Turning the engine backwards.... what happens?

[Robotech]

I've been told that you can't turn the engine backwards. I changed out the lifters and turned the engine backwards when one of my paper towels got stuck under some teeth in one of the cam sprockets. It only went backwards maybe 6 inches. I assume that its fine, however, the timing belt between the exhaust/intake sprockets was a little loose now it is night and tight. I assume the tension got taken up somewhere?

I was told by a guy that you don't run it backwards because it will make the tensioner take up the slack somehow. Other people have mentioned that it would cause the belt to jump teeth. I don't believe that it jumped teeth for me, but the tension on the belt seems to have changed at least between the sprockets. I'm trying to understand the physics of what happens when you run this backwards if someone would be so kind as to explain it to me.
Thank you kindly
David

 

[DSM1G90]

Been there and done that and I'm still on the road after a belt change..and that was six years and 31k miles ago. You rotate the travel backwards, the tensioner will not keep the belt tight and the belt can easily hop a tooth or two since the long (pull) side of the belt will lose tension.

Just double check everything.


-DSM

 

[tmoney20g]

Its not like you turned it backwards at 900 rpm, you turned it at like 1 rpm, it's nothing to worry about.

 

[Robotech]

I've turned the engine by hand about 10 times and there was no binding (valve hitting the cyclinders). So I wasn't too worried, but thank you for reassuring me.

 

[1990TSIAWDTALON]

I have had the other experience where the timing belt jumped a couple cogs because of lack of tension on it. Maybe it was a fluke or maybe some others got lucky or maybe my tensioner just wasn't doing its job anymore, but it did happen to me so I had to retime the thing. Lucky I noticed it tho. Just MTC.

 

[Robotech]

I have had the other experience where the timing belt jumped a couple cogs because of lack of tension on it. Maybe it was a fluke or maybe some others got lucky or maybe my tensioner just wasn't doing its job anymore, but it did happen to me so I had to retime the thing. Lucky I noticed it tho. Just MTC.

How did you notice that the timing had changed?

 

[dsmcrzy]

Rotate the engine the correct way and line up all the timing marks. If it didn't jump them cams should line up when the crank is lined up. You may have to rotate the crank 2 times. 2 crank revolutions = 1 cam gear revolution.