N62 Z3 Part 18: Fabrication (Engine & Trans Mounts)

Fabrication (Engine and Transmission Mounts)It's so close now I can almost smell the trunkfloor failing


First step of the engine mounts was to make the bracket that bolts to the engine. The alternator bracket made this complicated on the driver's side of the engine. The passenger side is completely flat (like a normal engine mount) so is just a matter of drilling in the right spots

This will be reinforced substantially later but we need a base that mounts flush to the engine before doing too much else. The other side is just flat at the mating surface so it was pretty simple to do


Once the brackets were done I put the engine back in place and aligned it. I was happy to see the transmission tunnel was adequately clearanced, as the transmission not only had visible clearance around the bellhousing but the transmission mounts were no longer being "tugged" forward

After doing more research it ends up it isn't just important the driveshaft "points straight" as the laser alignment tool was determining, but rather what seems to be important is the relationship between the angle of the output flange and the input flange at the diff, as well as the angle of the driveshaft going into and out of the U-joint. So there was quite a lot to it - but now I knew where to take some additional measurements. Using an inclinometer I took the critical measurements and I then adjusted the engine height until the transmission flange was at the correct angle relative to the differential. This put me in a good spot, but I think I may still need to find a way to lower the transmission a little bit more so I might weld a thin but of sheet metal onto the spacers I made

I then aligned the engine laterally and this is where it ended up. The engine is now low enough that the strut brace fits over the intake as well, although its so tight that its rubbing against the intake manifold so will obviously not be used like that

I then double checked things and re-adjusted quite a few times. I think I have it looking pretty good at this point but the laser isn't perfectly centered and this was at the bottom of it's arc

I test fit the x-brace again with the engine at it's now finalized height and it is hitting the lower oil pan on one part, so I will just cut that bar off and reinforce it nearby. It is a very tight fit overall. The lower oil pan is also pretty banged up so I think I may go ahead and replace it before throwing oil in the engine

Oh and on that note I had to remove the steering shaft. It interfered in a very bad way with the exhaust manifold. My original plan was to use the steering shaft from an E46 xi (AWD) model, as I know those routed the steering shaft around the front axles. I thought this would be suitable in my case but after studying it a bit more it simply wasn't going to work


A second idea was to move where the steering column exits the firewall. This was recommended a few times and in an ideal world it is what I would do. However this does add a lot of complications in it's own right just by virtue of, well, hacking the firewall up and moving the column. And it wouldn't even entirely solve the problems on the Z3 chassis, due to the angle of how the frame rail sits back there. All in all it just didn't seem this was the best decision


The solution I was hoping to avoid, making it a two-piece shaft, started to seem inevitable. I priced out what was needed, considered all other options a few more times because holy cow quality steering components are expensive, but ultimately I did bite the bullet and simply buy the parts I needed. Next to the engine, this is the second most expensive single part of the swap so far... but, I didn't want to cheap out with these parts. I also wanted to maintain the stock functionality of the collapsible steering column (an important safety feature) since I plan on driving the car on the street


I mocked up the general layout using some extensions while waiting on parts to arrive and removed the engine to be able to visualize everything a little easier

Then put the engine back in to ensure the orientation would work, I ended up having to adjust it a little bit and all in all the clearance is way closer than I was hoping. But it will clear in this arrangement

From the firewall side, the clearance is good to the engine but I may need a bit more clearance at the chassis. The steering shaft is bolted to the chassis and does not really move much but at the same time, the shaft I am using is a DD shaft so any slight rubbing against the chassis could become a really big nuisance if the chassis is flexing or anything

I then unravelled some of the wiring stuff to see how the OBD port would sit, I just kind of wanted to see it a little more "completed" to be honest, haha

Power steering stuff is a mess right now but I don't think it will be too complicated to figure out. Not a priority either

I also decided I didn't want to stack additional spacers underneath the mount to lower the trans the last little bit, so I will be creating a custom transmission mount after all...


My idea for this was pretty simple and I will use my existing spacers on the sides where the mount bolts to the chassis. I stacked some nuts with various washers to raise the spacers to raise the spacers the right amount above the existing mount and then ground off the little alignment nubs to allow the steel plate to sit flat against the mount

Originally I was planning on welding the new part spanning the middle width to the existing outside pieces but eventually decided to just make new side pieces, this also simplified the production process substantially, as we just had to make a piece that essentially laid flat on top - instead of making a piece that bent "under" the outside pieces. It also allows me to have a jig to make another if I need to for any reason. To make the adjustment was pretty simple, I just had to drop the spacers down by the height of the existing side pieces


This is with the middle section party bent to conform to the mount

Deja vu...

The mount finished, whew! It was pretty simple all things said and done but glad it's done now. It was fully bolted in when welding to try to prevent distortion, I just wanted to take a bit of a work in progress picture as I knew it was missing some of those

In hindsight, I should have drilled the center trans mount holes a little differently. The transmission sits on these at an angle (as you can clearly see) so the effect of this is that as I stacked the plate on top to make the custom mount the holes on the top plate were moved inwards slightly. It wasn't a big deal, just filed them outwards on both sides an even amount


Installed! It's funny, I keep thinking back to how I thought the stock transmission mount would work... I want to go back in time and call myself a freaking pendejo

Great news though is the alignment is now excellent. This is with the rear shaft angled exactly as it should be in operation. It's pretty much a straight shot from the trans back to the driveshaft now

Even got a video...

