As the title says - head milled .010", thinner head gasket installed and i have slack in the timing belt. I 'fixed' the problem by tugging up on the tensioner while tightening the bolt on the tesnioner, like this:



Is there any longer tem (detrimental) effects to doing it this way? Mind you there's not much slack - but with the back timing belt cover off and the motor running, the belt looked like it was flopping around alot.

Thanks!

RJ

 

If the timing belt is too loose, it will have tendency to jump teeth. If the belt is loose, your ignition timing will also fluctuate, causing you to lose power. 3rd, when you mill the head in combination with a thin headgasket, your cam timing will be off, necessitating adjustable cam gears to get it right.

 

I know about the adverse cam timing effects. I have some extra gears, just need to do the math and offset their positioning (rather than buy adjustable units).

However i'd like the timing belt to be tight so it doesnt jump teeth, or worse, snap. The 'push on the tensioner' trick seemed to work - even helms says to apply pressure to the tensioner when tightening the bolt.

I'm just worried about any long term effects, and or a 'better' fix.

 

If there is still too much slack in the timing belt, you could elongate the hole in the tensioner bearing to give you more adjustment. I think the shop manual says you want about 2mm of belt deflection, but that's not how I tension timing belts. On customer cars, I loosen the tensioner, turn the crank counterclockwise until I feel stronger resistance due to compression, hold tension on the crank, and lock the tensioner down. The tensioner spring determines belt tension. Then I push down on the belt between the cam gears and eyeball it, experience tells me if the tension is right. On my own engines, I tighten the belt till it almost twangs like a guitar string. You can use the coat hangar trick, or pry with a screwdriver to obtain the desired tension, just remember to turn the crank counterclockwise to remove slack as you do it.

 

Thanks alot, i appreciate the tips. The head isnt crazy milled - but this was one issue i'm dealing with on this head swap (93 LS head/manifold on a 91 RS). Definately a learning experience.

 

Does thermal expansion come into consideration when tensioning the timing belt? I have a slight slack in my timing belt, but when you crank it counter clockwise, it becomes tight, is that how its supposed to be? Or is it suposed to be tight all the way?

 

You are looking for the total mount of slack in the belt. When you turn the crank, one side of the belt will get tighter, and slack will develope on the other side. The total deflection should be about 2.0 mm. Push down on the belt between the cam gears, apply a fairly large amount of pressure, that will take the slack out of both sides of the belt and the slack will be where you are checking it, between the cam gears.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by StinkyTofu &raquo;</TD></TR><TR><TD CLASS="quote">Does thermal expansion come into consideration when tensioning the timing belt? I have a slight slack in my timing belt, but when you crank it counter clockwise, it becomes tight, is that how its supposed to be? Or is it suposed to be tight all the way?</TD></TR></TABLE>
It probably makes the belt looser. Aluminum's CTE is large for a metal, but most polymers have much larger CTE. But I don't know what the fibers are made of in a timing belt...

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by b19coupe &raquo;</TD></TR><TR><TD CLASS="quote"> I loosen the tensioner, turn the crank counterclockwise until I feel stronger resistance due to compression, hold tension on the crank, and lock the tensioner down.</TD></TR></TABLE>

This is basicly how the service manual says to tension the belt. This is the best way I have found to tension the t-belt and it works every time.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Phat_Optimo &raquo;</TD></TR><TR><TD CLASS="quote">

This is basicly how the service manual says to tension the belt. This is the best way I have found to tension the t-belt and it works every time. </TD></TR></TABLE>

Thanks again guys

 

marco

 

homo, i mean polo...