Do timing belts shrink?!

[bgd73]

Hey,

Do timing belts shrink? I am getting an after ignition sound out the valve side on driver cyl head that goes away after 1500rpm or so. If letting exhaust out too soon, (and running good otherwise) wouldn't the belt have to shrink?:-\

[Subarian]

I've never heard of one shrinking. They're specifically designed to avoid stretching, but I would think that same design would preclude shrinking.

[northguy]

Maybe a bearing is going out.

[Roundeye]

Perhaps you are hearing an exhaust leak or bad lifter? Describe more this "after ignition sound"....

 

As mentioned, timing belts do not shrink. They turn into chewing gum when contaminated with coolant and oil. They can wear out and something to consider.......can be installed improperly. Getting one a tooth off will cause it to run rough. This will seem to smooth out as engine speed increases, but will still lack power. Any skipping or loping will be more pronounced at idle.

[bgd73]

Perhaps I'm a crackhead

It is stretching, triggering the tensioner to move up. It is the oil pump timing belt (the only one I have ever broken). I guess it is time to give it new tensioners etc. The exhaust has been reworked 3 times by a bad welder before done correctly within a few days. That is how I know there is no leaks (I got underneath it to verify). At a smoother rpm the belt eases off tensioner, taking noise away....It also explains the hard time keeping exhaust together.The exhaust valve time is affected. I seemed to have gone industrial strength on the ol' soob's exhaust!