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BMW M70, M73, S70

BMW V12 Engine Program (as of January 2007)

This information starts with a basic rebuild of the BMW V12 to stock specifications, then options are listed for different horse power levels.  Each option builds on the previous.  The additional parts and labor are noted.

BMW did not intended for the block to be bored, therefore all Power Plant rebuilds utilize steel liners, installed, bored and honed to the final size.

Certain detail work is performed on all engines, starting at the stock rebuild level.  Some of these details are: balancing and blue printing, high performance 3 angle valve seat cut, radius head bolt holes, chamfer and radius sharp edges in combustion chamber and piston tops.

There are some parts that are not included in the regular rebuild price.  These items are usually only needed on extremely high mileage engines.   These parts include : oil pump, rocker arms, hydraulic lifters, intake valves.  These parts are assessed during disassembly and inspection.  The customer is then notified as soon as possible, of the total costs involved.

A long block rebuild from The Power Plant is similar to what you would get from BMW if you ordered a remanufactured engine.  It is a bare engine from oil pan to valve covers, with no ancillary parts.

6 Liter M70 Engine

Stock Rebuild - long block


  • custom forged pistons w/ rings

  • clips and pins 

  • main bearings 

  • rod bearings 

  • rod bolts 

  • main cap bolts 

  • crank bolt

  • water pump

  • pilot bearing 

  • oil pump chain 

  • timing chain 

  • timing chain guide rail - upper 

  • timing chain guide rail - lower 

  • timing chain tension rail 

  • gasket set

  • head gaskets 

  • head bolts 

  • intake gaskets / mounts

  • block dowel pins - oil filter 


  • sleeve, bore and hone block 

  • replace exhaust valve guides 

  • micro polish crank

  • surface heads 

  • balance crank  

  • balance rods, end to end 

  • balance pistons 

  • recondition valves 

  • cut seats

LABOR @ 75.00/hr

  • disassemble engine, clean and inspect parts 

  • peen, paint, prep for assembly  

  • pre-assemble engine, check specs  

  • final assemble engine long block  

  • install intakes and ancillary parts on engine  

  • TOTAL ENGINE stock long block               -            -            $ 10,589.00

BMW V12 Engine Options (as of June 2006)


  • 5.6 liter 375hp / 405lbs/ft / 86mm bore / CSi crank - 80mm stroke / 5576cc displacement
    CSi crank                                           $4,000.00
    TOTAL engine            -            -            -            -           $14,589.00



  • 5.6 liter 405hp / 415lbs/ft / 86mm bore / CSi crank - 80mm stroke / 5576cc displacement
    CSi crank                                                       $4,000.00
    schrick cams - 264 duration                        $1,490.00
    port and polish cylinder heads - 24hrs       $1,560.00
    match port intake gaskets - 6 hrs                 $ 390.00
    extrude hone intake manifolds                      $ 950.00
    TOTAL  engine            -            -            -            -           $18,979.00


This kit changes the stroke of the engine from 73mm to 86mm, the bore from 84mm to 86mm and the compression ratio from 8.8/1 to 10/1.   The 6.0 conversion on an otherwise stock rebuild makes 405h.p. & 425lbs/ft.

  • custom billet crankshaft - 86mm stroke  
    crank gear kit  
    Csi head gaskets  
    custom pistons, rings, pins, clips  
    TOTAL engine            -            -            -            $ 15,279.00


This package is a continuation of the complete rebuild of the engine with the upgrade to 6 liters.  The 6 liter parts change the stroke of the engine from 75mm to 86mm, the bore from 84mm to 86mm and the compression ratio from 8.8/1 to 10/1.


  • 425hp / 435lbs/ft / 86mm bore / 86mm stroke
    custom billet crankshaft - 86mm stroke
    add - schrick cams - 264 duration
    add - extrude hone intake manifolds
    add - larger fuel injectors
    crank gear kit
    Csi head gaskets
    add - dyno tune - break in, tune, map fuel & timing, and burn custom chip set
    TOTAL engine            -            -            -           $ 19,609.00


  • 440hp / 445lbs/ft - completely civilized, stock drivability
    custom billet crankshaft - 86mm stroke
    schrick cams - 264 duration
    larger fuel injectors
    crank gear kit
    Csi head gaskets
    extrude hone intake manifolds
    dyno - break in, tuning, map fuel & timing, burn custom chip set
    add - port & polish cyl heads
    add - match port intake gaskets
    add - bored out stock throttles
    add - custom headers w/ceramic coatings
    add - lightened and balanced conrods
    TOTAL engine            -            -            -            -            $ 26,584.00


