Does anyone sell swap plates or modify 320i subframe for the m20

**gregg7230** · 03-21-2016, 10:16 AM

Hey forums, I'm looking at a 2.7l stroker. Does anyone sell swap plates or modify the front subframe to accept the m20? Can't find a 6 cylinder subframe. Any ideas or direction will also help. I remember Charbel had fabbed his own mounts but I'll also need a suitable subframe. I'm not good at making parts, I'd much rather pay for the part or pay someone to do it. Thanks guys

**bassboy3313** · 03-21-2016, 10:39 AM

Best bet would probably be to mock fit the m20 into your car with your stock m10 subframe and make cardboard templates of the engine mount arms needed. Then you can take your subframe and templates to a welding shop and have them weld it up for you. Otherwise you can look at bmwe21.net and possibly find an e21 m20 subframe and arms. Getting harder and harder these days tho. Also, quick google search found me this ... http://www.hikfabrication.com/arvixe/E21_products.html Not sure on availability tho.

**gregg7230** · 03-21-2016, 02:23 PM

Thanks brother! I have no idea how you found that, but that's why I come here. If anyone else has any other suggestions or buy locations it'll be appreciated.

**Tom D** · 03-21-2016, 07:21 PM

Originally Posted by bassboy3313

.....http://www.hikfabrication.com/arvixe/E21_products.html ....

I would definitely not do this! if bmw thought it was sound engineering practice to attach the M20 to the M10's mounting points then they would have only made one subframe. to hang a torquey six cylinder off that lever on the driver's side is looking for trouble. just modify the M10 frame and use the E30's mounting arms.

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here is the M10 subframe, it happens to be post 9/78 production.

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and here are the pre and post M20 subframes

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the above are all factory E21 subframes to be used with E21 engine mounting arms. if you use E30 mounting arms then the E21 factory M20 subframe still needs modification because the mounting perches are too far forward.

the best way to do this swap is to fabricate some new perches and have them welded onto the M10 subframe. by using the E30 arms, which are really nice, as well as available, it puts the motor mount right next to the bolt that hold the subframe to the frame.

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scroll down the page a little bit, you'll see what I'm talking about. http://www.bimmerforums.com/forum/sh...t#post23450393

**gregg7230** · 03-21-2016, 08:24 PM

Thanks Tom that'll help ALOT. It seems like it's an easy fix for a machine shop and or welder. Thanks again.

**DougIng** · 03-21-2016, 09:41 PM

I like what Tom said too. The limiting factor here are the 323 motor mount arms. They are NLA but E30 arms are easy to get. The rubber motor mounts are virtually identical. You should be able to reinforce the subframe with gussets.

**Layne** · 03-22-2016, 12:55 AM

Originally Posted by Tom D

I would definitely not do this! if bmw thought it was sound engineering practice to attach the M20 to the M10's mounting points then they would have only made one subframe. to hang a torquey six cylinder off that lever on the driver's side is looking for trouble.

I don't like the design of those arms for sale, but I strongly disagree with this statement. BMW did not design the car and both engines to work together, they designed the car around one previously existing engine, then designed another engine for the car. Most likely both setups involved compromises. All subsequent BMW's have used the same subframe for all engine options. The stock M10 mounts are pretty soft, but there's no reason to think the mounting location is inferior in any way. No one has ever had any problem building M10's that far exceed stock M20 power and torque. My personal preference would be to fabricate new arms when swapping any engine into any chassis, but it makes no real difference if you modify the subframe or the arms. I would never use a tubular design though, I'd make a 4 sided box similar to the stock E30 M20 arms.

**jjgbmw323** · 03-22-2016, 06:12 AM

I agree with Layne. I think the design of the arms should be stronger not tubular. I also have a set of 323i arm 78 arms, old style, you could take these to a machine shop and make copies.

**gregg7230** · 03-22-2016, 06:55 AM

That sounds great how would we coordinate that? Also if I copy your arms, would I still need to modify the subframe? Or will it sit in with the 323 arms?

