Welding motor mounts

[smooth]

I haven't seen any discussion about welding motor mount tabs on to our subframe instead of using either the E28 535i or M5 engine mounts. Has anyone tried this and not been able to get it to work or what are the main reasons for not doing this mod?

I'm finishing up my 24v swap and my dad is getting ready to start measuring everything up. I'd like to generate some discussion on how to mount 24v engines in our e30's as well as present a how-to when he and I get it figured out.

[Adrian_Visser]

Sorry you mean welding the aluminum mount arms to the stamped steel subframe? Where to begin... Why would you want the engine solid mounted to the frame anyway?

[smooth]

No, I'm talking about welding new mount tabs with the correct angle in order to use the stock e36 motor mounts (nothing to do with the mount arms).

[bzboardz]

random question...why dont you like the E28 535i or M5 engine mounts?

[ForcedFirebird]

random question...why dont you like the E28 535i or M5 engine mounts?

This.

There is no reason to fabricate anything when there are stock mounts available that work just fine. I have done many many swaps using the 535i mounts without any issues.

Only reason I could think of is you have the stock e36 mounts, some scrap metal and not $50 to buy the mounts?

[smooth]

The block is pre-drilled from the factory to move the mount arms forward.
If we move the mount arms forward and correct the tabs so the mounts are properly aligned, then we can shift the weight distribution of the engine without moving it forward or backwards.

The getrag 250, 260, and zf320 are all 20 inches from bellhousing to transmission mounts.
The M50 block is 10 3/4" from back of block to motor mount holes.
The M20 block is 11 1/2" from back of block to motor mount holes.
The e36 measures 30 3/4" inches from transmission mount holes to motor mount holes.
The e30 measures 32 3/4" inches from transmission mount holes to motor mount holes.

As a separate note, jamming motor mounts in from different motors and body series doesn't guarantee that the driveshaft is perfectly aligned. While it may be quicker to just use whatever kind of fits, it compromises the wear points of the drivetrain.

[1990m3]

Doesn't compromise it by much, drivetrain come out very straight. A number of cars have logged over 100k on this forum, post swap, on all used parts, without premature drivetrain wear. Your idea is good, but why reinvent the wheel on this one? Probably over 100 swapped cars on the forum, that's a lot of success

Personally, I'd go with Akg poly swap mounts, perfect forint in my car, 60+ track days with no issues

[smooth]

mainly started thinking about it because the handling changes noticeably post-swap according to all the threads I've read. If we can change the weight distribution by moving the balance point of the engine forward then we can get it back inside the wheelbase like the M20 was.

Check this out:

[FredK]

If we move the mount arms forward and correct the tabs so the mounts are properly aligned, then we can shift the weight distribution of the engine without moving it forward or backwards.

Wait, whut?

Moving the mount arms forwards or backwards while leaving the block in the same exact position won't do much of anything, except at an infinitesimally small level (the weight contribution of the mount arms themselves).

There is no more room aft to bring an M50 closer to the firewall, and changing mount arm position does nothing to change weight distribution, unless you're talking about engine tilt and affecting side to side weight balance.

The handling change is noticeable, but can be tamed with some camber plates. The rest is up to your use of the accelerator pedal. On the street it is nearly unnoticeable.

[smooth]

ok there's two different issues that we were trying to address here:

1. why are people using motor mounts from a different series in an upside down orientation instead of simply welding mount tabs where they are supposed to be at the correct angle?

2. and two, how to remove what appeared to be two less inches of distance from tranny mount to engine mount


What exactly do the e28 series motor mounts do? do they not move the bolts anywhere other than outward on the subframe? if that's all they do, then why not simply weld a reinforcement box with the correct angle?

if they move the bolts either forward or backward then the tabs and/or mount arms need to move. But if they don't then just forget that aspect of this discussion :) from the measurements it seemed like they'd have to. It's raining too hard to drop the engine down in the bay and see where the arms are going to land so I started a discussion based on the measurements we'd made so far.

[mitchlevy7]

Doesn't compromise it by much, drivetrain come out very straight. A number of cars have logged over 100k on this forum, post swap, on all used parts, without premature drivetrain wear. Your idea is good, but why reinvent the wheel on this one? Probably over 100 swapped cars on the forum, that's a lot of success

Personally, I'd go with Akg poly swap mounts, perfect forint in my car, 60+ track days with no issues

AGREED +1. why mess with what what works?

even if you think using m5 mounts that happen to work is sketchy, theres mounts engineered for this swap that are proven just as much as the m5 mounts.

if you are thinking about balence in the car, maybe consider the aluminum 24v from the z3s.

[FredK]

1. The mounts serve to place studs further outboard than normal E30 engine mounts.

2. A reinforcement box could work to place the studs in the "correct" orientation, meaning, to shift the mounting points further outboard so weird combinations of engine mounts won't be required. However, there isn't sufficient room to do so. If you place a normal hydraulic engine mount in the inner hole of the engine mount ear on the subframe, you will see there is nearly no room to move it outwards towards the frame rail. Unless there is a different model hydraulic mount that has a smaller diameter, this won't work.

[ForcedFirebird]

No, the other mounts are used because the holes in the arms moved. Just an FIY, the m42 engine mounts will work on a 24v e30, just like the other mounts will replace the expensive flui filled m42 mounts.

You are over-engineering this and thinking too hard about it. It's real simple the way BMW did things. 4 valve per cylinder engines have a specific location for the mount holes, as well as engine angle - m42 and 24v's lean the same amount more than the m20 to save room after widening the head to make more room. This is why the g240 can be used on a 24v and the shifter doesn't need to be modified, whereas the g260 does.

And if you think there will be weight transfer, there will be, but due to leverage and the weight of the engine itself not moving, the COG will remain primarily in the same place, otherwise instead of moving engines back in the engine bay for race cars, they would simply have extremely long engine arms that extended into the trunk ;)

[smooth]

Unless there is a different model hydraulic mount that has a smaller diameter, this won't work.

thanks Fred. I was thinking of using my akg bolt through mounts from my e30.

one of the concerns we had was re-using the poly mounts on the tranny while using a rubber mount up front for the engine. we weren't sure if that would transfer too much vibration to the transmission.

Thanks forcedfirebird,
if what you're saying is true, then we won't gain much by moving the mounts forward. When we saw that the stock mount points for the arms could be moved forward a few of us started brainstorming about the impacts this might have for nose balance. maybe our measurements are off. it looked like the swap mounts moved the bolts aft and not outboard.

[328ijunkie]

+1 Why start moving stuff. BMW has thought this one through. For instance. 24v/ZF320 + STOCK ZF shift linkage = perfectly centered in E30 shifter hole.......
Food for thought.