Awesome! Now I can finally move on from the freaking transmission mount... the engine has to come back out soon to work on the stereing shaft but before then I took measurements on the adjustments needed on the shifter carrier so I can get that welded up

The last thing to work with the engine still in was the engine mounts, which required getting the engine at the correct height, as the angle of the engine ultimately sets the angle of the transmission output, which ideally should be the same angle as the differential input. This was a pretty simple process and I actually did not have to make any adjustments to where I had the engine mocked up. I had a digital inclinometer with a magnetic base, I simply zeroed it out on the differential input flange then rotated it 180 degrees to measure the transmission output flange. I also made sure to place it on a flat surface on both flanges and oriented vertically


Zeroed out on the differential input flange

Exactly 180 degrees when on the transmission output flange, indicating they are exactly parallel

Next I took the same measurements but with the angle measuring the horizontal angle and it was also correct in this plane

It would have been quite a headache to say the least if these measurements were far off. They were dead-on which confirms that my math up to this point has been correct and that I lowered the transmission the correct amount. I may end up over-correcting a little bit when I make the engine mounts as ideally these angles should match under load when the rubber mounts will flex slightly, so I may add a little "upwards" angle at the transmission, so when under load which flexes it downwards, it ends up orienting itself straight. The engine has plenty of room to move downwards slightly, which will introduce naturally this upwards angle at the transmission. I will measure a stock BMW and probably just match whatever angle that is at for the final install. But we are talking about fractions of a degree - so being "zeroed out" in the neutral position right now gives me plenty of room for adjustment


I also marked on the chassis roughly where the slave cylinder sits so I can bend a hydraulic line for the clutch next time the engine is out since this car was originally an automatic. But next up is engine mounts!


The first thing was to double check every measurement everywhere I could to make sure the engine was oriented straight in the vertical and horizontal planes and then after any adjustments to check the flanges for being parallel again. I knew the engine was a little "crooked" from how the transmission mount was loaded, so I raised the engine then put some spacers between the oil pan and the subframe - adjusting them until it sat evenly from side to side, double checking with my caliper and the inclinometer. I love the inclinometer - I zero it out on the middle top of the engine and compared that measurement to the measurements taken at the same point on the chassis. After a lot of tweaking, I got it within .2 degrees which is perfectly fine for me. The passenger side is the slightly lower side which seems fine to me (under load the driver's side gets compressed)


This was the engine in it's final position

Oil pan is nicely parallel to the x-brace now. Fitment is tight but it is not touching. It actually has just a smidge more clearance than the E36 I have on my lift

Transmission tunnel will need just a tad more clearancing... its not touching, but it's way too tight for comfort

So now for actually building the mounts!

Mocked the shaft up roughly in shape. I put the actual U-joint I'll use for the shaft in place too, to get an idea for how big it is and where it'll sit

Used a thick heavy grade washer as the base for the mount side

There was a lot of back and forth deciding what material to use to construct the mount out of. Ultimately we ended up using a U-bolt which we cut to fit, the reason for this was due to a few factors - firstly, the bends we needed to go "over" the steering shaft were already there so we wouldn't be fatiguing them more bending them to shape, the material was a high enough grade that we felt it was strong enough and it was easy to see what we were doing with these bars instead of thick flat metal


It also made it a little easier to solve the complicated puzzle that was going on in there. We had to be clear of the steering shaft, but still be able to remove all 4 engine-side bolts and remove the engine mount nut, so there was a lot of mocking it up with vice grips, checking fitment for ratchets/sockets/etc then making small adjustments. All the bolts are accessible with a ratchet and socket except for the one right near the headers, the upper rear one, which is accessible with a wrench


First two were cut and tack welded in place. These were stick welded, due in part to the stronger nature of stick welds and because it was hard to fit the mig gun in there and get it at the correct angle

Then it was removed, fully welded up with a reinforcement and reinstalled to take measurements for an additional reinforcement

It looks really rusty, but it's just that brown welding residue. The final piece of the puzzle here was to get the rear reinforcement welded on then we can move on to the much easier passenger side. Below is the last reinforcement before being welded into place


After being welded we cool it buy just throwing it in the swamp cooler duct...

Next was to repeat the process for the other side

Checking fitment with the A/C compressor and have also installed the exhaust manifolds

The initial version after being tack welded. Two additional reinforcements were added and the placement of the attachment to the engine mount location and the overall shape of the design was given a lot of consideration

This is how it ended up... checking that I can tighten the nuts

This is how this side ended up looking

They will get painted when the engine comes out but for now I checked all the fitment everywhere

The output flange was 179.9 which I think is fine. I may also end up adding another washer under the driver's side mount to raise it up just a tad and that will likely bring this back to 180

The engine bolted into place! It's hard to see but both the mounts are there

A video makes it a bit clearer

Good clearance around the subframe/steering rack

The engine is quite far back...

And just admiring it with the engine installed

Next up is to take the engine out so I can ...do the rest of the swap! Next is steering shafts, driveshaft, etc

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