Jump to content
  • When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.

M20 Conversion!

Recommended Posts

hehe... who wants their name/s on this one!? I know a BUNCH of you guys have done this, working on it, etc. Also Richard has his writeup at .co.uk, but would you (who have actually done it) have anything to add or any other insights or tips... Just because there are other writeups elsewhere, doesnt mean we cant have our own definitive version here. :)

Link to comment
Share on other sites

  • 1 month later...
  • 4 months later...

Updated throttle cable section 12/31/07

Here's some helpful info I've compiled. Much of the rest can be had from “Six Into Two Does Go” which is available at: http://www.bmw2002.co.uk/pdfs/6%20into%202%20Goes.pdf


Its become popular to use the radiator from an air-conditioned A2 VW golf/jetta (1985 to 1992). It fits into square tail light cars only if you cut off the additional upper front frame rails for the big bumpers (a bit time consuming). Any 12 inch electric fan fits nicely on the front of these radiators. The VW radiator requires a suitable overflow tank - the e30 one will do, so will the VW one. I got mine new at an online supplier for around $20.

Engine mounts:

It is possible to make your own mounts by following the drawings and directions from the text "Six Into Two Does Go." The Dan Williams mounts will save you time and money, especially if you don’t have a welder and the necessary skills.

Throttle cable:

The best choice is probably one from Lokar, available in many lengths from places like www.jegs.com. I used a Honda CVCC cable as recommended in "six into two does go." Its functional but too long to be ideal, not to mention rare at the junkyard.

After attaching the cable to the m20 Throttle body (the easy part) and the gas pedal lever (requires some fabrication) you may notice that there is not enough "resolution" when actuating the gas pedal. It will likely have half the travel of the stock throttle. Fixing this may require a bit more fabrication, possibly lengthening the arm on the throttle body.

Stock Tachometer use:

Directions from Chuck L. on how to modify the tach:

As far as the tach, look at the following link:


I did it and it does work. I am not strong in the whole electronics thing, really don't know what a potentiometer is and can't solder worth a shit but I'll give you the quick rundown of how I did it:

1. Go to radioshack and ask for a 5K ohm 10 turn potentiometer. I had to buy a 10K ohm b/c that is all they had. (mine looked like a little blue plastic box about a half an inch long with three pins sticking out the bottom and a screw coming out the side)

2. Solder a couple of wires to the tabs on the potentiometer thus making a pigtail. Test the pot with your multimeter to make sure you can increase/decrease the resistance with the screw on the pot. Mine only worked on the middle pin and either of the outside pins.

3. Pop the needle off the stock tach (pry with screw driver) and remove the face of the tach (2 screws)

4. Behind the face there are 2 green wires. The only wires directly under the face of the tach. (there are 3 green wires below that are connected to the external connections...not those)

5. Solder the pigtails from the potentiometer to those green wires (it doesnt matter which wire you connect to... just want to bridge the pot between the 2 wires) I soldered directly to where the wires connect to the circut board. Make sure you can still screw the screw on the pot.

6. Put you tach face and needle back on.

7. Attach the tach along with an aftermarket tach ($15 clearance special) . I just sat the tach on the dash and plugged in the stock connectors. Temporarily wired the aftermarket to the starter wire (always hot..careful), the - coil terminal, and grounded on the block.

8. Start the car and screw the screw on the pot until both tachs match and you are good to go. I siliconed the pot onto the metal housing of the tach..inside of course.


Once you have the potentiometer set you could measure its resistance and just replace it with the appropriate resistor for a clean install that will never change its setting.

Fuel pump:

"Six Into Two Does Go" recommends the use of the older e30 and e21 type fuel pump setup, which is actually two pumps, an in tank pusher and a main pump downstream. This isn't necessary, but the two-pump system may have been the preferred design for BMW engineers. Even though it was phased out on the 325i, it was continually used on the M3. The advantage is that you can fit a surge tank between the two pumps to prevent fuel starvation in hard cornering. Spares are also easily available in the junkyard if you're on the cheap.

To save some time and aggravation, you can fit just one pump in the tank. 1989 to 1991 e30 bmw's (non m10) and 1991 e30 318is (m42 engine)have a single in-tank pump that screws into the stock 2002 tank.

E30 318is fuel pumps are have the right length to fit earlier fuel tanks perfectly. The 89-91 325i pump is shorter. The Later 2002 tanks have more depth.

