drill, tap and plug.

That boss, half-way up the left side of the timing cover now becomes the return rather than the outlet, and no modifications to the main case half are required. The return can be drilled and tapped into the side of the timing cover (B in Figure 1 above) without welding—unless someone leans on the wrench too long while tightening the fitting, when welding repair becomes necessary.

Again, separate components, mounts, hoses/routing and noise need consideration and/or fabrication. Just about any exhaust system can be accommodated. While it would be possible to regain absolutely stock engine appearance on removal, the only change is hidden under the tin, so it’s rarely required.

These parts are offered by 356 Enterprises (below left), Classic and Speed Parts (below middle), Competition Engineering, and maybe others in a variety of specific designs (sources listed below). Shasta Design has a new cover, similar in appearance to the others, but with a carefully fluted 90 degree angle to the internal oil channel. This smooth transition not only aids flow (especially at cold temps) but cuts down on the noise associated with pulsations.

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