|Installing and Degreeing an Engine Camshaft -|
In our last segment of the engine build series, we completed the installation of the reciprocating components. This time around, we’ll install the camshaft and degree it. It sounds very racy and technical; but, the truth is, if you can use a dial indicator and can perform simple math (adding a couple of numbers and dividing by two), it’s really a piece of cake. The tools aren’t outrageous in cost (or availability). And, just like all of the earlier segments, the only thing you’ll really need is a big dose of patience. Follow along. It’s a simple process.
As pointed out above, camshaft installation isn’t problematic, but you do have to be careful not to nick the cam or the cam bearings as it goes into the engine. Prior to installation, clean the cam with mineral spirits or solvent. You can use a commercial cam handle or temporarily install the cam sprocket or a long bolt turned into one of the sprocket threads in the nose of the cam. The cam sprocket or the long bolt can be used as an installation “handle.” If the cam is a modern roller profile, there is no need to use cam break-in lubricant on the camshaft. Simply coat the camshaft with engine oil, and using the “handle,” slowly and carefully slide the cam through the cam bearings in the engine.
If the engine is equipped with a flat tappet cam then each camshaft lobe must be coated with break-in lubricant as the cam is installed. We typically coat the lobes in pairs just before they pass through the first camshaft bearing at the nose of the cylinder block.
Remove the cam “handle” and install a new cam drive. If it is a conventional chain, you’ll need to tap the crankshaft drive gear onto the crank. We use anti-seize compound on the crankshaft for this purpose. Using a short piece of tubing (pipe) as a driving tool, tap the gear in place. Install the new chain as well as a new timing sprocket. Check the timing “Pip” mark alignment. In most instances, the pip marks face each other.
It’s a good idea to use thread-locking compound on the camshaft fasteners, but only after the camshaft is degreed (see below). Tighten the cam bolts to the factory specifications and you’re done.
If the engine is equipped with a high tech camshaft drive such as the Jesel Belt Drive shown in the accompanying photos, installation is a bit more complicated. Here’s a brief synopsis: A timing valley cover is first installed on the cylinder block. The nose of the cam has a special adapter installed. Next the cam is installed in the engine. Jesel provides a series shims necessary to set camshaft endplay. Once the endplay is checked with a dial indicator, the lower drive pulley is driven on to the crankshaft (Jesel provides a special driving tool with their belt drive kit).
At this point, the engine is rotated so that #6 cylinder is at Top Dead Center. The camshaft is rotated so that the keyway is at the 12:00 position. The upper pulley is assembled onto the cam adapter (which was bolted to the snout of the cam earlier). You have to tilt the upper pulley slightly (with the belt attached) so that it fits the cam adapter. Tighten to specs and essentially you’re done.
So what does the belt drive set-up offer? The belt drive eliminates crankshaft harmonics having an effect upon valve timing. This provides a measurable increase in engine performance. A belt drive makes cam swaps simple for racers (there’s no need to drop the oil pan or remove a timing cover to make cam changes). At higher engine speeds, plenty of folks feel a belt drive is actually more reliable than timing gears or a timing chain. Those are plenty of benefits from a performance perspective, but the icing on the cake is ease of cam timing changes. Here, you simply loosen four bolts and using the supplied spanner wrench, you can advance or retard the timing. You’ll see more of the Jesel belt drive arrangement in the accompanying photos and their captions.
The Importance of Cam Degreeing
When a camshaft is “degreed” it means the camshaft position in the engine has been synchronized with the crankshaft position. Degreeing the cam is the only positive means to determine if the rise and fall of the pistons correctly matches the opening and closing of the valves. The truth is, several degrees of misalignment can have a profound effect upon engine operation.
In a perfect world, you’d only need to line up the timing marks on the timing gears (sprockets) and you’d be good to go. But the truth is, there’s a good chance dimensional stack ups will catch up to you. Things like tolerances in the camshaft, crankshaft, timing chain and sprockets can add up. As a result, checking the relation of the camshaft to the crank (or “degreeing the cam”) is the only option.