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Thread: Let The M73 Swap Begin!

  1. #26
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    I would suggest changing cam seals and front/ rear crank seals while you have it on a stand.

  2. #27
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    Don't touch the headgaskets unless they NEED replacing. Personally, I would put in new valve stem seals (this is really easy in an engine-out situation). Another one would be the rear main seal, as well as upper and lower oil pan gaskets. Cam chain tensioner o-rings are also a good candidate. I would also time the cams. Distributor base seals and water pipe o-rings. Do not mess with the valley cover gasket unless it is currently leaking - those mounting studs snap fairly easily. Other than that, just take a good look at everything as you go along.
    '93 850Ci - Mineralweiß Metallic

    2001 740iL - Titansilber
    ALPINA B7 -Alpinweiß III


    ...the price of cool ain't cheap!

  3. #28
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    Del Mar, CA
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    91 850i, 01 740i, 06 760
    I have replaced the valley pan on 2 91 motors and broke 1 bolt on the first and 3 on the 2nd. In all cases the bolts broke close to the head and left plenty of exposed shank after removing the cover. With a bit of work I was able to unscrew them all. It is a lot easier to deal with a broken bolt with the engine on a stand as opposed to leaning over a fender. Despite the warnings I would do it now to avoid having to deal with it later. Also the cover at the rear of the block. The problem with all of these is coolant seeps into the bolt threads and corodes them. I think the later engines used better quality (galvanized) bolts and are less prone to corosian.

  4. #29
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    1998 BMW 750iL
    I think replacing the spark plugs as part of the preventative maintenance is a good idea. Replacing them while the engine is in is a headache, especially when you get to the last 4 spark plugs. I went with NGK on mine due to reviews from other m73 owners and their preference over Bosch.

  5. #30
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    '90 850iM70B54, '91 850i
    Quote Originally Posted by dragon850 View Post
    M73 direct transplant with proper tuning is the way to go. dont mess around with M70 heads.
    mess around? There is no mess with using M70 heads. And I quite honestly see no advantage in using the M73 heads but am happy to learn.
    A pure M73 swap is certainly easier (except the exhaust issue) and I've done it a few times as well. Performance wise the M70B54S is way ahead though.
    You basically get CSi performance versus standard M73 performance. And the cost of the Schrick cams versus custom made downpipes is IMO not a reason to say NO.
    If someone has a budget that tight i recommend to stay away from such a project in the 1st place.



  6. #31
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    Quote Originally Posted by TxGR8White View Post
    The slight gain in HP using the M70/Schrick combo, is not worth the extra work in my book. Also, the camshaft oiling spraybar on the M73 is 1000x better, and let's not forget the M73 has roller rockers. I agree with you, change out the front lower timing cover and just drop that baby in. You will be just as happy(especially with the 3.91),with a lot less work. I do the same thing: when I want a kick in the pants, I climb into the cockpit of the B7.
    375HP versus 326HP is just a slight gain in your opinion? OK, maybe a personal thing. And what's so great about the roller rockers? I've seen broke ones but never saw a really broke rocker in a M70 head - only worn ones.
    And the oil feed pipe in the M70 heads are absolutely OK as long as the banjo bolts are in place. What it comes down to IMO is saving the job of replacing heads with all related work, time and expenses versus getting 50 extra ponies.

    - - - Updated - - -

    Quote Originally Posted by TxGR8White View Post
    Don't touch the headgaskets unless they NEED replacing. Personally, I would put in new valve stem seals (this is really easy in an engine-out situation). Another one would be the rear main seal, as well as upper and lower oil pan gaskets. Cam chain tensioner o-rings are also a good candidate. I would also time the cams. Distributor base seals and water pipe o-rings. Do not mess with the valley cover gasket unless it is currently leaking - those mounting studs snap fairly easily. Other than that, just take a good look at everything as you go along.
    100% agreed. Exactly what I'd recommend as well.



  7. #32
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    Jul 2014
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    '91 e31 M70

    Let The M73 Swap Begin!

    Well, I’m at work and don’t get to actually open it up and start playing, but this just arrived today. Poor guy, we have a very steep driveway and this thing weighs 452 lbs!!



    Well, unwrapping it was as far as I got before the wife called me in for dinner and family time...



