REMOVAL & INSTALLATION
6-240 (3.9L) and 6-300 (4.9L) Engines
If it is necessary to remove a rocker arm stud, Tool T79T-6527-A is available. A 0.006 in. (0.15mm) oversize reamer T62F-6527-B3 or equivalent and a 0.015 in. (0.38mm) oversize reamer T62F-6527-B5 or equivalent are available. For 0.010 in. (0.254mm) oversize studs, use reamer T66P-6527-B or equivalent. To press in replacement studs, or use stud replacer T79T6527-B or equivalent for 6-300 (4.9L). Rocker arm studs that are broken or have damaged threads may be replaced with standard studs. Loose studs in the head may be replaced with 0.006 in. (0.152mm), 0.010 in. (0.254mm) or 0.015 in. (0.38mm) oversize studs which are available for service. Standard and oversize studs can be identified by measuring the stud diameter within 1
in. (28.6mm) from the pilot end of the stud. The stud diameters are:
0.006 in. (0.152mm) oversize: 0.3774-0.3781 in. (9.586-9.603mm)
- When going from a standard size rocker arm stud to a 0.010n (0.254mm) or 0.015n (0.38mm) oversize stud, always use the 0.006 in. (0.152mm) oversize reamer before finish reaming with the 0.010 in. (0.254mm) or 0.015 in. (0.381mm) oversize reamer.
- Position the sleeve of the rocker arm stud remover over the stud with the bearing end down. Thread the puller into the sleeve and over the stud until it is fully bottomed. Hold the sleeve with a wrench; then, rotate the puller clockwise to remove the stud. If the rocker arm stud was broken off flush with the stud boss, use an easy-out to remove the broken stud following the instructions of the tool manufacturer.
- If a loose rocker arm stud is being replaced, ream the stud bore using the proper reamer (or reamers in sequence) for the selected oversize stud. Make sure the metal particles do not enter the valve area.
- Coat the end of the stud with Lubriplate®, or equivalent. Align the stud with the stud bore, then, tap the sliding driver until it bottoms. When the driver contacts the stud boss, the stud is installed to its correct height.
- To remove the rocker arm stud, which is pressed into the cylinder head, put spaces over the stud until just enough threads are left showing at the top so a nut can be screwed onto the top of the rocker arm stud and get a full bite. Turn the nut clockwise until the stud is removed, adding spacers under the nut as necessary. Rocker arm studs that are being replaced because of damaged threads or are broken off, may be replaced with standard size replacement studs. If the stud is being replaced because it is loose in the head, it may be replaced with 0.006 in. (0.152mm), 0.010 in. (0.254mm) or 0.015 in. (0.381mm) oversize studs. Ream the stud mounting hole with a 0.006 in. (0.152mm) oversize reamer first, before using the 0.010 in. (0.254mm) or 0.015n (0.381mm) oversize studs. Do not allow metal chips to get down around the valves. To install the rocker arm studs, it is necessary to have a rocker arm stud installer tool, which is readily available in automotive parts and supply stores. The Ford tool number is shown in the accompanying pictures.
- Screw the new stud into the installer tool and coat the end of the stud with Lubriplate®. Align the stud and installer with the stud bore and tap the tool until it bottoms against the cylinder head. At this point, the stud is installed to the correct height.
The lifters used on diesel engines require a special test fluid, kerosene is not satisfactory. Remove the lifters from their bores and remove any gum and varnish with safe solvent. Check the lifters for concave wear. If the bottom of the lifter is worn concave or flat, replace the lifter. Lifters are built with a convex bottom, flatness indicates wear. If a worn lifter is detected, carefully check the camshaft for wear. To test lifter leak down, submerge the lifter in a container of kerosene. Chuck a used pushrod or its equivalent into a drill press. Position the container of kerosene so the pushrod acts on the lifter plunger. Pump the lifter with the drill press until resistance increases. Pump several more times to bleed any air from the lifter. Apply very firm, constant pressure to the lifter and observe the rate which fluid bleeds out of the lifter. If the lifter bleeds down very quickly (less than 15 seconds), the lifter should be replaced. If the time exceeds 60 seconds, the lifter is sticking and should be cleaned or replaced. If the lifter is operating properly (leak down time 15-60 seconds) and not worn, lubricate and reinstall in engine. Always inspect the valve pushrods for wear, straightness and oil blockage. Damaged pushrods will cause erratic valve operation.