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Old 11-27-2016, 12:55 PM   #1
cheff
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E30 B35 Swap Issue: Compressed M20 Engine Mounts

Hey everyone,

I am seeing an issue with my B35 swap and wanted to see if anyone else had the same issue. I completed a B35 swap a few years back and have been overseas with my E30 up on blocks in storage while I was gone for 4 years. I got back and upon a thorough inspection (while looking at the steering rack I need to replace,) I noticed that the engine mounts had compressed significantly and the oil pan was resting on the subframe.

Has anyone seen this with their swap? Is there an issue with the weight of the M30 engine on the M20 mounts. I didn't think there was such a HUGE difference in weight that this would be an issue. Not to mention that everywhere I look on forums I see people using the M20 mounts.

I am trying to determine the best option moving forward, as I don't want this to happen again or have the engine start hitting the subframe while driving.

Options as I see it:

1) Continue using the already compressed mounts and either make or buy spacers (such as the ones sold at: Condor Speed Shop https://www.condorspeedshop.com/prod...gine-riser-kit )

2) Swap out the M20 mounts for another stiffer mount (possibly the E34 M30 mounts.) I have been trying to see what the thickness is between the M20 and M30 mounts, but have had little success. It looks like the M20 mounts are nominally 50mm thick, but I haven't been able to figure out the M30 mount thickness? Does anyone know if these are interchangeable?

3) Any other recommendations?


Details:
'89 E30 Cabrio Chassis
'91 E34 B35 engine
I'm using the commonly available and used mounts at position 3.
Completed this around 5 years ago, only got to drive for about 3 months before I went overseas, so it has been sitting for most of the time since. Drove great with about 10mm clearance when installed (if I can recall correctly)

I am currently leaning at just putting in the spacers initially, but was looking to see if anyone has seen this after a while with their swap.

Thanks,

Alex
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Old 11-27-2016, 01:53 PM   #2
Anthony B
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Can't say I've seen my m20 mounts compressed, I am switching to condor bushings though as I find the oem m20 mounts move quiet a bit
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Old 11-27-2016, 02:03 PM   #3
e30davie
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How does an engine mount even compress? Are they fluid filled and all the fluid has leaked out? Seems rather odd.

If they have indeed compressed if just swap out with some other oem ones.
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Old 11-27-2016, 04:25 PM   #4
cheff
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With Picture

I have attached a picture, and also measured the thickness. So it looks like it is about 43mm high on the short side and 46mm on the longer side (which is certainly less than the number I recalled being the spacing above the subframe, maybe it was only 5 mm or so about. It looks like this has compressed about 6mm on average, if the 50mm number I found was correct.

I was also surprised that this would have "settled" so much over this duration of sitting. Maybe it has only compressed a couple mm more (which in this swap is everything.) It might be best to just put a small spacer (don't need the 20mm, but I can quickly fab something.)
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Old 11-27-2016, 04:47 PM   #5
TimeMachinE30
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I did what Alpina did when they put this motor and chassis together and used their mounts. I can get the part number if youd like. They are e34 mounts I believe.

Why that happened, is weird and I dont have a good idea.
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Old 11-28-2016, 07:19 AM   #6
cheff
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Quote:
Originally Posted by TimeMachinE30 View Post
I did what Alpina did when they put this motor and chassis together and used their mounts. I can get the part number if youd like. They are e34 mounts I believe.

Why that happened, is weird and I dont have a good idea.
If you have it handy that would be awesome. I can also do some digging around today and look for them when I get home from work. Thanks for the feedback!

Best regards,

Alex
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Old 12-01-2016, 03:20 AM   #7
lukeADE335i
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The M20 mounts do compress, even with an M20 there, but normally over a very long period of time. If they get oily they do soften up quicker (although yours look perfectly dry there - the arms you've used seem to be putting some sideways pressure on the rubber mount?).

Were the mounts new, what brand were they? I could see cheap mounts doing that more quickly than OEM.

I used new febi / bilstein engine mounts and they haven't been a problem - I'd just throw in some new, quality brand M20 mounts and be done with it.
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Old 12-04-2016, 09:17 PM   #8
cheff
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Thanks for the tips. I seems like sourcing some new and potentially higher quality M20 mounts is the way to go. I appreciate all of the feedback! Looking forward to getting her back on the road.

Cheers!
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Old 12-04-2016, 09:44 PM   #9
george graves
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Yea, my m20 mounts on my e30m30 squashed very quickly. You can stack some washers in a pinch. It seems once they compress so far, they stop after a while, but it's a cheap part to keep a spare handy.

What you don't want is the oil pan getting crunched. The pan to subframe clearance is kinda slim.
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Old 12-05-2016, 03:49 AM   #10
TimeMachinE30
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Quote:
Originally Posted by cheff View Post
If you have it handy that would be awesome. I can also do some digging around today and look for them when I get home from work. Thanks for the feedback!

Best regards,

Alex

Check my build thread.
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Old 12-06-2016, 09:46 AM   #11
Mr. Burns
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I'm very happy with my G-Man the Visionary mounts.
not sure if he still makes them, but have held up perfectly on my swap, PLUS you're supporting a forum member!
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Old 12-06-2016, 11:39 AM   #12
Bearmw
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I used Revshift M20 mounts on my B35 and have had no issue with them so far. The ones I got are blue but when I just checked their site they don't have that color anymore. I think the ones I got are rated 80A.
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Old 12-12-2016, 05:20 PM   #13
CorvallisBMW
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I'm very happy with my G-Man the Visionary mounts.
not sure if he still makes them, but have held up perfectly on my swap, PLUS you're supporting a forum member!
This. Swapped my m20 mounts for G-Man's poly mounts and absolutely love them. Zero increase in NVH, but better motion control and they should last forever.
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Old 03-15-2017, 09:02 AM   #14
Julto
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Someone tried M5 green mount ?
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