Problem getting crank and cam timed
Problem getting crank and cam timed
I'm located in Victoria BC, and I'm trying to get my rebuilt L-20B engine crank and cam timed properly. I've got two manuals but I can't seem to make it work. I'm stalled until I can solve this problem. Is there anyone out there who can help? Thanks.
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datzenmike
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- Posts: 6081
- Joined: 24 May 2006 12:40
- Location: Van. Isle.
Re: Problem getting crank and cam timed
It's easy, here's what to do.
If the engine is assembled or in the car:
SET CRANK TDC
Place a ratchet extension through one of the cam sprocket holes to keep it from turning, and and loosen the sprocket retaining bolt. This will make it easier to remove later, without the risk of bumping the motor off TDC once it is set. Disconnect the coil wire from the distributor cap and remove the #1 spark plug and place thumb over the hole. Have someone bump the starter to jar the engine ahead a quarter turn at a time. When air pushes out past your thumb, the piston is coming up on the compression stroke. Stop. This places the motor close to the TDC Compression. Now find the saw toothed timing marker bolted to the front of the timing cover, (L20Bs are usually near the 10 o'clock position below the fuel pump)and are marked 20/10/0. Look on the rear-most rim of the back pulley on the crank. Within a few inches of the timing mark there should be a small notch cut in it. The engine can most easily be jogged into position using a 24mm socket and bar. Align the notch on the rim, with the zero (0)on the timing plate. You are now at TDC Compression on the crank. Engine must not be turned from this point on.
SET CAM
Remove valve cover and lock the timing chain with a wedge of wood between chain guides, to prevent the tensioner from falling out. Observe that the cam sprocket has three numbers on the outer rim just below the chain. For a starting point the #2 number should be in the 12 o'clock position. Remove the previously loosened cam sprocket bolt and fuel pump eccentric, and remove and position the sprocket on the chain so that the #2 is exactly in the 12 o'clock position. To install the sprocket, you may have to rotate the cam till it's dowel fits into the back of it. Finger tighten the retaining bolt. On the sprocket, below the #2 there is a finger sized hole. Using a flashlight, look through this hole and down at the back of the sprocket where you will see a small V cut in it. Just above this V there will be a small horizontal line etched into the cam thrust plate. This line should be just to the left of the V. If it is not, this means that the timing chain has stretched. To adjust for chain stretch, remove the sprocket and rotate 90 degrees clockwise and install with the #3 in the 12 o'clock position and check the position of the etch mark. Each number is a 4 degree change in cam timing. It should now be just to the left of the V notch. If it is still not in the proper position the chain will need replacing. If it now IS in position, re-install the fuel pump eccentric and just snug the retaining bolt. Remove the timing chain lock and finish tightening the cam sprocket retaining bolt. Cam is timed to the crank.
If the engine is assembled or in the car:
SET CRANK TDC
Place a ratchet extension through one of the cam sprocket holes to keep it from turning, and and loosen the sprocket retaining bolt. This will make it easier to remove later, without the risk of bumping the motor off TDC once it is set. Disconnect the coil wire from the distributor cap and remove the #1 spark plug and place thumb over the hole. Have someone bump the starter to jar the engine ahead a quarter turn at a time. When air pushes out past your thumb, the piston is coming up on the compression stroke. Stop. This places the motor close to the TDC Compression. Now find the saw toothed timing marker bolted to the front of the timing cover, (L20Bs are usually near the 10 o'clock position below the fuel pump)and are marked 20/10/0. Look on the rear-most rim of the back pulley on the crank. Within a few inches of the timing mark there should be a small notch cut in it. The engine can most easily be jogged into position using a 24mm socket and bar. Align the notch on the rim, with the zero (0)on the timing plate. You are now at TDC Compression on the crank. Engine must not be turned from this point on.
SET CAM
Remove valve cover and lock the timing chain with a wedge of wood between chain guides, to prevent the tensioner from falling out. Observe that the cam sprocket has three numbers on the outer rim just below the chain. For a starting point the #2 number should be in the 12 o'clock position. Remove the previously loosened cam sprocket bolt and fuel pump eccentric, and remove and position the sprocket on the chain so that the #2 is exactly in the 12 o'clock position. To install the sprocket, you may have to rotate the cam till it's dowel fits into the back of it. Finger tighten the retaining bolt. On the sprocket, below the #2 there is a finger sized hole. Using a flashlight, look through this hole and down at the back of the sprocket where you will see a small V cut in it. Just above this V there will be a small horizontal line etched into the cam thrust plate. This line should be just to the left of the V. If it is not, this means that the timing chain has stretched. To adjust for chain stretch, remove the sprocket and rotate 90 degrees clockwise and install with the #3 in the 12 o'clock position and check the position of the etch mark. Each number is a 4 degree change in cam timing. It should now be just to the left of the V notch. If it is still not in the proper position the chain will need replacing. If it now IS in position, re-install the fuel pump eccentric and just snug the retaining bolt. Remove the timing chain lock and finish tightening the cam sprocket retaining bolt. Cam is timed to the crank.
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