    Sent from my iPhone using Tapatalk
    Last edited by adwebinc; 12-20-2017 at 09:19 PM.
    '07 e65|N62 - Alpina B7 - Black Sapphire|Black|Loaded|GONE
    '02 e46|M54 - Orient Blue|Beige|'Vert|GONE
    '00 e39|M52 - Anthrazit Metallic|Grey|GONE
    '01 e38|M73 - Anthrazit Metallic|Schwarz|Shadow-Line|GONE
    '91 e31|M70 - Schwarz|Schwarz|M70|FOR SALE

    '13 328i Auto - Black Sapphire|Coral Red|Sport Line|GONE
    '05 545i SMG - Jet Black|Black|Bamboo Anthracite|GONE
    '07 335i Auto - Montego Blue|Grey|GONE
    '05 545i SMG - (Euro Delivery 7/22/05)|Black Sapphire|Auburn|GONE
    '97 528i Auto - GONE

  8. #33
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    We are also about to start this project, I will use this thread if you don't mind adwebinc to post pics and share info and progress.

  9. #34
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    Quote Originally Posted by dragon850 View Post
    We are also about to start this project, I will use this thread if you don't mind adwebinc to post pics and share info and progress.
    That’s what this forum is all about... collaboration!! Let’s share best practices, struggles, etc.

    My gasket kit is on its way as well. Should be here this week.


    Sent from my iPhone using Tapatalk
    '07 e65|N62 - Alpina B7 - Black Sapphire|Black|Loaded|GONE
    '02 e46|M54 - Orient Blue|Beige|'Vert|GONE
    '00 e39|M52 - Anthrazit Metallic|Grey|GONE
    '01 e38|M73 - Anthrazit Metallic|Schwarz|Shadow-Line|GONE
    '91 e31|M70 - Schwarz|Schwarz|M70|FOR SALE

    '13 328i Auto - Black Sapphire|Coral Red|Sport Line|GONE
    '05 545i SMG - Jet Black|Black|Bamboo Anthracite|GONE
    '07 335i Auto - Montego Blue|Grey|GONE
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  10. #35
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    You two must have invested in "Bitcoin" early!
    1993 850Ci.....18 years & 165,000 miles and counting!

  11. #36
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    Let The M73 Swap Begin!

    Quote Originally Posted by TedBobo View Post
    You two must have invested in "Bitcoin" early!
    Haha... unfortunately no... but, this is my “golf” habit and it keeps me out of trouble. And it’s actually cheaper than golf. And usually less aggravating... usually.


    Sent from my iPhone using Tapatalk
    '07 e65|N62 - Alpina B7 - Black Sapphire|Black|Loaded|GONE
    '02 e46|M54 - Orient Blue|Beige|'Vert|GONE
    '00 e39|M52 - Anthrazit Metallic|Grey|GONE
    '01 e38|M73 - Anthrazit Metallic|Schwarz|Shadow-Line|GONE
    '91 e31|M70 - Schwarz|Schwarz|M70|FOR SALE

    '13 328i Auto - Black Sapphire|Coral Red|Sport Line|GONE
    '05 545i SMG - Jet Black|Black|Bamboo Anthracite|GONE
    '07 335i Auto - Montego Blue|Grey|GONE
    '05 545i SMG - (Euro Delivery 7/22/05)|Black Sapphire|Auburn|GONE
    '97 528i Auto - GONE

  12. #37
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    Quote Originally Posted by wokke View Post
    375HP versus 326HP is just a slight gain in your opinion? ...
    Well, I consider a substantial gain to be 100+HP. I am also looking at it from the standpoint that SCHRICK Cams are around $2500 the last time I looked, and for that kind of money, I can do without the extra 50 ponies (not to mention the extra work - I'm getting old....)
    '93 850Ci - Mineralweiß Metallic

    2001 740iL - Titansilber
    ALPINA B7 -Alpinweiß III


    ...the price of cool ain't cheap!

  13. #38
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    Who said m73 will only produce 326HP???
    Guys in Poland are putting out over 360 hp with live tuning...

  14. #39
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    Congrats Bro.

    I’m excited to see your progress and lending a hand next time I’m in town.


    Sent from my iPhone using Tapatalk

  15. #40
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    My 250,000 mile M70 had cam lobes that were just as shiny and just as smooth - the whole point of a roller rocker is to reduce the friction/drag of the arm on the cam - BMW even calls them "drag links"...
    '93 850Ci - Mineralweiß Metallic

    2001 740iL - Titansilber
    ALPINA B7 -Alpinweiß III


    ...the price of cool ain't cheap!

  16. #41
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    Quote Originally Posted by t8303at View Post
    Congrats Bro.

    I’m excited to see your progress and lending a hand next time I’m in town.


    Sent from my iPhone using Tapatalk
    I need all the help I can get, so come on down!!

    Santa came a little early and brought me this fun stuff:

    Not specifically related to the engine swap, but I am going Steffan’s route with my back boxes:



    And goodies for the engine swap. I found a set of NOS cams for a very reasonable price from a forum member. So, that complicated things on my decision. I’m very keen to understand the tune possibilities for the M73 heads. If I can get to the same place with the stock heads and a tune, then I’ll go that route.