The pickup of these pumps can be lengthened but the fuel gauge sender will still read empty when its not.

The 1989-1991 325i pump can be had much cheaper than the 318is pump.

Canada Matt's advice:

"I'm using a main pump and prepump from an '82 320i. If you have the earlier tank (210mm depth I believe) its a good fit. If you have a later tank (230mm depth I believe) then, well...not quite perfect. Right now I am using a later tank, and just keep some extra gas in there. Note I am NOT using the e21 accumulator setup, as the one I had was junk, lines were rusted, etc. Seems to work fine, despite all the posts you read that indicate otherwise. I have taken the car to the track a few times, works fine, no fuel starvation issues.

I also have a in-tank unit from a 90 318is sitting at the shop. I test fitted it; same deal, its good with the shorter tank, but has a bit of a reach for a longer tank.

My advice? Call Dave Varco, tell him the depth of your tank, and he will sell you an e30 in-tank pump modified to whatever length you want. I believe he sells 'new' units that he modifies. The only caveat is that the fuel sender is NOT lengthened, so it will still read empty when there is gas in the tank. Better than the e21 setup IMHO, as you have less moving parts, don't have to bolt the main pump under the car, and don't have to worry about an accumulator or anything."

Fuel Lines:

Its highly recommended that you run new fuel lines under the car. If your car originally had the plastic main line that runs through your interior it would be very risky to pressurize it with an EFI fuel pump or even as a return line. Originally the fuel pump drew a vacuum on this line so a dangerous leak wasn't nearly as imminent - it would simply suck air. Under the pressure an EFI system sees, a leak would quickly soak your carpet and whatever else with gasoline, causing a nasty fire with the right spark.

The stock under car metal lines may have corrosion so at least check them if you are bent on reusing them. And carry a fire extinguisher. EFI fuel system leaks have been known to help cars burn to the ground faster than you can blink.

Here's a tutorial on building high pressure fuel systems:



Coming right off the engine you have three options:

1. MSDS shorty headers

2. Two stock front exhaust manifolds (Be sure to use two 2.7 manifolds or two 2.5 manifolds. They ARE different. Ask me how I know)

3. Make your own long tube header. None are currently available for the e30 that will fit. If you are lucky you may find an old Ansa header which Faq member Chuck69 says fits perfectly.

See this thread for pictures of how the Ansa header fits:


Most swaps use a single 2.25 to 2.5 inch exhaust, from a muffler shop or homemade.

It isn't too hard for someone with a mig welder and a sawzall to make an exhaust with u-bends, though it can be time consuming. The stock downpipe from an e30 is useful. Pieces can be cut up and reused. You can also make your own y-pipe or buy one.

Quiet, performance oriented mufflers that fit an M20 2002 are hard to find. A 6x18 inch straight through round Magnaflow fits perfectly under the rear of the 2002. But even with a resonator upstream it may be too loud for most people.

Driveshaft shortening:

Having it done by a shop usually cost around $150. I found it’s not too hard to do it yourself if you are careful. I used a dial indicator to make sure it was straight when I was done. I shortened it at the back end of the front section to reduce possible vibration. I didn't use a lathe, but it would be easier with a lathe to carefully cut off the end of the tube and prepare the shaft end. I used a die grinder and a cut off wheel held very still as I turned the shaft in a contraption made from the center support bearing and a pin held in a vice. I did have to use my press to put it back together after careful de-burring of the parts. If it does vibrate, take it to a professional for balancing.

Here's some online guides to shortening a driveshaft:



Clutch line:

I found that having a custom clutch line made at my local Parker store was only $30. It was alot easier to fit then the rabbit rear brake line option mention in "Six into two does go."


The euro market e21 323i 4 speed, getrag 242, aka m60 is an easy option -- as is the 5 speed version, the getrag 245. They are not as hard to find in the states as you would think. Several junkyards seem to have them. I found mine on Ebay for $75.

Using the 323i trans only requires hammering on the transmission tunnel. I used the shifter and platform from my 2002 4-speed and shortened the platform and the linkage to fit the stock hole in the tunnel. Now I get to keep my center console.

The E30 325 throw-out bearing IS different from the E21 throw-out bearing that came on the 323. There have been varying reports on which one to use. I'm using the 325 bearing because it made sense to me to use the one matching my flywheel. We'll see how it works.

