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how to determine custom belt length? 

 

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 Post subject: how to determine custom belt length?
Posted: Mon Oct 20, 2008 8:39 pm 
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My car is almost ready to go but i need to work out a custom belt length. This is because my engine accessories are all AU except for an EF/EL/XH a/c pump.

I've tried the EF/EL and AU belts, but they are quite a bit too long. The EF/EL pump is mounted higher, which means a shorter belt is needed. The belt needs to be 260mm plus an amount for tensioning shorter than the AU belt.

I have measured with some thin rope the length where the belt runs with the tensioner pulley fully extended, this is 2100mm, so an amount would need to be taken off that so that tension can be developed. But now i'm wondering whether that rope was too stretchy.

Based on the AU minus 260mm & tensioning data Repco said there is a 6PK2120, and based on the thin rope data they said there is a 6PK2080, 6PK2070, and a 6PK2055, but there may be more sizes in between. I haven't actually fitted a serpentine before so i could only take a hunch as to how much extra to take out for the tensioning.

Help appreciated.

 

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Posted: Mon Oct 20, 2008 10:03 pm 
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use brickies string... it will give you a more accurate indication
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Posted: Mon Oct 20, 2008 10:21 pm 
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66 coupe wrote:
use brickies string... it will give you a more accurate indication

I think i'll recheck my measurements, but the AU measurements are accurate. I just need to measure the AU's overall length and subtract the 260mm and an extra bit for tensioning to get a desired custom length.

How much should i take off for the tensioning?

[PS - from working in the past as a brickies labourer, brickies use stretchy line. Some line is stretchy and some is not]

 

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Posted: Mon Oct 20, 2008 10:24 pm 
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When you say fully extended you mean tension released?
If so, a belt any shorter then 2100 isn't going to fit, there would be no slack at all to get it on the pulleys.
Take a measurement with the tensioner 'fully tensioned' and one with it fully released, and go for a belt length in between?

 

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Posted: Mon Oct 20, 2008 11:08 pm 
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Steady ED wrote:
When you say fully extended you mean tension released?
If so, a belt any shorter then 2100 isn't going to fit, there would be no slack at all to get it on the pulleys.

The tensioner is at the position it assumes when there is no belt fitted. So if you fitted a belt that was a neat fit to that, you couldn't tension it.

Quote:
Take a measurement with the tensioner 'fully tensioned' and one with it fully released, and go for a belt length in between?

That sounds logical. The problem there is that i only have 1/4 and 1/2" drives. I was thinking that i would have to use a lever against the underside of the pulley mount and the belt where it wraps over the pulley.

Or maybe i should go to the effort of grinding a large bolt square, and turn it via twin nuts locked-off against each other?

There seems to be a lot of tension in the tensioner.

 

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Posted: Tue Oct 21, 2008 1:22 am 
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or goto s**t and get a $5 3/8th's bar. There is a decent amount of tension on there yes.

I haven't tried, but I would imagine you should be able to wedge a block of wood or something between the crank pulley and the tensioner to push it out.

 

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Posted: Tue Oct 21, 2008 3:40 am 
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yeah I'd just get a 3/8"s breaker.
You're going to need something eventually to get the belt on anyway :)

 

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Posted: Tue Oct 21, 2008 1:32 pm 
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A bit of grinding of a 1/2" bolt shaft made a good 3/8' tensioner device.

Now i see another problem, the tensioner actually loosens the belt. I figure this is because the AU a/c pump mounts significantly lower and closer to the engine than the EF/EL pump, changing the geometry and the effect of the tensioner. I thought this combination had been done before? I can't think of a solution to this right now.

I compared my EL tensioner to my AU one and they are identical. Since the EL tensioner must work with the EL a/c pump, and the harmonic balancer is in the same position on both motors, i can only think the timing case cover bolt holes for the tensioners are different between the EL and AU (actually i can check this because i have an EL timing case cover in the XG).

Can someone please confirm information i have received that the EF, EL and XH pumps are the same, that they all have one bolt through the top and two through the bottom?

[I have read here that the XH upper pulley on the tensioner is at a different angle, could this mean something to my scenario?].

Now i wonder if i should have instead ground the AU a/c bracket back for dizzy clearance, used an AU pump, and got the a/c pipes professionally sorted.

Help wanted please.

 

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Last edited by relaxed_diplomacy on Tue Oct 21, 2008 1:42 pm, edited 1 time in total.

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Posted: Tue Oct 21, 2008 1:36 pm 
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Gaz wrote:
or goto s**t and get a $5 3/8th's bar.

Thanks for the suggestion, but unfortunately the nearest supercheap is 2 3/4 hours drive away.

 

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Posted: Tue Oct 21, 2008 4:02 pm 
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I just refitted the EL a/c pump using the EB a/c bracket, which sees the pump mounted lower. Even so, the tensioner only tensioned for the first say 4mm of it's travel, then the belt got slacker the more it was supposed to tension things.

I checked the tensioner mounting bolt holes on my EL motor and they look the same as those on my AU motor. So i am really at a loss as to why the tensioner is not working, . . . except of course that the angle of the tensioner's lever sees the pulley travel downwards during it's arc, which sees the belt slacken.

I looked to see if there is another way to mount the tensioner, but there is not.

??

 

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Posted: Tue Oct 21, 2008 4:31 pm 
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When i had another look at the AU a/c mounting bracket it looke like the pump would be mounted in a similar position to that on an EL. So i'm darned if i can work out why i have 260mm+ spare belt and the tensioner doesn't tension. For the sake of it i have tried to mount the belt different ways, but only one other way was possible and it was not at all sensible.

??

 

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Posted: Tue Oct 21, 2008 4:39 pm 
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PROBLEM SOLVED!

Thankfully almost everyone around here own's falcons and just a few metres away was a friend's AU, and how about that, the belt goes around in a way i just didn't think of. The way i was doing it seem logical, believe me, it looked more right that the way they are suposed to go.

 

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Posted: Wed Oct 22, 2008 1:02 am 
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was about to suggest the belt might have bee routed wrong :P Good to see you sorted it.

 

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