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Thread: 4.2 Bell Housing Bolt Pattern

  1. #1
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    4.2 Bell Housing Bolt Pattern

    Since this site contains so many mechanically knowledgeable people I thought I would ask here.

    I was looking at a 4.2 installation into a Porsche Cayman tonight. The owner had a blown up mock up 4.2 out of a 2000 A8. Purchased a 2002 S6 4.2 for the real motor. The 2002 S6 bolted up to the trans were the 2000 was a different pattern all together. Only some holes matched up.

    Other than the RS6, I thought all other 4.2 (belt drive) were the same block, how far off am I ???


    With all the early Porsche watercooled M96 motors going south this is a great alternative that many owners are contemplating. Would suck to buy a motor only to find it does not fit up like the S6 motor did.

    Do I also understand that the V10 and W12 share the same bolt pattern as the RS6 ? Guess that means that Steve K's adapter will work with them.
    Rick

  2. #2
    Registered User hahnmgh63's Avatar
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    I think your right about the block, at least if they are 40v 4.2's. I've looked into a Cayman for an engine swap but why not go with a 3.8 or at least a 3.6 Porsche motor, that's what I'm doing, got the Cayman but the project is waiting until about 3 or 4 others get done. Also with the 4.2, you will have a custom wiring harness that may never talk to the gauges right, how are you going to do the tranny since the engine will be turned 180' around. Already 3.6 & 3.8 conversion out there so others have done much of the footwork.
    2003 White RS6 2013 Midnight Blue S5
    2013 Daytona RS5 2x944 Turbo's 1974 911 w/'91 3.6ltr motor
    Roy, WA

  3. #3
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    Hahnmgh63, I agree with the ease of poking a 6 back in but after looking at the 4.2 in there it is an easy fit. Some people view the cost of suitable replacement 6 too high. Guess it is the hotrodder project quest. The install is work but luckily we are in a part of the country where issues like wiring and cracking the ECU is not too big of a deal. Lots of car guys that work at Bosch and they are only a block away from my shop. Calibrators in Detroit are like Barista's in Seattle.

    For me, if I was going to do the swap I would go for a bigger bang for the effort and put a V10 or W12 in there, and I have plenty of big Porsche motors sitting around the shop.
    Rick

  4. #4
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    I knew that the D3 A8 4.2 block has the same P/n as the RS6 block, but never heard of the D2 A8 4.2 being any different than the C5 4.2 blocks. This is interesting...

    Do you know what transmission the A8 had in it? Could it have been an early 2000 production model with a 32V V8? I'm only guessing here.
    2012 Q7 TDI S-Line - 2010 GTI - 2007 A3 3.2 S-Line - 2003 RS6
    2001 Honda S2000 - 1977 Honda CBR 750-F2 - 1965 GMC 1500 WideSide

  5. #5
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    Steve, The S8 motor was a 40 valve. I broke a belt and and was replaced at my buddies shop with another motor. He had the blown motor in the back and offered it up as a mock up. Don't know the details from there. To everyone's surprise the permanent motor, the 2002 S6 bolted up better. I was not involved with the bolt up and don't have a mental picture from just looking at the S8 if it is the same as my RS6. Just was hoping someone with your comprehensive knowledge would blurt out the specifics.

    Next time I am over there I will take some detailed pictures to help with the identification process.

    Thanks,
    Rick

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