Oil Bath Pre-Cleaners

RPO K47, Heavy Duty Oil Bath Air Cleaner, first became available in the mid-1963 model year for cars and FCs. Note that it was never offered for any Corvair prior to 1963, including wagons and FCs, although many people have later added them.

This article details the different versions and features of K47 and includes representative photos and Assembly Manual pages for each, as well as production figures for each type, where available. Production figures were obtained from articles written by David Newel as published in the CORSA Communique.

1963

1963 had two versions of K47, the car version and the FC version. The car version simply added an oil bath cleaner to the top of the air intake tube, while the FC version connected a hose from the intake tube to a separate Oil Bath cleaner which was mounted to the right rear corner of the engine. Otherwise, no modifications were made to the regular air filters or PCV system.

This was the car version:

And this was the FC version:

1964

1964 added K47 to AC and Turbocharged cars and changed the design for the other cars. However, the first 5 months of the 1964 model year continued to use the 1963 style K47 which means these 1964 Corvair were equipped with dual air cleaners and PCV valves.

K47 for Air Conditioned cars was introduced this year, and it is a very interesting story. It is clear from changes in the assembly manual and the contemporaneous price chart that Chevrolet originally intended to include the Oil Bath Precleaner with all Air Conditioned cars beginning in 1964, but in December of 1963 they revised their documents to separate it from C64 and make it a separate K47 option:

I believe they planned to add it to AC to provide cooler air to the carburetors, as otherwise they are drawing air from below the condenser shroud. It is worth noting that the Oil bath pre cleaner for 1964-65 AC is the only unit that has a snorkel, and it is pointed towards the rear corner of the car; this supports the idea that they wanted to draw cooler air into the carburetors.

As for the reason they backed off, I suspect they ran into a fitment issue and by the time they figured it out they decided to just leave it as an option instead. Sheet D6.00 in the C64 section note 5 (dated 1-13-64) indicates that the Receiver/Dryer should be moved rearward approximately 2.22″. The only reason to move it backwards is to provide clearance to mount the Oil Bath Aircleaner. I checked this out on my 1964 Convertible with Factory AC, build date 09C, and confirmed that you cannot mount the Oil Bath Cleaner in the spare tire well unless the receiver dryer is moved to the rearward position (which obviously had not been done on my car). These facts, taken together, strongly suggest that the AC K47 may never have been installed prior to late December 1963 or early January 1964. We also know from Dave Newel’s research that only about 6% (344) of all 1964 cars with AC (6010) also had the K47 option, so that fits with it having been offered later in the year.

Around December 1963, the system for non-AC cars was redesigned. The re-design moved the Oil Bath cleaner to the left rear corner and connected it to a single central air cleaner via a short rubber hose. This design also necessitated a new upper PCV tube (Item 5, part number 3851850). This tube is shorter than the standard (95/110HP) tube (part number 845686). The shorter tube is required because the Oil Bath air cleaner snorkel is turned towards the left rear corner, vs the standard air cleaner which is turned toward the right rear, and GM desired that the tube enter the air cleaner on the opposite side from the snorkel.

With the Oil bath redesign, the option was added for the Turbo engine. The K47 turbo Air Cleaner snorkel was elongated and rounded at the tip to mate with a rubber hose connecting it to an enlarged outlet on the oil bath cleaner (which otherwise used the same parts as non-turbo K47). No revision to the turbo PCV system was required for the Turbo K47.

FCs in 1964 continued to use the same FC design, so there were 5 versions of the Oil Bath Pre-Cleaner in 1964. Total production for each type indicated in picture caption:

1965

Design changes were only slightly altered for 1965. Mostly, they involved changes to the mounting brackets for the Oil Bath cleaners to accommodate the changes in the body of the car. Instead of the bent straps used to mount the oil bath in the 1964 cars, they used a tripod mount for the non-AC cars and a stamped Steel bracket for the AC cars.

The PCV tube for the basic style was shortened slightly and the notches in the air cleaner crossover tube widened to permit slight clockwise rotation of the air cleaner to line up its snorkel with the more lateral position of the oil bath cleaner.

The basic style of K47 was offered for both 2 and 4 carbureted engines, the only real difference between the two being the 4 carb version continued to use the Chrome air cleaner top; otherwise they were identical, both using the single snorkel K47 air cleaner and the shorter PCV tube.

