Serpentine belt size for VS and VT-VY Ecotec (edited)

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Serpentine belt size for VS and VT-VY Ecotec (edited)

Postby j_ds_au » Tue Jun 16, 2020 12:19 am

Hi,

According to Gates, the engine serpentine belt size for VS is 6PK2720, whereas for VT-VY, it's 6PK2830 (normally aspirated 3.8 litre V6 Commodore variants with A/C). So that's an increase of 110 mm in circumference.

Does anyone know why the increase in size? My VS has a modified VY Ecotec (some upper parts are apparently VS), and I need to figure out what size belt I should get for it.

(Although I could just get another the same as it's got now, I don't want to assume that's actually correct, given the incompetence of the Holden dealer that fitted it after they destroyed my original engine.)

Joe.
Last edited by j_ds_au on Thu Jun 18, 2020 9:12 pm, edited 2 times in total.

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Re: Serpentine belt size for VR-VS and VT-VY Ecotec

Postby delcowizzid » Tue Jun 16, 2020 12:24 am

Vn to vr all the same ecotec all the same
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Re: Serpentine belt size for VR-VS and VT-VY Ecotec

Postby j_ds_au » Tue Jun 16, 2020 2:28 am

delcowizzid wrote:Vn to vr all the same ecotec all the same

Oops! Yeah, VR is listed as 6PK2370, so that's smaller than the VS; i guess I just tend to consider the VR and VS as being very similar, I should have checked!

So then the question is, why did the belt size increase from VS to the latter Ecotec engines?

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Re: Serpentine belt size for VS and VT-VY Ecotec (edited)

Postby immortality » Tue Jun 16, 2020 9:17 am

What belt does it have now? Is the tensioner sitting in the correct travel range?

I think some of the pulley diameters might have changed? I had a VS before and the VX we have now certainly has a longer belt on it.

Did the AC pump change somewhere along the production life?

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Re: Serpentine belt size for VS and VT-VY Ecotec (edited)

Postby vlad01 » Tue Jun 16, 2020 9:05 pm

VS have different sized idler pulleys near the AC comp therefore needs a different belt.

Had this exact issue when replacing the pulleys on my nephews VS which we swapped out for a VX motor but wanted to reuse the VS belt, the bearings were stuffed in the VS ones so we got new VS idlers. The mechanic I got them from showed me both and stated the sizes were different.
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Re: Serpentine belt size for VS and VT-VY Ecotec (edited)

Postby j_ds_au » Wed Jun 17, 2020 12:38 am

Thanks, guys.

Now it's clear what I need to look for, so I should be able to check it out in the morning and figure out what belt to buy. :P

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Re: Serpentine belt size for VS and VT-VY Ecotec (edited)

Postby pman92 » Wed Jun 17, 2020 6:42 pm

I believe VS and early VT had the smaller belt. The change in idler pulleys was some time through VT. You can always swap to the other idler pulley size and use the matching belt. It's not all the pulleys that are different, I think only 1 of them is.
VS also has a different AC compressor, it's pulley size may be different, in which case there may be 3 belt sizes:
- VS
- early VT
- late VT to VY
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Re: Serpentine belt size for VS and VT-VY Ecotec (edited)

Postby j_ds_au » Wed Jun 17, 2020 8:49 pm

pman92 wrote:I believe VS and early VT had the smaller belt. The change in idler pulleys was some time through VT. You can always swap to the other idler pulley size and use the matching belt. It's not all the pulleys that are different, I think only 1 of them is.
VS also has a different AC compressor, it's pulley size may be different, in which case there may be 3 belt sizes:
- VS
- early VT
- late VT to VY

Thanks for those clues, they help sort out something that was confusing me. Looking at the Gates and Dayco information, the VS has the smaller belt, yet its ribbed idler pulley is larger than VT-VY, the opposite to what you'd expect! So it must be the AC compressor that's the main factor in the change of belt size.

Looking at my mostly-VY engine, its belt is currently the smaller VS one, but the tensioner mark says it's on the loose side by about 80% of a division. If this engine should actually take the larger VT-VY belt, then I can't imagine the smaller VS belt could stretch over time sufficiently to be on the loose side, it'd surely break first. So the AC compressor must be the original VS one and the "correct" belt must be the VS one.

The other finding this morning was that the ribbed idler pulley corresponds to the VT-VY size (76mm). Since a VS pulley would apparently be 90mm, this combination (VT-VY pulley and VS compressor) could account for why the tensioner mark shows the belt to be slightly loose (plus age, of course). The exactly correct belt size for my engine would then be one slightly smaller than the standard VS size.

So I'll be buying a 6PK2720, the VS size belt for my mostly-VY engine.

Joe.

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Re: Serpentine belt size for VS and VT-VY Ecotec (edited)

Postby j_ds_au » Tue Jul 07, 2020 12:35 am

Just a quick update ...

On the weekend I put in a new 6PK2720 belt, and now the tensioner indicator is pretty close to nominal, just a tad on the loose side of the centre mark. This is to be expected from a VS belt with a VS A/C compressor but a VY ribbed idler pulley (as this is a little smaller than a VS one).

Thanks for all your help figuring out the correct belt for my VY engine in my VS.

Joe.

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Re: Serpentine belt size for VS and VT-VY Ecotec (edited)

Postby The1 » Tue Jul 07, 2020 11:33 am

For the record i have a VT L67 in my VS with VS A/C, i fitted a 6PK2774. So your spot on depending on how good your tensioner is.

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