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Timing belt

I need information for timing the camshafts on a 1998 Contour, four cylinder, dual cam, Zetek, CTV engine. Specifically the exhaust cam. What is the purpose of varying the timing on the exhaust cam? Is it advancing or retarding the cam in relation to the crank? Thanks in advance for any information - Stan

If you look at the back end of the camshafts, each has half of it cut out to create flats. A special tool is inserted under the camshafts and on top of the head. This special tool is just a flat steel bar of the proper thickness. Once this bar is inserted to prevent the camshafts from rotating, the timing belt can be installed.


I aligned the shafts with the crank as per instructions from dealer (computer printouts.) Crankshaft #1 TDC, tool inserted in camshafts, correct tension set on tensioner. My problem is that when I remove the tool holding the camshafts and rotate the crankshaft the two turns & back to TDC, as instructed to check cams are still aligned, the Exhaust cam is lagging the crankshaft. While turning the crankshaft the spring in the camshaft sprocket compresses until it gets tight enough to overcome the valve springs then the cam snaps forward. In other words the exhaust cam does not turn exactly with the crank. Therefore when I get back to TDC after two turns the exhaust cam is not in the correct position. The intake cam is aligned correctly. I realize this is an interference engine so I don’t want to get it wrong. thanks Stan

Most dual-cam engines I’ve dealt with have a method to relate the two cams together on the belt, along with a method to lock them in place. On a Volvo S70, it had grooves on the back end of the shafts to align them to TDC, similar to your Contour. To keep the sprockets aligned to each other on the belt, the sprocket bolt holes were slotted to allow for infinite adjustment. With the the belt on and tensioned and crank set at TDC, the sprocket bolts are loosened, and the alignment bar is set in place to line the camshafts to TDC. Then, the sprocket bolts are tightened to spec to keep everything in line.

I prefer the methos Toyota used with the Supra. My Toyota Supra uses dowel pins between the cam sprocket and the cam shaft. There are 5 pin locations on each to help keep the two gears timed together. You install the belt, tension it in place and rotate the crank two rotations to lock in the tension. At TDC, you see how far each cam is off. Remove the belt, adjust the dowel to another pin position, each one adjusting 1 to 2 degrees per location. Reinstall belt, and repeat until the cams stay lined up with the crank at TDC.