# How much slack should timing belt have?



## noquacks (Jun 5, 2010)

people,

Shop manual says iuse a special "GM" tool to adjust timming belt on my 88 sunbird. Im kinda guessing here. Im putting back together my 'bird, and you tighten the belt by rocking the water pump back to tighten. BUT, if too tight, water pump can fain prematurely, they say. So how is one supposed to know just how much tension to apply?

(when I removed my old belt, I noticed it was sloppy- probably the cause of mmy idle running badly. Now, I dont want to tighten like a HE man).


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## titanoman (Nov 27, 2011)

There is a lash spec (1/2" of flex measured at a given point, for example).
Look in the specs section.
It would be silly to skip this very important adjustment.


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## ukrkoz (Dec 31, 2010)

eyeball tool says: if you twist belt by hand, so that back isde of it shows, it needs to be re- snugged or re-placed.


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## titanoman (Nov 27, 2011)

ukrkoz said:


> eyeball tool says: if you twist belt by hand, so that back isde of it shows, it needs to be re- snugged or re-placed.


Oh. The backyard mechanic way.


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## polarzak (Dec 1, 2008)

titanoman said:


> Oh. The backyard mechanic way.


Works for me.


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## noquacks (Jun 5, 2010)

Thanks, people. believe it or not, last night , in bed, relaxing, after a hard day, I opened up both Haynes comic book and official shop manual and the Haynes said "to tighten temporarily , then take it to the dealer for "proper" tightening....LOL!!

And the shop manual, was even worse- it said "tighten to specification", and they gave NO spec. Sheeesh. I looked high and low in the chapter, elsewhere, and no "specification". 

So, I am concerned with the bearings on thatwater pump, but I will take the advice yous offered. Titan, you say "lash spec of 1/2", but under how much force? The manual did say 1/4" movement at the middle of belt half way between cam sprocket and pump, but no force in lbs........


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## Double (Feb 15, 2012)

Can you lay a straight edge between the two sprockets and measure for 1/4" deflection?


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## Yoyizit (Jul 11, 2008)

Double said:


> Can you lay a straight edge between the two sprockets and measure for 1/4" deflection?


1/4" deflection over a certain distance and with some specified deflection force. A spring from a hardware store can be used to give it the correct force. One of these storm door snubber springs takes about 40 lbs to make it 1" shorter.


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## noquacks (Jun 5, 2010)

delayed thanks, guys. Got it done. Car runs great (still stumbling idle, though, tighten belt had no effect). No more oil leaks so far!!!


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## ukrkoz (Dec 31, 2010)

well, if y'all want to go that technical - buy a belt gauge. it's shown in any Haynes manual I have ever owned, and I owned many.


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## Hardway (Dec 28, 2011)

http://www.thecarconnection.com/news/1048058_gates-rubber-offers-free-belt-wear-gauge


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## silver_flash (Sep 28, 2012)

every time ive used a belt gauge to spec. it's way to tight. general rule of thumb is 3/4 " of play. so not from center with straight edge but if you can move it about 3/4" it's tight enough.


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## Hardway (Dec 28, 2011)

Flash, I have never used anything on a timing belt. The vehicles I have replaced timing belts have spring loaded idler pullys. :thumbsup:


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## silver_flash (Sep 28, 2012)

I replaced belts on a blower at work and used one of the belt gauges and tightened to what Manuel wanted. i should have used my better judgment and not tightened it down so far because it almost ruined the bearings. only had the motor turned on for 5 min.


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