To fit the E30 Getrag 260 (the transmission that came with your 2.5-2.7 M20 from the factory) would require major modification/welding to the tunnel. This transmission is fairly bulletproof but heavier than the 323 transmission. The front half of a e30 driveshaft would have to be grafted onto the 2002 driveshaft. It also lacks a mechanical speedometer hookup (It works electronically on the e30). A shifter hole may have to be cut farther back in the tunnel.

Quick trans run down (from Ben Thongsai?):

Stock 2002 4 spd: Getrag 232

Stock 320i/323i 4spd: Getrag 242, but the bellhousing is different depending on which motor it is attached to

E21 320i 5spd: Getrag 245 for 80-early 83 models

E21 323i 5spd: Getrag 245, but different bellhousing from the 320i trans, this is the trans most people want for an M20 conversion, it's small enough to fit in the 2002 tunnel, is a 5 speed, and has a speedo drive

E21 320i 5spd: Getrag 240 for the late 83 models, has the 2 piece case

E30 318i 84-85: Getrag 240 same as '83 320i but with no speedo drive and dual rear trans mounts (note that some '84-'85 318i's came with a ZF trans that is completely different)

E30 318i/is '91: Getrag 240 but with a bellhousing that fits the M20/M50/M42 motors, no speedo drive with dual rear mounts. You can mix and match this trans with the '83 320i trans and get a Getrag 240 that bolts to an M20/M42 and has a speedo drive.

E30 325/e/i/is: Getrag 260, bigger than any of the above transmissions, no speedo drive. Doesn't fit the 2002 tunnel very well without some "help." E28 528e '83-'88 also used this transmission, as well as '89-'90 E34 525i.

E28 528e '82 only: Getrag 265, bigger yet than the Getrag 260, but near indestructible under most usage, detachable bellhousing, has a provision for a speedo drive, will bolt up to an M20/M50/M42, good luck getting it to fit in an '02 tunnel without major surgery. (unless you have an automatic shell, then it's more likely)

M20 engine tips:

The single mass M20 flywheel can be lightened significantly, though it is debatable whether going past 17 pounds is safe. Aluminum flywheels cost $500 or more and weigh a lot less. The dual mass flywheel found on later eta's actually has weights and springs inside and cannot be lightened.

Word has it that the 323i flywheel is the lightest of all if you can get one.

The 325i head flows much better than the 325e. The “I” cam is also much better. A nice upgrade for either engine is the 323 cam, which is, of course, found mostly in Europe. It has about ten degrees more duration than the 325i cam, though lift may be slightly lower.

A good start for an M20 is the "Super ETA" engine which only came in 1988 e30's. It combines the 325i head with the taller 2.7 block, longer 2.7 crank and 2.7 rods. Throw out the less desirable cam and throttle body for the 325i pieces and you're set. It may be easier to build your own "Super ETA" by using a common eta short block, the SETA's unique pistons and an I head. You can find the pistons for your buildup by posting a want ad at places like www.e30tech.com. You can also use the stock 2.7 pistons, but many seem to think it will cause very low compression. However, the reported 7.5 to 8.34:1 compression ratio is ideal for boost.

E30 325i owners debate whether building this 2.7 stroker is worth the hassle. You can also build a 2.8 stroker with a forged turbo disel m20 crank. The 2.7 crank is cast, but apparently it doesn't break. The M20 is a very tough engine.

Personally, I measured the chamber volume on both the “I” head and the “E” head and found little or no difference. The chambers are differently shaped, which is why I used the SETA pistons.

A euro 323i head has smaller ports than an I, but its still an upgrade for an ETA engine, as it raises compression significantly and may have better flow.

Shaving the M20 head for increased compression isn’t recommended as they often crack along the water channels, though they can be welded there to prevent cracking. Aftermarket head gaskets (MLS style) are available to lower compression to a desired level, and are popular for boost applications.

Use the Metric Blue head bolts from http://www.mcmaster.com.

Part Number 91303A306 grade 12.9 bolts- $10.56 per pack of 5. This has become the defacto headbolt option for everyone at www.e30tech.com, including many who are turbocharging their cars.

325e exhaust manifolds look to flow a bit less than 325i manifolds. The output flange is also oriented a bit differently.

The 325i intake manifold is much larger than the 325e intake manifold. So is the 325i throttle body.

The 325i injectors and fuel pressure regulator flow more fuel than the 325e. For more flow many e30 owners seem to use easily available 19 lb ford injectors.

Later E30's ('88 on?) had better EFI computers that allow for re-programmed chips.