    I do plan to perform a leak down test to see what I’m working with. That may help dictate which way to go.






    Sent from my iPhone using Tapatalk
    '07 e65|N62 - Alpina B7 - Black Sapphire|Black|Loaded|GONE
    '02 e46|M54 - Orient Blue|Beige|'Vert|GONE
    '00 e39|M52 - Anthrazit Metallic|Grey|GONE
    '01 e38|M73 - Anthrazit Metallic|Schwarz|Shadow-Line|GONE
    '91 e31|M70 - Schwarz|Schwarz|M70|FOR SALE

    '13 328i Auto - Black Sapphire|Coral Red|Sport Line|GONE
    '05 545i SMG - Jet Black|Black|Bamboo Anthracite|GONE
    '07 335i Auto - Montego Blue|Grey|GONE
    '05 545i SMG - (Euro Delivery 7/22/05)|Black Sapphire|Auburn|GONE
    '97 528i Auto - GONE

  17. #42
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    Please give Santa my address! I've been good all year.
    1993 850Ci.....18 years & 165,000 miles and counting!

  18. #43
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    Quote Originally Posted by TedBobo View Post
    Please give Santa my address! I've been good all year.



    Sent from my iPhone using Tapatalk
    '07 e65|N62 - Alpina B7 - Black Sapphire|Black|Loaded|GONE
    '02 e46|M54 - Orient Blue|Beige|'Vert|GONE
    '00 e39|M52 - Anthrazit Metallic|Grey|GONE
    '01 e38|M73 - Anthrazit Metallic|Schwarz|Shadow-Line|GONE
    '91 e31|M70 - Schwarz|Schwarz|M70|FOR SALE

    '13 328i Auto - Black Sapphire|Coral Red|Sport Line|GONE
    '05 545i SMG - Jet Black|Black|Bamboo Anthracite|GONE
    '07 335i Auto - Montego Blue|Grey|GONE
    '05 545i SMG - (Euro Delivery 7/22/05)|Black Sapphire|Auburn|GONE
    '97 528i Auto - GONE

  19. #44
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    Quote Originally Posted by TedBobo View Post
    Please give Santa my address! I've been good all year.
    If that were true, Santa would already know.
    Desecrator of all things Sacred

  20. #45
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    Progress so far, sick M70 engine removed, M73 partially disassembled.



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    Last edited by dragon850; 12-29-2017 at 11:17 AM.

  21. #46
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    But my local BMW dealership has clean floors.

  22. #47
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    dragon850 is this a thread jack? I thought you were on the west coast, and the OP is here in the midwest. Which car are we working on now?
    Desecrator of all things Sacred

  23. #48
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    Quote Originally Posted by 72tpik5 View Post
    dragon850 is this a thread jack? I thought you were on the west coast, and the OP is here in the midwest. Which car are we working on now?
    No we are sharing a thread and info on what needs to be done to swap in m73.

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  24. #49
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    Excellent! That is a brilliant idea.
    Desecrator of all things Sacred

  25. #50
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    Let The M73 Swap Begin!

    Quote Originally Posted by dragon850 View Post
    No we are sharing a thread and info on what needs to be done to swap in m73.

    Sent from my SM-G925T using Tapatalk
    And you have already jumped way out in front! Hoping to make some progress this weekend.

    Still really need to decide on which way to go with the heads. @dragon850 - do you have any performance numbers on the tune for the M73 heads? I now have a set of M70 heads and Schrick cams in my garage along with the full M73 donor.

    Still planning on the leak down test on the donor to confirm I have a good one (I suspect it is).


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    Last edited by adwebinc; 12-30-2017 at 10:55 AM.
    '07 e65|N62 - Alpina B7 - Black Sapphire|Black|Loaded|GONE
    '02 e46|M54 - Orient Blue|Beige|'Vert|GONE
    '00 e39|M52 - Anthrazit Metallic|Grey|GONE
    '01 e38|M73 - Anthrazit Metallic|Schwarz|Shadow-Line|GONE
    '91 e31|M70 - Schwarz|Schwarz|M70|FOR SALE

    '13 328i Auto - Black Sapphire|Coral Red|Sport Line|GONE
    '05 545i SMG - Jet Black|Black|Bamboo Anthracite|GONE
    '07 335i Auto - Montego Blue|Grey|GONE
    '05 545i SMG - (Euro Delivery 7/22/05)|Black Sapphire|Auburn|GONE
    '97 528i Auto - GONE

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