**Layne** · 03-22-2016, 11:14 AM

Originally Posted by gregg7230

That sounds great how would we coordinate that? Also if I copy your arms, would I still need to modify the subframe? Or will it sit in with the 323 arms?

You would still need an M20 subframe, or a fabricated copy of one. That's not really a useful avenue to pursue since it would require both items to be fabricated when you really only need one or the other.

**JGee86** · 08-07-2016, 01:15 AM

[QUOTE... http://www.hikfabrication.com Not sure on availability tho.[/QUOTE]

These are certainly still available. I got to say even though it's obvious, I don't understand why anybody would think these arms are weak sauce. I don't put anything out there that I don't believe in, period I personally guarantee customer satisfaction. Send them back in paintable condition and get a full refund. I would like pictures and reasons why they don't work for you, but not mandatory.

They are made out of 1.75" 0.120 wall DOM tube, "roll cage material", the plate is 3/16". How are these arms the weak link between the sub frame, motor mount, and the engine block for that matter? The long "horn" on the sub frame gets cut down substantially (see template below). That template moves the original holes then you cut off the excess. Making the sub frame stronger, but stronger than these arms? The complete modification can all be done from the top side with the engine removed; which means NO sub-frame, steering rack, control arm, etc. removal required.

I developed these arms for a member here ryane21euro through a shop in HB so I don't know him personally. He wanted a M20 swap but, the 323 sub-frame and shipping was too much money. I came up with a solution that eliminated the need for both the sub-frame and the different arms.

Ryanes Car

The tab at the end of the stock arm appears to be the weakest point between the two designs to me, given the way the motor exerts force on them.

JH

**rabobian** · 08-09-2016, 07:44 AM

Try this guy out too. He does a lot of custom fabrication. He does not show an engine mount for the M20 to M10 subframe but it would not surprise me if he either has some or can make some.

http://www.classicdaily.net/

**Layne** · 08-09-2016, 10:20 AM

Originally Posted by JGee86

[QUOTE... http://www.hikfabrication.com/arvixe/E21_products.htmlI got to say even though it's obvious, I don't understand why anybody would think these arms are weak sauce. I don't put anything out there that I don't believe in, period I personally guarantee customer satisfaction. Send them back in paintable condition and get a full refund.

Props for offering a much needed, small volume, probably not very profitable part, and for standing behind it. I don't think they're weak sauce, or that they're definitely going to break in the car. But if you put it on a testing machine and pushed it until failure, the weld between the tube and the plate would rip. That point has far less strength than the rest of the part. BMW's part would have to buckle like a failed crane boom, and would probably take 5 times the force to do that. It's far more likely to stress crack than to buckle. If you redesigned your part into a box shape, obviously the price would have to go up and you might lose some of an already tiny market. All I was saying is that if I built one set for my own use, they would be shaped like the original ones.

**JGee86** · 08-13-2016, 01:00 PM

Originally Posted by Layne

Props for offering a much needed, small volume, probably not very profitable part, and for standing behind it. I don't think they're weak sauce, or that they're definitely going to break in the car. But if you put it on a testing machine and pushed it until failure, the weld between the tube and the plate would rip. That point has far less strength than the rest of the part. BMW's part would have to buckle like a failed crane boom, and would probably take 5 times the force to do that. It's far more likely to stress crack than to buckle. If you redesigned your part into a box shape, obviously the price would have to go up and you might lose some of an already tiny market. All I was saying is that if I built one set for my own use, they would be shaped like the original ones.

Thanks, but I must disagree, looks more likely to me that the tab on the end of the stock piece would fail first but after the motor mount and sub frame. I would love to test them both but, I don't even want to know how much that costs.

If anybody wants to do a full review on these mounts, I will offer a $50 rebate.

**hooligan762** · 01-24-2019, 04:02 PM

Reviving the thread. Messaged JGee86 and these are available. If we can pull together 9 more people, the price is $160 shipped, which is a great price and huge time saver!

From JGee86:

"If you can get a group buy going. I'll do a set of ten for $160 each shipped. (2-3 week lead)"

I'll start.
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