Acc. Serpentine Belt Tensioner Diameter?

Hey y'all, I'm changing the timing belt on my '03 4.7 and noticed the replacement accessory serpentine belt tensioner has a smaller pulley: 3.5" diameter on the new pulley, 4" on the old pulley. The timing belt was replaced by the PO so I don't know if the old tensioner is OE. I did notice the old serpentine belt didn't have a lot of clearance when removing it.

The new part is Dayco 89255.

What's the spec'd diameter for this pulley? Will it matter if I use the 3.5" pulley? I haven't installed it to check for fit but I'm guessing there's enough range in the tensioner to tighten the belt.

Thanks.

 

I mean, look at this purely from a mechanical perspective...

Notice the smaller pulley is offset, although it's at a weird angle so it's hard to see if what I'm thinking is correct. I assume they did that for a reason, i.e. using a smaller pulley, they needed to offset so it would engage the belt equally to a larger pulley.

Depending on how the belt contacts the pulley, if you measure from the center of the bolt hole to the edge of the pulley and it's roughly the same distance on both parts, as long as it's rolling while added expected tension, it shouldn't theoretically matter.

I'm talking about this measurement. Like, if the belt is only contacting on the surface between those bolt holes, and the pulley is offset in a way it'll hold the belt at tension that same distance away (the blue arrow width), I can't imagine it won't work fine. I'd personally prefer replacing with OEM either way.

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Hot damn, and there it is! Nice find. Yeah, as long as the engagement is at an equal point, that small of a diameter hop is no big deal. That pic shows it beautifully.

 

Bam! Solved. It does seem like it'll do what it's supposed to do. Thanks.