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Manimal's M20 Swap; Duct tape, zip ties, and a hammer

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Finally after a long hiatus I'm getting back to my project.

1976 Autotragic with an M20.

This will be an attempt to make the swap as easy and inexpensive as possible. If you can do some rudimentary welding(or have a friend who likes beer) and have some determination, then you can do this swap. I'll be documenting this project in great detail and writing up a conversion manual with details on all the parts I use and recommended tools which you probably don't have, but don't cost too much.

I will be weighing everything I can for the swap and in general on the car and adding it to a spreadsheet. Hopefully by the end of the swap I'll have a better idea of where to place things to improve the weight distribution beyond what seems correct by looking at it. I plan on getting the weight distribution back to stock or slightly more rearward after the swap which may include ballast at the rear of the car.
Now to jump in part way through.

Time to make some room, funny that in my large collection of tools I don't have one of those 3lb mini sledge hammers...this'll work.

After some hard pounding I discovered my 20oz ball-peen hammer to be more useful and manageable. I clearanced the firewall next to where the original fuel line and vent tank hoses came out and more obviously the sill above to make room for the intake manifold. The green line is where I would do it if starting from scratch, I'll probably hammer a bit more on it. The blue circle is where I believe there will be interference with a bolt on the transmission which wasn't in place when I did the test fitting.
IMG_0594 edit.jpg

The water neck on the back of the head is quite close to the firewall, even after some hammering. As it sits there is about 5-8mm between the firewall and the heater box which is directly behind that water neck.

Much more steering link clearance compared to the dan williams style mounts!

The cardboard template was made off my nicer car with an uncut nose. The crank pulley is almost exactly in the same place fore/aft as it is on the M10! Ignore the ugliness of this tube frame nose support, it was made with a HF 151 mig a few years ago. It was made from 1" 0.065 square and way stronger than I intended. I was able to stand on it and jump up and down w/o any noticeable flex. I'll be rebuilding it with a mix of 1.5", 1", 0.75", and 0.5" 0.049 wall tubing, hopefully dropping 5-6lbs from it's current 26lbs.

Modification to the passenger side subframe/motor mount interface. I elongated the holes about 10mm with an longshaft electric die grinder and carbide burr. I highly recommend getting one, I used a harbor freight unit(~$40) for a while before biting the bullet and getting a makita GD800c. It's worlds nicer, but the HF unit will work and be useful for other parts of the project. Astro Pneumatic sells an 8pc carbide burr set for ~$50, I'd buy them again in a heartbeat. Edit, since then I bought a makita GD0601, $100, but can often be picked up for $80 when the tool companies do promotions. The GD800c is a beast, but the 601 works great for everything I've done so far on the car. 

Though not in the final position, the oem e30 exhaust downpipe fits!

This is the radiator and expansion tank I'll be using. The radiator is an aluminum ebay unit which runs about $125 shipped. The expansion tank is from a volvo 740.
Volvo 740 Radiator Expansion Tank.JPG
BMW M20 swap radiator VW Mk1 golf scirrocco.JPG

Some pics of the transmission nubs to shave off. Second pic, upper circled area is solid and needs to be removed.
IMG_0580 edit.jpg
IMG_0578 edit.jpg

Edited by manimal
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The previous post was migrated from the new blog section, posted back in early march, and after producing a batch of mounts I fell off the wagon agian.


Pics to come.

Back to it and making progress.

The car is sitting "on blocks" to get it high enough so I can work underneath while the suspension is in its static state. First order of business was to make/weld on new center support bearing mounts. You could cut the old ones off and re-attach them, but I found the old CSB mounts quite handy for holding the driveshaft so I could make small adjustments/take measurements until I was satisfied with it's position. The e30 driveshaft has perpendicular slots where the CSB bolts to the car, reverse of the 02 which has captured nuts that can slide fore/aft. To give myself a little bit of wiggle room I slotted the CSB mounts which were being welded to the car so I could also make minor side to side adjustments if necessary.

I spent a long time trying to get the alignment as close to perfect as I could using a few squares, a laser pipe level, and a magnetic angle cube. Those tools helped immensely compared to the first time I did the swap with potentialm20. Finally satisfied, it was time to move onto the transmission tunnel.

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Pics to come

Initially I tried to hammer out the tunnel and cut just the top off to make room for the Getrag 260. I realized this wasn't going to work and the easiest solution would be to remove most of the factory tunnel. Unfortunately I had already beat it into submission so I was going to have to weld a nice square edge to some heavily wrinkled and quite thin sheetmetal.

Using cardboard to make a template I and some math class skillz, I traced out the pattern in two sections onto some 0.065 sheet metal.

I cut out the sections with a grinder spinning a thin cut off disc. I used to use the harbor freight discs, but bought some nice 3m green corps discs off ebay for about $1/ea. Those discs blow the HF ones away, they cut faster, last longer, and produce less dust/stench. Never again will I buy the HF garbage cut off discs.

I don't have a sheet metal bender, but I do have a press and some random scrap metal. After some digging I found an alloy T-channel and 1 1/4" OD steel pipe, which combined to make a jury rigged bender that gave a nice curved bend. Amazingly freehanding both parts I was able to make both pieces match up almost perfect. I stuck a twist wire wheel(from HF, some of their stuff works ok) on the grinder and cleaned both the surfaces off. If I were to do this again, I would pull the engine and remove the undercoating 2" from where I was about to weld. That seemed to be enough distance to prevent it from catching on fire. I didn't end up doing that and had quite a few nasty little fires to deal with.

I held off cutting my shift platform hole since I'll be using a later G260 with the alloy shift arm shift support vs the early steel type. Not having the other trans pulled from my parts car yet, I decided to make a mark 6" from the trans output flange as a point of reference for cutting the hole in the future.

After tacking the sections in place I tried to close up as many of the gaps as I could. In the end I had quite a few large gaps of up to 1/4" to fill while trying to weld 0.065 to the factory 0.040(?) metal. Many many tack welds later I have a sealed tunnel. The easiest way to check for little holes I found was to put a super bright light, 20watt LED worklight, under the tunnel. Then with the garage lights off I looked for light near the welds from inside the car.

I made it larger than necessary, but it gives you an idea of approximately how big the tunnel needs to be.

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  • 2 weeks later...
  • 2 weeks later...



I have a modified E30 subframe, camber/toe adjustable, with trailing arms and the whole bit. Bolts right up to the 02 studs.

Might save you some time, you would still have to sort out the diff mount. But that part is super easy.


Took it off my recent 2002 that I've parted out. Located in Portland. 


You can email me at [email protected] if you are interested.

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