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Hello All.
I just sucessfully finished my first timing belt change. I had 53k on the last belt and wanted to get it changed before it let me down. The engine is in a 1992 Z-34, coupled to a 5-Speed. My desire was to utilize the +6/-6 setup so I decided to make some tools to get the job done.
First off, I dont like the vague means of locating TDC provided by the factory. After turning up a TDC stop and using it with a 7" degree wheel, I found the factory mark to be around 2 degrees retarded.
Second, I wanted fixed hold down tools with the correct angles machined in them. Fortunately, I have an extra engine so I was able to take some measurements and engineer the tools prior to teardown.
With the tools I made, the timing process was easily done and it worked the first time. Boy, what a difference it made in drivability and performance! It isn't even the same engine. From the driver's seat, at idle, I can hardly tell that it's running. Power is greater and at a much broader rpm band. I must qualify that statement by saying that the engine never really ran right before. It was "rebuilt" when I purchased the car two years ago. The previously rough idle caused the manual transaxle to sound like a can of rocks. When I tore it down, I found pry marks on the cam carriers and the back side of the cam sprockets. The front exhaust cam was also retarded significantly. Necessarily, I don't think the "rebuilder" was able to remove the sprockets and get the cams timed right. I am indebted to a friend who loaned me his sprocket puller for the job.
I removed all four (lock ring type) cam sprockets with the engine in the vehicle. I would like to assert that the engine can not be timed properly without removing all four lock rings and allowing the belt to seat under proper tension before setting the timing. It has been suggested that the rear sprocket can be left on to circumvent the clearance issues encountered when trying to get it off. While it sounds like it should work, there is a fallacy in this theory since the belt tensioner is located in between the rear exhaust cam sprocket and the intermediate shaft sprocket. With the rear exhaust sprocket left on and the rear cams locked in position, slack in the new belt can only be reconciled by allowing the intermediate shaft to rotate forward, retarding the rear exhaust cam timing.
In all, it was a good experience, especially when I consider the money I saved doing it myself. Not to mention the strong possibility that a shop would have screwed it up anyway. I would like to thank this forum for all of the helpful information posted. I would especially like to thank Ben for his help / information. If any of you would like to see the tools I made, let me know and I will post some photos.
I just sucessfully finished my first timing belt change. I had 53k on the last belt and wanted to get it changed before it let me down. The engine is in a 1992 Z-34, coupled to a 5-Speed. My desire was to utilize the +6/-6 setup so I decided to make some tools to get the job done.
First off, I dont like the vague means of locating TDC provided by the factory. After turning up a TDC stop and using it with a 7" degree wheel, I found the factory mark to be around 2 degrees retarded.
Second, I wanted fixed hold down tools with the correct angles machined in them. Fortunately, I have an extra engine so I was able to take some measurements and engineer the tools prior to teardown.
With the tools I made, the timing process was easily done and it worked the first time. Boy, what a difference it made in drivability and performance! It isn't even the same engine. From the driver's seat, at idle, I can hardly tell that it's running. Power is greater and at a much broader rpm band. I must qualify that statement by saying that the engine never really ran right before. It was "rebuilt" when I purchased the car two years ago. The previously rough idle caused the manual transaxle to sound like a can of rocks. When I tore it down, I found pry marks on the cam carriers and the back side of the cam sprockets. The front exhaust cam was also retarded significantly. Necessarily, I don't think the "rebuilder" was able to remove the sprockets and get the cams timed right. I am indebted to a friend who loaned me his sprocket puller for the job.
I removed all four (lock ring type) cam sprockets with the engine in the vehicle. I would like to assert that the engine can not be timed properly without removing all four lock rings and allowing the belt to seat under proper tension before setting the timing. It has been suggested that the rear sprocket can be left on to circumvent the clearance issues encountered when trying to get it off. While it sounds like it should work, there is a fallacy in this theory since the belt tensioner is located in between the rear exhaust cam sprocket and the intermediate shaft sprocket. With the rear exhaust sprocket left on and the rear cams locked in position, slack in the new belt can only be reconciled by allowing the intermediate shaft to rotate forward, retarding the rear exhaust cam timing.
In all, it was a good experience, especially when I consider the money I saved doing it myself. Not to mention the strong possibility that a shop would have screwed it up anyway. I would like to thank this forum for all of the helpful information posted. I would especially like to thank Ben for his help / information. If any of you would like to see the tools I made, let me know and I will post some photos.
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