Other tips:

The stock 2002 diff will now be the weak link in your drive train. LSD's will wear out much quicker. Be careful over 200 horsepower - m20curtis is on diff number nine with his turbo m20. He said the LSD diff's hold up if you "don't drive like an idiot." The trick is to roll on the power, instead of shocking the ring and pinion. You can also graft on the whole e30 rear subframe and diff for bullet proof performance, though it will increase track width, require possible floor mods and make your car that much less of a 2002.

Cutting the excess sheet metal from around the stock radiator greatly simplifies the installation and stiffeners can be added later to the nose, if so desired.

Watch out for valve cover clearance issues. Cutting out the rain tray can help. So does replacing one of the rear valve cover studs with a bolt.

if you chose this swap, good luck. Some say a car isn't a BMW without a six-cylinder. While I may not agree with that, the additional torque and smoothness in a 2002 certainly makes for a unique driving experience.

Link to comment
Share on other sites

  • 2 years later...

With the M42 specific flywheel you can use a M42 starter. No need to change the starter pinion gear as required with the M20 conversion. This can be a problem if your starter shits the bed at the track or some parking lot. You can go to a parts store and buy a starter and throw it in the car. What if the car changes ownership and the new owner takes it to a shop and the tech is scratching his head why the new M42 starter doesn't work.

In regards to cost I have broken that down as well. Here the M20 conversion does have and advantage. M20 single mass flywheels are plentifully available in the US. These can be found used in mostly good condition for $50-100. The Euro M42 single mass flywheel is not a common item here in the states so they most likely would be purchased new. Pelican has them for $323. We purchased ours through a private party for $200 shipped, new in the factory BMW box. I haven't checked my dealer pricing yet.

Link to comment
Share on other sites

  • 1 year later...
With the M42 specific flywheel you can use a M42 starter. No need to change the starter pinion gear as required with the M20 conversion. This can be a problem if your starter shits the bed at the track or some parking lot. You can go to a parts store and buy a starter and throw it in the car. What if the car changes ownership and the new owner takes it to a shop and the tech is scratching his head why the new M42 starter doesn't work.

In regards to cost I have broken that down as well. Here the M20 conversion does have and advantage. M20 single mass flywheels are plentifully available in the US. These can be found used in mostly good condition for $50-100. The Euro M42 single mass flywheel is not a common item here in the states so they most likely would be purchased new. Pelican has them for $323. We purchased ours through a private party for $200 shipped, new in the factory BMW box. I haven't checked my dealer pricing yet.

agree with you dude...This is an instructive site. I would like to surf it all for considering 642-974 and its associated statements. Because 642-973 is very illustrious and in command now a days. So I am incisive for high-quality information about 642-982 and 642-983 at every site. And I should get fine resource soon.

Link to comment
Share on other sites

  • 1 year later...

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • BMW Neue Klasse - a birth of a Sports Sedan

    BMW Neue Klasse - a birth of a Sports Sedan

    Unveiling of the Neue Klasse Unveiled in 1961, BMW 1500 sedan was a revolutionary concept at the outset of the '60s. No tail fins or chrome fountains. Instead, what you got was understated and elegant, in a modern sense, exciting to drive as nearly any sports car, and yet still comfortable for four.   The elegant little sedan was an instant sensation. In the 1500, BMW not only found the long-term solution to its dire business straits but, more importantly, created an entirely new
    History of the BMW 2002 and the 02 Series

    History of the BMW 2002 and the 02 Series

    In 1966, BMW was practically unknown in the US unless you were a touring motorcycle enthusiast or had seen an Isetta given away on a quiz show.  BMW’s sales in the US that year were just 1253 cars.  Then BMW 1600-2 came to America’s shores, tripling US sales to 4564 the following year, boosted by favorable articles in the Buff Books. Car and Driver called it “the best $2500 sedan anywhere.”  Road & Track’s road test was equally enthusiastic.  Then, BMW took a cue from American manufacturers,
    The BMW 2002 Production Run

    The BMW 2002 Production Run

    BMW 02 series are like the original Volkswagen Beetles in one way (besides both being German classic cars)—throughout their long production, they all essentially look alike—at least to the uninitiated:  small, boxy, rear-wheel drive, two-door sedan.  Aficionados know better.   Not only were there three other body styles—none, unfortunately, exported to the US—but there were some significant visual and mechanical changes over their eleven-year production run.   I’ve extracted t
  • Upcoming Events

  • Supporting Vendors

  • Create New...