Hello,

I've searched and cannot seem to find the exact GM part number (Dayco OEM mfgr) for the 700sci Supercharger Belt Spring Tensioner. I see that Whipple sells one for $250.00 but since I need to paint it blue, I might as well just get 2 of the GM units and replace both at the same time, which will probably be the same cost as 1 of these from Whipple.

Does anyone know what the GM part number is of this part?

I would appreciate it.

Thank you!

Sure as heck looks like Dayco 89421. Compare with pic from Whipple, look for ore specs online. If it is, we can cross to AcDelco of course.
The pulleys won't match as the Merc assembly probably has a billet guided one made by Whipple.

Yes I agree. Dayco has several part numbers. I think the part numbers differ based on rotation and pulley that comes with it. But what I'm most concerned about is spacing/thickness of the tensioner and if they are different. I will be transferring the stock pulley over to the tensioner, but just wanted to double check if there is just one size tensioner or if there are different thicknesses? From what I can tell, all the HD tensioners look to be the same thickness, length, etc....just the pulley combo and spring direction/belt direction are different between them...

Okay , we can narrow it down, Can you take a pic of the other side of yours ? Ie: the side that mounts against the bracket. I can't find a photo of the Merc piece on this side. BTW, here is a huge listing with photos of any Dayco tensioners: https://www.rockauto.com/en/parts/da...ensioner,11659

Okay here are a few pictures of the tensioner and the pin guide location on the back. What I know is that it isn't a screw, rather a molded in pin like the "89421" above. After looking through a ton of pictures of the tensioners, I believe it is "89408" because of the location of the pin on the back. I've also attached a pic of the back of the bracket it bolts to which shows the location of the guide pin.

You can see that the tensioner spring is not straight up and down, rather twisted a little to the left. On the back, you can see the guidepin location in relation to the bent over spring.

The closest match I could find is the "89408" in terms of the look/shape of the tensioner and guide pin location.





[img]https://i.ebayimg.com/00/s/MjYxWDUwMA==/z/IywAAOSweWVXdoth/$_35.JPG?set_id=89040003C1

Actual part number from Dayco is 89415. Pin is in the proper location.

~ $105.00. Ouch! I bought a bunch a few years ago. Picked them up for about half that to replace originals and have spares.

Cleaned, sprayed with zinc chromate primer, painted with Merc color from the can.

UPDATE: Check find it parts. Selling for $89.19 each.

^^Could be !

89408- Pin is not in the proper location. Close though.

So, a Dayco 89415 ?
Here's one $45 from ebay.
https://www.ebay.com/itm/New-89415-D...-/162275283610