What "degreeing a cam" means and why it matters

Degreeing a cam is the process of adjusting where your camshaft sits in relation to the crankshaft so that the valves open and close at the exact moment the engine needs them to. When you install a new camshaft, it does not always line up perfectly with the timing marks on your engine — even if you followed the instructions. A cam that is off by a few degrees will still run, but it will lose power, run rough at idle, or waste fuel.

The cam controls when the intake valves let the fuel-air mixture in and when the exhaust valves let the burned gases out. If the cam is retarded (installed too late), the valves open after the piston has already started moving, so you lose the full stroke. If the cam is advanced (installed too early), the valves open before the piston is ready, which can cause backfiring or poor idle quality. Degreeing the cam puts it in the sweet spot for your specific engine and driving style.

Key Takeaways

  • Degreeing a cam means rotating the camshaft slightly in its gear or sprocket to shift when the valves open and close, usually by a few degrees in either direction.
  • You will need a degree wheel (a large protractor that bolts to the crankshaft), a dial indicator, and a way to rotate the engine by hand — most people use a socket on the crankshaft bolt.
  • The process involves finding top dead center, setting the degree wheel to zero, then measuring how many degrees the intake valve lifts at specific points to compare against the cam's published specifications.
  • If the cam is off, you loosen the cam gear or sprocket bolts, rotate the cam slightly, and re-check until the valve lift matches the spec sheet within one degree.
  • This job takes two to four hours and requires patience and a clean workspace — metal shavings or dirt in the timing chain will cause problems later.

Tools and equipment you will need

A degree wheel is the centerpiece of this job. It is a large circular protractor (usually 8 to 10 inches across) that bolts to the front of your crankshaft. The wheel has degree markings around its edge, and a pointer bolted to the engine block points to the current degree as the crank rotates. Degree wheels cost $30 to $80 and are reusable across many engines.

You will also need a dial indicator (also called a dial gauge) mounted on a magnetic base or a clamp. The dial indicator measures how far the intake valve lifts as the cam rotates. A basic dial indicator costs $15 to $40. Mount it so the plunger rests on the intake valve rocker arm or lifter — it should move up and down as the valve opens and closes.

To rotate the engine, use a socket that fits your crankshaft bolt (usually 3/4 inch or 7/8 inch) and a breaker bar or ratchet. Do not use the starter motor — you need slow, controlled rotation. You will also need a wrench or socket set to loosen and tighten the cam gear or sprocket bolts, and a clean rag to wipe away any oil or debris.

Finding top dead center and setting up the degree wheel

Before you can measure anything, you must find top dead center (TDC) — the point where the number one piston is at the very top of its stroke. Remove the number one spark plug and install a piston stop tool (a bolt-like tool that screws into the spark plug hole) or use the old-fashioned method: insert a wooden dowel or plastic rod into the spark plug hole until it touches the piston, then rotate the engine slowly by hand until the dowel stops moving upward.

Once the piston is at the top, bolt the degree wheel to the front of the crankshaft. Rotate the wheel so that the zero-degree mark aligns with the pointer on the engine block. This is your reference point — from here, every rotation of the crank will show you exactly how many degrees have passed. Lock the wheel in place so it does not slip.

Now mount the dial indicator so its plunger rests on the intake valve rocker arm (or the lifter, depending on your engine type). Zero the dial indicator at this point. As you rotate the crank, the dial will show how far the valve has lifted. Write down the degree reading when the valve first starts to lift — this is your opening point.

Measuring valve lift and comparing to the cam specification

Slowly rotate the engine clockwise using the socket and breaker bar. Watch the dial indicator as it rises. The intake valve will lift, reach a peak, and then fall back down. Record the degree reading at which the valve begins to lift (usually 0.050 inch of lift is the standard "opening" point), the degree at which it reaches maximum lift, and the degree at which it closes (again, at 0.050 inch on the way down).

Compare these three numbers to the cam manufacturer's specification sheet. The spec sheet will say something like "intake opens at 12 degrees before top dead center, peaks at 45 degrees after top dead center, and closes at 78 degrees after top dead center." If your measurements are off by more than one degree, the cam needs to be adjusted.

If your opening point is later than the spec (the valve opens after it should), the cam is retarded and needs to be advanced — rotated forward in the gear. If the opening point is earlier than the spec, the cam is advanced and needs to be retarded — rotated backward. Most adjustments are only 2 to 4 degrees, so you are making very small movements.