  • 455hp / 445lbs/ft - completely civilized, stock drivability
    You can pick up another 15 hp by adding the larger MAF sensor and air filters
    TOTAL  engine            -            -            -            -            $ 27,534.00

    The larger air filters can not use the stock air box, therefore some may not be inclined to use this additional feature.   We are however working on a cover to render a cool air intake.  Although it will not look factory original, it will be a nice clean installation



  • 485hp / 465lbs/ft - may not meet emission standards - rumbly idle / 7000 redline
    custom billet crankshaft - 86mm stroke
    add - custom steel connecting rods
    re-engineered pistons 10.5 / 1 compression
    change to - custom roller cams - redline of 7000 rpm
    add - roller cam valve train conversion for M70
    add - high performance valve springs
    add - titanium valve spring retainers
    port and polish cylinder heads
    match port intake gaskets
    change to - modified intake manifolds
    change to - custom big bore throttles
    custom headers w/ceramic coatings
    large MAF sensor and air filter kit
    fuel injectors
    crank gear kit
    head gaskets (Csi)
    dyno - break in, tuning, map fuel & timing, burn custom chip set
    TOTAL  engine                        -            -            -           $ 38,494.00


  • 530hp / 465lbs/ft - will not meet emission standards -  rough idle / 7500 redline
    custom billet crankshaft - 86mm stroke
    custom steel connecting rods
    11.0/1 pistons or higher
    custom roller cams - redline of 7200 rpm
    roller cam conversion for M70
    high performance valve springs
    titanium valve spring retainers
    larger intake valves (43.5 vs 42)
    larger exhaust valves (37 vs 36)
    port and polish cylinder heads
    match port intake gaskets
    custom intake system - indv. runner
    Electromotive engine management system
    custom headers w/ceramic coatings
    fuel injectors
    crank gear kit
    head gaskets (Csi)
    dyno - break in, tuning, map fuel & timing, burn custom chip set
    TOTAL upgrade with  engine rebuild            -            -            $ 45,694.00

Current ongoing project: OPTION F

  • 610 hp / 480 lbs/ft - smooth idle will meet tailpipe emissions / 7800 rpm redline

    This engine is a 6 liter bottom end build, with custom 4 valve per cylinder,  heads.
    Their design is based on the E46 M3 engine cylinder head - (S54 designation).  More
    detailed information is available for serious inquires.   
    Complete engine  $ 83,000.00


The Power Plant has an in house engine dynamometer and a cooperative arrangement with a chassis dyno shop.  Although performance chips can help an engine produce more power, each engine has its own characteristics that can be optimized by tuning the fuel and ignition for that engine specifically.  After-market performance chips are usually based on a stock engine.  On modified engines, especially stroker engines, custom chips are an absolute necessity if longevity, maximum power and low emission are desired.

With a dyno, changes in mixture and ignition can be adjusted for peak performance and clean emissions.  The power can be measured to an accuracy of 1%.  To get it right tuning on the street, would be guess work at best.

A major benefit, is a controlled initial run in of the engine, which can optimize performance and longevity. This just can’t be done on the street. The engine has to be put through load cycles.  A few minutes of running with a load on the engine, then a few minutes of idle to let parts cool and the temperatures normalize. The length of time and amount of load is determined by watching the oil temperature, blow by gasses and other indicators.  Then the load and rpm is increased in steps as the indicators show the progress.  With the engine properly run in from its new condition, all the wearing and sealing parts are correctly mated. The pistons, rings and cylinder walls will seal more completely and more evenly. Better sealing means more power.  More evenly means longer life for the cylinder walls and rings.

Another benefit is the ability to make a custom chip for the DME and optimize the fuel and ignition for maximum power. The full load and part throttle parameters can be changed to optimize power without changing the low speed and low load values required to meet emission tests.

Another benefit is the ability to verify that everything is working correctly, and there are no problems. From oil leaks or cracked spark plugs to main or rod bearings, almost anything can be detected and corrected.




The crank is made from a solid piece of 4340 steel billet.  This is the industry standard alloy and can be found in everything from custom hotrods to Formula 1.  These cranks are a full featured precision part.  They are designed to bolt in and use the standard BMW bearings.  They feature radius oil holes, knife edge counter weights, large fillet radius and nitrite hardened surface treatment.



With the recent interest in performance modifications for the BMW M70 engines, I have collaborated with a high quality and long established cam manufacturer to make an efficient and aggressive cam package.

This package changes the M70 valve train design from a pad follower to a roller type design.  The cams themselves are custom units made from a steel billet.

With the M73 engine having the components of a roller design we decided to incorporate those into the performance package for the M70 engine.  There are several advantages to a roller type valve train.  The two main attributes are the reduced friction and the ability to have a faster ramp design on the lobe.

