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Win Tools

3747-12 Dodge/Jeep 3.7 4.7 Valve Spring Compressor Like Miller 8387

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  • 3747-12 Dodge/Jeep 3.7 4.7 Valve Spring Compressor Like Miller 8387
  • Lower cost alternative to the 8426 and 8387
  • Equivalent to the Miller 8426 and 8387



The Win 3747-12 Valve Spring Compressor is used in place of the Miller 8426 or 8387 on Jeep, Dodge, Chrysler 3.7 and 4.7 engines. The original Mopar Miller numbers are 8426 and 8387. The Win brand is similar but stronger than the originals! The Miller numbers are listed repair manuals. The 3747-12 (like Miller 8426 and 8387). It's a specialty tool to compress the valve springs and access the keeper which is needed when changing the valve springs. Use of this tool is safely done without damage to the camshaft or camshaft lobes. There's a partial application below, however this tool works on 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012 and 2013. Refer to a service manual for detailed instructions on use. Also see the 3-in ONE Win 3747-123 that can be used for Rocker Arms as well as a Valve Spring Compressor. When the repair manual calls for an 8516A, 8387 or 8426 Miller tool, our 3747-123 is the best option. If you already have the 3747-12 the add-on 3747-3 can be purchased separately, which allows the tool to work as the 3-in ONE 3747-123 multi-purpose tool.

wise-auto-tools-canada.jpg Now also shipping to Canada. 

  • 2006 (DR, HB, KJ, ND, WK, XK) - Systems (9 - Engine, 3.7L, 9 - Engine, 4.7L)
  • 2007 (DR, HB, HG, KA, KJ, ND, WK, XK) - Systems (9 - Engine, 3.7L, 9 - Engine, 4.7L)
  • 2008 (DR, HB, HG, KA, KK, ND, WK, XK) - Systems (9 - Engine, 3.7L, 9 - Engine, 4.7L)
  • 2009 (DS, HB, HG, KA, KK, ND, WK, XK) - Systems (9 - Engine, 3.7L, 9 - Engine, 4.7L)
  • 2010 (DS, KA, KK, ND, WK, XK) - Systems (9 - Engine, 3.7L, 9 - Engine, 4.7L)
  • 2011 (DS, KA, KK, ND) - Systems (9 - Engine, 3.7L, 9 - Engine, 4.7L)
  • 2012 (DS, KK) - Systems (9 - Engine, 3.7L, 9 - Engine, 4.7L)
  • 2013 (DS) - Systems (9 - Engine, 4.7L)

Question - What's the difference between the Miller 8426, 8387 and the Win 3747-12, they look practically the same?

Answer - The Win 3747-12 is very similar to the 8426 and 8387 tools. Since it has a wider foot print it can be used in applications when the 8426 or the 8387 is called for. The Win Tool is stronger and works just like the Miller 8426 and 8387, at a lower cost. The 3747-123 has more function since it can be used to change broken valve springs or just to install replacement rockers or lifters. That's why many customers choose the Win 3747-123 because it can be used when a 8426, 8387 or 8516A is needed.

Question - Can I just use a "universal" valve spring compressor to do the same thing?

Answer - No. We have searched with all of our suppliers to find a universal type valve spring compressor and there's not one available that works for 3.7 and 4.7 Mopar engines. The best tool for doing rocker arm replacement, valve spring replacement, cam swaps etc is the Win 3747-123 that can be used when a Miller 8426, 8387 or 8516A is called for in a service manual. The Win 3747-123 offers a much lower cost alternative.


Question - Does this rocker arm remover work on Pentastar 3.6 engines?


Answer - No. There is not one made for the 3.6 Pentastar engine. The design does not allow. Shops typically purchase the Pentastar Combo kit, which includes timing chain holders, phaser locks and a crank holder, to save time from disassembling the front of the engine. See the product by clicking the following Pentastar Combo.


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4 Reviews

  • 5
    Saved the replacement of a head

    Posted by Jesse F on 18th May 2017

    Hello, First off the tool did the trick. However I would have designed a little different: instead of having to put the retainer/keeper in from the under the CAM (lots of prayer was going on when I was removing and installing the keepers) I would have made it to where the opening was from the top and not underneath. What an adventure.. I was on the side of a mountain hanging on by my fingertips it was so nerve racking (drop a keeper down in the engine and it's finished). This is the first time I have ever done this. But with the help of the Lord and this tool it's finished. Thank you Jesse

  • 5

    Posted by GEORGE W. on 3rd Feb 2017

    The tool worked good, I have no complaints.

  • 5
    Better than Miller

    Posted by Mike M on 8th Sep 2016

    Size of the piece that goes on top of the valve is same size as Miller but construction of main body is stronger. With a little practice works perfectly! Better price too!

  • 3
    Valve spring compressor tool

    Posted by Michael B on 7th Sep 2016

    It worked with a little help. What I see is the part that goes on top of the spring slides too far forward and makes it hard to get the retainer clips off.

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