Break-In Basics
The lobe and lifter face of any flat-tappet camshaft is hardened to a certain degree, and a specific break-in procedure produces a distinct polishing pattern on the contact surfaces of the two. This pattern should remain for at least the duration of the engine's life, but if abnormal wear passes through the hardened portion of the lobe and/or lifter, camshaft failure is inevitable.
No direct lubrication is provided to the contact surfaces of the lobe and lifter, but they are indirectly lubricated by oil seepage from the lifter bores and splash oiling from the crankshaft. During installation, both surfaces should be coated with a specific camshaft break-in lubricant. This lubricant is of higher viscosity lubricant. This lubricant is of higher viscosity and is designed to prevent the scuffing that would otherwise occur during cranking and before normal oil circulation begins at initial start-up.
As quickly as the engine fires, its speed should be mechanically increased towards 2,500 rpm and maintained for several minutes. The added rpm is necessary because it promotes high rates of pressurized oil circulation and splash lubrication. It also forces the lifters to rotate quicker on the lobes thereby enhancing the polishing effect, and is believed to lessen the overall inertial load on the camshaft.
Proper break-in should take 25 to 30 minutes to complete. During that time, the engine should never be run at idle speed. Oil pressure and coolant temperature must be closely monitored and the engine should be immediately shut down upon the first indications of problems. There's little harm in interrupting the break-in process to allow the engine to cool. Once the problem is fixed, the engine is restarted and the process can continue until the camshaft supplier's suggested run time has elapsed.
Next, we removed the timing...
Next, we removed the timing cover, valley pan, and valve covers, using care with the timing cover to prevent the loss of the two alignment guides on each of the lower front bolts. We immediately stuffed a shop rag into the open edge of the oil pan under the crank gear to prevent small parts from accidentally falling in.
After removing the rocker...
After removing the rocker arms, pushrods, lifters, and fuel pump eccentric, we used a pry bar to gently pry the cam gear off, which was followed by the entire timing chain assembly.
The lobes and journals of...
The lobes and journals of the new camshaft must be thoroughly coated with the supplied break-in lubricant prior to installation. We found it easiest to coat the first set of lobes while the camshaft was out of the engine, and then insert it as far as the first two journals, coat the second set of lobes, and insert it further. We repeated this process until the camshaft was completely coated and fully installed. It should rotate by hand once in place. A camshaft installation tool can be a great help when trying to align the rear journal.
We then removed the camshaft...
We then removed the camshaft thrust plate and slowly rotated the cam as we carefully extracted it from the block, using care not to damage its soft bearings in the process. (Don't yank or twist it sideways-serious cam bearing damage can result. Don't be alarmed, though, if you see slight marks or scratches on the bearing surfaces. Be sure to remove the cam key and install it onto the new unit too.)
The camshaft thrust plate...
The camshaft thrust plate not only prevents the cam from walking forward, it also provides direct lubrication of the timing chain assembly. We used caution to ensure it was installed correctly-the machined groove goes towards the camshaft and the spurt hole faces outward.
When speaking of timing chain...
When speaking of timing chain sets, a common phrase often heard during installation is to "align the dots." But what exactly does that mean? The gears of the timing set contain small dots on the perimeters that provide correct cam-to-crank phasing when the dots are vertically aligned. When the No. 1 and No. 6 pistons are at TDC, the crank gear dot should be in the 12:00 position. Some installers then position the cam gear at 6:00, while others prefer it at 12:00. Though either position is acceptable, the engine firing points are 180 degrees different, depending on whether the cam gear is at 6:00 or 12:00. Since our distributor was marked for No. 1 firing during disassembly, we positioned both dots at 12:00.