These cams are designed to have a operating range to 7500 rpm.  Idle quality is very good with just the slightest hint of lope.  Depending on other tuning modification, the cams peak hp can be between 5700 and 6800 rpm.


                                                      Stock                /                Power Plant     
duration                               213                            245 int / 255 exh
valve lift                             10.4mm                            11.4mm
lobe centers                     112 deg.                           110 deg.



  • roller rockers
    spring retainers

    spring seats - inner
    spring seats - outer

    intake valves
    exhaust valves

    TOTAL CONVERSION         -            -            -            $ 1,157.58



Raising the redline from 6000 to 7000 and adding 11mm to the stroke, adds the same amount of stress as turning the engine 2000 rpm over the designed redline.  The stock rods are not strong enough, or long enough, so custom rods made from 4340 billet steel are used.  In order to maintain a stroke to rod ratio that is correct for the longer stroke crank, the rods are 3.5mm longer than stock.



For the 500hp version, the manifolds are extensively modified.  To meet the higher rpm band and additional air flow requirements, the plenum is enlarged and the runners are shortened.  This changes the tuning of the intake system which was originally designed for a torque peak at 4000 rpm and hp peak at 5200 rpm.  This engine has a peak torque at 4500 rpm and a hp peak at 5700 rpm.



These are custom, forged, high silicone content aluminum alloy, and designed specifically for what ever the application.



For this option, the stock DK throttles are completely disassembled and rebuilt.  While they are apart, the housing is bored to a 3mm larger diameter and a larger throttle plate of stainless steel is fitted.  The final product is a stock appearing throttle with 26% increase in area around the plate for more air flow.



For the 500hp version, custom, bigger throttle housings are made from aluminum billet and the servo motor from the stock DK throttle is transferred to them.  This way all the stock engine management system can be retained.  The stock throttle is 57mm diameter, the custom throttle bore is 65mm, a 33% increase in area.



For engines requiring  an alternative engine management system such as Electromotive or Motec, custom throttles are made from aluminum billet.  The throttle size is dependent on the application.  They are designed for cable actuation.



The headers are made specifically for the application.  They are a stepped design made form mild steel and then coated with a ceramic thermal barrier coating inside and out.  The coatings really cut the heat transfer and reduce under hood temperatures dramatically.   The step design is the latest in “state of the art” techniques for extracting the most power from an engine.



From the BMW technical information system - “the block has an increased concentration of silicone crystals at the cylinder bore surface during the casting process and can not be machined.”  For rebuilding purposes, we bore out the cylinders in the block to accept a steel liner.  The block is then heated and the steel sleeves are slid into those bores.  As the block cools it shrinks to a tight fit around the steel liners.  The new steel cylinders are then honed to the final bore dimension and the block is decked.  This process is also used by BMW on some of its other late model aluminum block engines.



These are made of the highest quality stainless steel and are made to fit with all the stock BMW hardware.



To meet the air flow and rpm tuning requirements, a completely redesigned and fabricated intake system is needed.  The ports on the head are enlarged so much that the stock intake manifold is not thick enough to match the cylinder head port.



The engines making 500 or more hp also make about as much torque, and the original BMW clutch will not hold. For these engines the custom clutch and flywheel package is necessary.  A light weight, heavy duty, single plate disc capable of holding up to 800 ft/lbs of torque is used.



To use the above clutch, a custom flywheel is made. It is machined from billet aluminum, with a steel insert for the clutch disc friction surface.



BMW published specifications

Engine type                    bore           stroke            disp.            hp                    torque                 c. r.                   redline

M70B50                e31            84            75            4988            295@5200            331@4100   8.8            6000

M73B54                e31            85            79            5379            322@5000            360@3900   10.0          6000

S70 B56                e31            86            80            5576            375@5300            405@4000   9.8            6400


Connecting rods - 28 grams in one ounce  /  16 oz’s in 1 pound

stock BMW            526 grams (1.174 lbs x 12 = 14.09 lbs)
lightened steel    480 grams (1.071 lbs x 12 = 12.85 lbs)
Titanium            339 grams (0.756 lbs x 12 =   9.07 lbs)



L: BMW 850 engine - close up of headers in silver thermal barrier coatings
R: BMW 850 engine - close up of headers in black thermal barrier coatings



BMW M70 cylinder head on flow bench


L: V12 with polished intakes on dyno
R: BMW 850i engine on dyno - dyno’ed in 2001 this engine is a 6 liter conversion with  Electromotive Tec2



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and Anthony Vanderlinden - Wet Dog Publications
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