The AC version of K47, was, with the exception of the mounting bracket, unchanged from the 1964 version and only used with 2 carb engines, as AC was not available with the 4 carb engines this year.

An additional option, K46 (“Desert Air”) was added this year. It consisted of a special shroud to direct air into the engine and included the K47 option. However, because of the shroud, this version of K47 used yet another uniquely shaped PCV tube

Because the Greenbriar was still offered this year, 1965 has six variations of the Oil Bath pre cleaner. Total production for each type indicated in picture caption:

1966

In 1966 FCs were no longer offered and the changes made to Air conditioning eliminated the need for a separate AC version of K47, but the A.I.R. system was added to California cars, introducing a slightly new variation in which the PCV tube connects to the Carburetor intake tube (tube connecting air cleaner to the carburetors), instead of to the Air Cleaner. However, they continued to produce the version that connects to the Air Cleaner for non-A.I.R. cars through 1967.

1966 had 6 versions of the Oil Bath Precleaner. Total production for each indicated in picture caption:

1967

The Turbocharger and K46 Desert Air were discontinued in 1967, so there were only 4 Oil bath pre cleaner versions that year – 2 carb or 4 carb, each with or without A.I.R. Any one of these could theoretically be combined with AC as well, but there is no evidence that they ever were, as A.I.R. and AC only existed together for a very brief time in 1967 so it’s quite unlikely that you would ever find that combination at all, let alone with Oil Bath added. Production totals for 1967 K47 are noted in picture captions – mostly unknown.

1968

All cars produced in 1968 and 1969 used A.I.R., so there were only two version of K47.

Production figures in photo captions:

1969

As in 1968, only two versions of K47 remained.

Production totals are in photo captions:

Filter Element

Steve Spilatro provides the following detail about the FC Oil Bath Filter Element.

The FC filter elements had an organic, possibly jute fibrous packing.  There are filters available online that have a metal fiber packing, but they may be a later GM or after-market product.  This table shows what I know about the unit part numbers, as extracted from the Parts Manuals

	Air Cleaner assembly	base unit	cover unit	filter element	Production*
1963	5649631	5649849	?	1544871
1964	6419943	6420122	6421223	1544871	3935
1965	6420552	6421311	?	6421285	?

*production data is from Dave Newell’s recent article in the March 2024 Communique, p 22.

Part numbers for the ’63 and ’65 covers are not given in the Parts Manuals.  These manuals are notoriously incomplete and often inaccurate; however, that the ’64 base and cover unit numbers correspond indicates that this was a new cover.  How it differed from the earlier version is unknown and possibly was also used in ’65.  The redesigned base unit in 1965 (or possibly late ’64) corresponded with a new filter element that incorporated a metal baffle on the bottom as shown in the pictures below.

When was Oil added to the Unit?

It’s somewhat interesting to ask this question, given that the 1963 and 1964 pages for K47 (FC, Turbo, and Cars without AC versions) all indicate a tag was placed on the steering wheel telling owners to add oil before operating the vehicle, and yet they also include a lubrication flag telling the assembly line workers to add the oil. Strangely, the FC assembly manual page adds this statement: “Tag – for all Models not driven away, attach to steering wheel.”, but that statement is not added to the car pages until 1965. Another oddity, neither the tag nor the lubrication flag appear on the 1964 page for the oil bath option for air conditioned cars. In 1965 the lubrication flag appears, but the tag is still not indicated on the AC-oil bath page. So, did the assembly line add oil to the oil bath air cleaners for cars or not? Did they perhaps add oil to the AC versions and not to the others because the AC oil bath cleaners have a sealed top and the others do not? It’s not unreasonable to imagine that oil added to the cleaners with unsealed tops could make quite a mess in transportation. In any event, it’s an interesting question and one we will probably never answer unless additional documentation surfaces.

Summary

These next three tables summarize the part numbers for the various K47 options. The numbers in the hashtag (#) columns refer to the number identifying the part in the drawings for that particular year’s assembly manual. The part numbers are the original GM numbers as found in the Assembly manuals. I color coded the part numbers to identify part numbers that stayed the same or changed. Click on any photo to enlarge it

This final table summarizes the model year availability of the various versions of K47 and indicates total production of each, where known. All information is believed to be correct but subject to revision if further data is submitted.