The crankshaft and camshaft assemblies are the heart of the XPAG and XPEG engine. The crankshaft in particular demands more careful assessment than any other single component in a TD or TF rebuild. The three-bearing design is fundamentally less rigid than the five-bearing arrangement used in the later B-series engine, and this has significant implications for both longevity and rebuild strategy.
The Crankshaft
The XPAG and XPEG crankshaft is a three-bearing forged steel unit running in shell bearings. The crankshaft itself is common between the XPAG and XPEG engines, the journal diameters and bearing specifications are identical.
However, it is the most critical wear item in the entire engine, and its condition must be assessed by a specialist before any rebuild proceeds. Crack testing is essential, as fatigue cracks can develop in the journal fillets without visible evidence. The crankshaft material specification was improved from engine number XPAG/TD2/27551 in April 1953, and earlier crankshafts remain the most vulnerable. A crankshaft that passes crack testing can typically be reground to the next undersize, main and big end bearing shells are available in seven sizes from standard through to sixty thousandths undersize.
New crankshafts are available but represent a significant investment. Reground exchange crankshafts, where the customer's own unit is professionally reground and returned, offer a more economical route provided the original is within regrinding limits. The spigot bush that locates the gearbox input shaft in the rear of the crankshaft, the Woodruff keys, the crankshaft sprocket, oil thrower, pulley, starting dog bolt with its washer, and the rear main bearing cap oil pipe should all be assessed during any rebuild. Main bearing cap studs and nuts are universal across all XPAG and XPEG engines.
Flywheel and Ring Gear
The flywheel is one of the key components affected by the TD2 engine change in July 1951. Early TDs to engine number 9407 use a smaller flywheel sized for the original 7¼-inch clutch, with a ring gear of 10?-inch internal diameter. From engine number 9408, the TD2 and all TF engines use a larger flywheel for the 8-inch clutch, with a ring gear of 10¾-inch internal diameter. These flywheels and ring gears are not interchangeable.
Flywheels are reconditioned on the customer's own unit basis, with the ring gear renewed as part of the process. The flywheel-to-crankshaft bolts and dowels, and the clutch cover dowels that locate the pressure plate assembly to the flywheel, are common across all variants.
Camshaft and Timing Components
The camshaft is a chain-driven unit operating the valves through cam followers, push rods, and the rocker assembly. The standard camshaft was used throughout TD production until engine number XPAG/TD2/24116 in January 1953, when a revised camshaft with new valve timing was introduced to provide improved torque at lower revs. This revised camshaft was subsequently adopted as the standard fitment for the TF, and the change was accompanied by a new tappet clearance plate fixed to the rocker cover. The tappet clearance itself was altered from 0.019 to 0.012 inches, a significant difference that must be confirmed against the engine number before adjusting the valve clearances on any TD or TF engine. The camshaft bearing set, centre and rear bearing bolts, front thrust plate with its bolts and spring washers, and the rear circlip are shared across all XPAG and XPEG engines.
The camshaft sprocket, oil thrower, sprocket washer, bolt, and tab washer are also universal. The timing chain and sprocket kit, comprising the chain and both crankshaft and camshaft sprockets, is universal across all TD and TF engines, and is available either as a complete kit or as a separate chain. The timing chain tensioner assembly, or its individual components (pad, spring, and bolt), maintains correct chain tension and should be renewed during any rebuild. A worn chain and tensioner causes retarded valve timing, rough running, and a characteristic rattle at idle.
Cam Followers and Push Rods
The eight cam followers are universal across all XPAG and XPEG engines. They run directly in bores machined into the block. The push rods changed in length between engine numbers XPAG/TD2/17297 and 17298 in June 1952, when shorter push rods with correspondingly longer rocker adjusting screws were introduced. Push rods should be checked for straightness during any rebuild, and the correct length must be established by reference to the engine number before ordering replacements.