Adjusting the cam and re-checking your work

To move the cam, you must loosen the bolts that hold the cam gear or sprocket to the camshaft. Do not remove them completely — just loosen them enough that the gear can rotate slightly on the shaft. On a gear-drive cam, you may need to loosen the cam gear bolt and the idler gear bolt. On a chain-drive or belt-drive cam, loosen only the cam sprocket bolts.

Rotate the cam gear or sprocket one tooth at a time in the direction you need. Each tooth on a typical cam gear represents about 4 degrees of crankshaft rotation (this varies by gear size, so check your engine manual). Make small adjustments — a quarter turn of the gear bolt is often enough. Tighten the bolts snugly but not fully, then rotate the engine by hand through a full cycle to make sure nothing binds.

Mount the dial indicator again and repeat the measurement process. Check the opening point, peak, and closing point against the spec sheet. If you are now within one degree, you are done. If not, loosen the bolts again and make another small adjustment. This process may take three or four tries — patience is more important than speed here.

Finishing the job and preventing timing drift

Once the cam is dialed in, fully tighten all the cam gear or sprocket bolts in a cross pattern (like tightening a wheel) so the load is even. Rotate the engine by hand through two full revolutions to confirm that nothing binds and the valves still open and close smoothly. If you feel resistance or hear a grinding sound, stop when ready and check for a bent pushrod or a valve hitting the piston.

Before you close up the engine, double-check that the timing chain or belt is tight and that the distributor (if your engine has one) is still pointing to the number one cylinder. A cam adjustment can shift the distributor timing, so you may need to rotate the distributor slightly to keep the spark in sync with the new valve timing.

Clean away any metal shavings or oil spills from the timing cover area. Reinstall the timing cover, spark plugs, and valve covers. Start the engine and listen for any rough idle, backfiring, or knocking. If the engine runs smoothly and idles cleanly, the cam is properly dialed in. If it still sounds off, the cam may need another small adjustment — do not ignore a rough idle, as it usually means the timing is still not quite right.

When to degree a cam and when to skip it

You should degree a cam if you are installing a performance or custom cam, if you are rebuilding an engine and want to restore it to original specs, or if you are chasing a rough idle or power loss after a cam installation. You should also degree a cam if you have removed and reinstalled the original cam — even if you marked the timing, small shifts can happen during removal.

You can skip degreeing if you are installing a stock replacement cam in a stock engine and the timing marks line up perfectly. Many stock cams are forgiving enough that being off by a degree or two will not cause noticeable problems. However, if you are installing an aftermarket cam or if the engine is already running rough, degreeing is worth the time investment.

Frequently Asked Questions

What if I do not have a degree wheel?

You can measure cam timing using the timing marks on the crankshaft pulley and a dial indicator, but it is less precise. Mark the pulley in 10-degree increments with a marker or tape, then use the dial indicator to find where the valve opens and closes at those marks. A degree wheel is cheap enough that it is worth buying if you plan to do this more than once.

Can I degree a cam without removing the timing cover?

No. You need to see the cam gear or sprocket and be able to loosen its bolts. You also need to bolt the degree wheel to the crankshaft, which requires access to the front of the engine. The timing cover must come off.

What if the cam is off by more than 4 degrees?

If the cam is off by more than 4 degrees, check that you installed it correctly in the first place. Make sure the timing chain or belt is not skipped a tooth, and verify that the crankshaft and camshaft gears are meshing properly. If everything looks right, the cam may have been ground incorrectly by the manufacturer — contact them before making large adjustments.

Does degreeing a cam change the horsepower?

Degreeing a cam to match its specification will restore the power and efficiency the cam was designed to deliver. If the cam was installed retarded, degreeing it will improve throttle response and low-end torque. If it was advanced, degreeing it will clean up the idle and reduce backfiring. The change is usually noticeable but not dramatic — a few horsepower and better drivability.

What happens if I get the direction wrong and advance the cam when I should retard it?

The engine will run worse — rougher idle, more backfiring, or loss of power. You will catch this when ready when you start the engine. Stop, loosen the cam bolts, rotate the cam in the opposite direction, and re-check. There is no damage from going the wrong way; you just have to redo the adjustment.