Timing Belt Streatch???

[Dougieb]

Hi,

As I was adjusting my valves (1972 Spider), I noticed that the timing belt has a good bit of play in it between the intake cam and the auxiliary shaft. If I poke it sideways with my finger the belt can "wiggle" back and forth about one inch. Not enough to touch the timing cover but enough to alarm me.

I am about to change it anyways, but:

is this a sign of stretching?
Is this normal?
Could it be that there was just a bit too much slack left in between those wheels? (bad install)



Thanks,
Dougieb

[azruss]

probably more a case of the belt not install correctly. the belt comes in contact with both sides of the aux pulley. If the slack wasnt removed from belt when installed, it would still be there. start by making sure the belt is properly nested in the crank pulley. pull tight on both sides to the aux pulley. hold the belt in that position so there is no slack between the crank pulley and the aux pulley on both side. continue ccw by wrapping the belt around the intake cam pulley. you may have to rotate the cam a half tooth to get it to pull tight. repeat the step between the intake and exhaust pulley. again, rotate the exhaust cam a half tooth to remove the slack. At this point, pull it over the tensioner bearing and release the tensioner spring.

[Dougieb]

Thanks, azruss.
That makes sense.
I will give that a go (with a new belt).
Will post what happens.

[Dougieb]

I am sure the timing belt is not properly installed.
Here is a photo of where the crank timing mark is when both the intake and exhaust cams are exactly at their correct marks.
I am guessing that the crank is one or two teeth off. (or both cams. depends on how you look at it.)



Just curious, any ideas on what this has done for the engine's performance?

Currently waiting for all of the parts to come in before I start taking things apart.
Will post update when finished.
Thanks again, AZRUSS.

[djape1977]

i've seen stretching timing belts, be aware that there are some cheap (chinese) copies out there. last year a friend of mine had a problem with "gates" timing belt. turned out it was made of plastic instead of rubber. went to gates homepage and found a big warning of illicit copyes and a manual how to recognize it.
re-set it and watch what happens over several weeks.

also had a customer come to mu shop with wrong timing, 2 teeth off on a crank. engine was working well, starting fine, running nice, revving up, just had no power, like it was running at 60-70hp at most and it was a 2 liter spider. after i re-set the timing it was smoking 205's in the back in 1st and second gear