A Guide to David Brown Wet Cylinder Liners
- Jan 31
- 4 min read
Updated: Feb 2
Wet liners were a feature of all early David Brown 4 and 6 cylinder engines. There are only two bore sizes, 3 ½ inches and 3 5/8 inches, but there are many other variations, not all of them being obvious. These are listed below in chronological order as there were no differences between the liners fitted to TVO, petrol or Diesel engines at any given time.
Be aware that many tractors no longer retain their original engine block; there’s no easy way of identifying which liners are installed without removing one and measuring it. Unlike some suppliers, we don’t refer to “straight” or “stepped” liners; this is too simplistic, a step can be found on all liners, whilst others fall beyond this description anyway.
In all cases, the top of the liner should be slightly higher than the top surface of the engine block. If the liner has a completely flat top surface, this protrusion should be 5 to 8 thou. inch (0.125 to 0.2mm). Later liners, including current new ones, include a ridge on the top to improve sealing on Diesel engines. These liners should be 3 to 5 thou. inch (0.07 to 0.125mm.) above the block face, taking the reading from the flat surface of the liner. Adjustments can be made by using either 10003 or 1003A copper rings under the liner rim. Both these copper rings and the lower liner seals should be coated in Wellseal upon final assembly.
1939 to 1947.
The VAK1, VIG1 (WW2 aircraft tugs) and VAK1A were fitted with the 10041 liner. If the engine block has either one or two small coolant drain taps it will be fitted with these. The VAK1A also uses these liners in an engine block fitted with a large, central drain tap behind the carburettor, as fitted to later blocks. This liner uses a single lower seal that seats against a shoulder on the liner, as opposed to a pair of seals in grooves used on all subsequent liners. This design relies on downward pressure from the liner when the cylinder head is tightened down to achieve a seal. To determine the thickness of lower seal required, first install the liner with the appropriate thickness of top (copper) ring and no lower seal to achieve the correct top protrusion. Then re-fit the liner with a 4.5mm. thick lower seal and check the top protrusion again. This should exceed the first reading just enough to compress the ring a little when the head is tightened. Following the installation of all four liners, with all seals coated in Wellseal, clamp them down temporarily to prevent upward movement during piston installation. This can be done using large diameter flat washers on adjacent head bolt/stud holes, using spacers on the head bolts, or by using shorter bolts if you have them.
1947 to 1950.
Early Cropmasters, (with a temperature gauge at the front of the bonnet), were the first David Browns to use liners with two liner seal grooves. These liners are 3½ inch bore; they were also fitted to the first Diesel Cropmasters. The outside diameter, adjacent to the seal grooves, is exactly four inches. The relevant engine block is part number 34229.
1950 to 1953
Later Cropmasters. The introduction of the Super Cropmaster in 1950 brought with it the introduction of the 3 5/8 inch bore. This bore size was also used in Diesel Cropmasters from July 1952, from serial number PD 15513, and the 30C, 30D, 50D, 30TD and 50TD. To ensure adequate wall thickness at the bottom of the liner the outside diameter was increased from the 4 inch dimension for the 30375 liner to 4.124 inches. The original flat top versions are part number 65961, the later, ridged top versions are part number 900132. During this era, from 1950 to 1953, the same engine block was used on other Cropmasters, but with 3 ½ inch bore cylinder liners. The flat top versions are part number 38138, ridged top liners are part number 900131.
1953 to 1965.
The diameter of the holes in the bottom of all engine blocks was reduced from 4 5/8 inches to 4.075 inches to reduce the risk of the block cracking between cylinders 1 and 2, also between 3 and 4; boring the blocks to 4 5/8 inches had been found to worsen this problem, allowing coolant to contaminate the oil. To maintain wall thickness at the bottom of the liner the depth of the seal grooves was reduced and thinner section seals used. Again, there are 4 versions of liners that fit these engine blocks. 3 ½ inch liners are part numbers 67172, flat top, and 900084, ridged top. Common applications are – late 25 and 25D, also the 850. 3 5/8 inch liners are 67158, flat top, and 902001, ridged top. Applications include late 30D’s and 50D’s, 900’s, 950’s also 4 cylinder 880’s.
Converting 25D’s and 850’s.
New 3 ½ inch Diesel pistons were discontinued many years ago. In the event of an engine rebuild requiring new pistons the engine can be converted to 3 5/8 inch bore using the appropriate liners (either 900132 or 902001). The only other alteration required is the use of a 3 5/8 inch head gasket.
1961 to 1968.
A wet liner with an longer 3 5/8 inch bore, identified as part number 906859, was utilized in the 4/47 engine, which was only fitted to 990 Implematic and early 990 Selectamatic tractors.
Early 3 cylinder engines, as fitted to late 880 Implematics and red 770’s, were fitted with dry liners; these are beyond the scope of this article.
Later 3 and 4 cylinder engines were fitted with a cast iron sealing ring at the top of the bore. These are slightly raised above the top surface of the block to improve sealing and should not be confused with wet liners.
A small selection of liners that can be found on our website
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