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Thread: e30 M20B25 DUAL CAM HEAD SWAP

  1. #1
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    e30 M20B25 DUAL CAM HEAD SWAP

    I have a e30 m20b25 motor on the bench. I have been told about a possible pre 1993 dual cam head swap for my motor. I have herd of people swearing up and down they have done it and it goes right together yadda yadda. That it has to be the old pre 93 s50 non vaneos motor. I also have herd no. Whats the scoop?! Please help

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    No!!

    There is an uber rare dohc head in existence, but you'd have a better chance tracking down the pot of gold at the end of a rainbow.

    The people you are referring to were probably talking about swapping in complete 24v dohc engines like the M50/52 or S50/52
    Last edited by moberg12; 11-02-2011 at 06:20 PM.

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    Even if it was possible (I believe Alpina made the head that Moberg is referring to btw), it's far, far better to get a complete M/S50/52 if you want DOHC.
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    I was reffering to an m36 i believe pre 1993. Im good on a motor swap. To much work fab and bs. Plus if my Chiltons and Haynes are correct (unless you mod the shiz outta either one) they both, twin cam and single produce about the same amount of HP's stock. Not looking to get super crazy or do a full motor swap. So what was the true difference between the older m20's and the newer twin cam desighn??? Looks like the same block and the cylinders are spaced the same. Same amount of head bolts etc...

    I stand corrected unless its the 95 or later twin cam motor out of an M series producing 240hp...
    Last edited by akstewie84; 11-02-2011 at 07:28 PM. Reason: Automerged Doublepost

  5. #5
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    well for one the m20 was the last to have a timing belt, if im not mistaken, all the new dohc are timing chains

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    Quote Originally Posted by akstewie84 View Post
    I was reffering to an m36 i believe pre 1993. Im good on a motor swap. To much work fab and bs. Plus if my Chiltons and Haynes are correct (unless you mod the shiz outta either one) they both, twin cam and single produce about the same amount of HP's stock. Not looking to get super crazy or do a full motor swap. So what was the true difference between the older m20's and the newer twin cam desighn??? Looks like the same block and the cylinders are spaced the same. Same amount of head bolts etc...

    I stand corrected unless its the 95 or later twin cam motor out of an M series producing 240hp...

    The blocks might look the same but they aren't. There are certain parts that will fit the M20 but bolting on an E36 24v head isn't one of them!! Coolant jackets won't line up, timing chain vs. belt... It just doesn't work

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    even if you look past the fitment issues. you are talking about putting a chain driven camshaft head on a belt driven crankshaft block.


    24v swaps are cheap and dont require any real fab work. you can buy every single part to make the swap a direct bolt in. the only thing you need to fab is the exhaust. even then, if you wanted to cheap out you can just have the 24v headers flow directly into a stock e30 325i exhaust system. so you only have to fab that small part of the exhaust. which even if you take it to an exhaust shop it should not cost you more then $110 even if they rape you.


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    I was reading about having to swap brake boosters and some clutch stuff around. That doesent have to be done does it? I thought the OBD1 version might just bolt in. Here is the link im reffering to.: http://www.rmeuropean.com/bmw-e30-m50-swap.aspx

    Hay look I found a website that regrinds a stock cam to make a semi roudie cam for the e30 single overhead head for only $191!!!
    Better than spendin 500 on a shriek!!
    http://www.iemotorsport.com/bmw/E30-...0cam272re.html

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    swapping a brake booster is the same as removign and replacing the original. which takes all of 20 minutes if you have the motor out to do a swap and arent rushing to get it done.


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    And to answer the question about the power differences between the motors, the '92 e36 325i had 189hp and 184 ft-lbs of torque. That is compared to the '91 and earlier e30 325i making 167hp and 164 ft-lbs of torque. Both engines are heavily detuned in an attempt to balance between fuel economy vs power, but due to the twin cam head there is greater potential for power out of the e36 motor. It is capable of flowing more air, thus theoretically able to make more power if modified to make use of said flow. But as stated, due to the differences in timing chain vs belt and the passage mating issues, you will not be able to just swap on twin cam head. The amount of time, effort, fabrication and money to get a twin cam head onto a M20 block would far exceed that of swapping in an e36 M50 or S50 motor.
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    Quote Originally Posted by Stück View Post
    I'm marginally ashamed to occupy the same state as this individual.
    Well it is a big state.
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  13. #13
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    3cars-36v. Math FTW!
    And I'm guessing there are TONS of other people in the state you're ashamed of sharing it with before this guy.
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    Quote Originally Posted by moberg12 View Post
    No!!

    There is an uber rare dohc head in existence, but you'd have a better chance tracking down the pot of gold at the end of a rainbow.

    The people you are referring to were probably talking about swapping in complete 24v dohc engines like the M50/52 or S50/52

    I read up some on that head, and there was only maybe 4 produced and all of them were prototype / one off kind of deals that never "officially" made it into the mainstream market. Alpina (or maybe Hartge?) decided that it just cost too much to produce apparently.
    Last edited by draccent; 11-03-2011 at 06:23 PM.
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    Quote Originally Posted by stück View Post
    i'm marginally ashamed to occupy the same state as this individual.
    lmao

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    Hay "STUCK" from huston Texas? Texas sucks, and you can suck it.3 Alaska's fit in TX Ha ha. The real question was not if the swap was simple or not. That if it was possible with little or no modification. Fabbing different pullies isnt an issue. I have spoke with Alpina I.E., , and many other companies about there twin cam set ups. The major problem is that there wasnt water jets w\cad programs back then Nore any blue print specs, so i cant reproduce there fab parts. I have the capability to cut these pieces. I have also tried to get ahold of the build specs for the long lost piece's and head desighns. I have a full mechien shop available at little or no cost with CAD and a WA jet table.... Anyone? Buler? Buler?

  17. #17
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    you cant produce a cylinder head using only a Water Jet. you need a full CNC 5 axis milling center to machine a cylinder head from scratch.

    even if you dont pay labor costs .. the amount of time it would take to design the program, the money it woulld take to buy the block of aluminum, the tooling and the electricity it would take to run the CNC that long would cost considerably more then an s52.

    if you want to spend months and thousands of dollars designing something inferior to whats cheap and readily available already .. go ahead and waste your time/money.


  18. #18
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    the 24v head was made by Racing Dynamics:



    - My E30: Project 325i

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  19. #19
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    Quote Originally Posted by akstewie84 View Post
    Hay "STUCK" from huston Texas? Texas sucks, and you can suck it.3 Alaska's fit in TX Ha ha. The real question was not if the swap was simple or not. That if it was possible with little or no modification. Fabbing different pullies isnt an issue. I have spoke with Alpina I.E., , and many other companies about there twin cam set ups. The major problem is that there wasnt water jets w\cad programs back then Nore any blue print specs, so i cant reproduce there fab parts. I have the capability to cut these pieces. I have also tried to get ahold of the build specs for the long lost piece's and head desighns. I have a full mechien shop available at little or no cost with CAD and a WA jet table.... Anyone? Buler? Buler?
    English man, its really pretty simple.
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