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Old 10-12-2019, 09:15 PM   #1
Tfrasca
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Default Help me design motor mounts

Hey. I have functioning motor mounts that I made for my 142/OHC setup. They used the stock mounts and brackets on the subframe. Stock mounts allow for way too much movement, and since I'm putting a 16v in such a tight space, I can't have all that.

So, I'm making mounts out of torque rods. My dilemma right now is whether to bolt a bracket with tabs for the torque rod to the frame rail, or to weld tabs directly to the subframe.

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Ideally, I'd get the mounts up onto the frame rails, to get the mounting points as wide as possible. Also, being able to drop the subframe without supporting the engine would be neat. My concern is with drilling swiss cheesing my frame rail with four M10 holes. Will the front of my car snap off? The holes would be between the subframe bolts, so kind of a low stress area. (maybe?)

If that's a no-go, I could weld the tabs onto the subframe, but then the points aren't as wide and my engine is still on the subframe. I guess I could also weld the bracket directly to the frame rail, but I'm not sure how thick the frame is, and it might not be a good match for the 3/16 plate that the bracket is made out of.

Any input? If you've made it this far, I'm impressed. Nobody cares about 140s.
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Old 10-13-2019, 01:02 AM   #2
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Old 10-13-2019, 01:40 AM   #3
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If you want to bolt the engine mounts in, just use some m10 weld nuts and call it good. That’s more than enough to hold the engine in place.

https://www.mcmaster.com/90563a670
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Old 10-13-2019, 02:01 AM   #4
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Originally Posted by culberro View Post
If you want to bolt the engine mounts in, just use some m10 weld nuts and call it good. Thatís more than enough to hold the engine in place.

https://www.mcmaster.com/90563a670
Interesting, I've never seen those. I'll get some and mess around with them. Thanks.
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Old 10-13-2019, 02:03 AM   #5
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Originally Posted by Vincent Gagnon View Post
That looks great. Is that a later style torque rod, or something you made to accept a generic bushing? I have a set of early torque rods with smaller bushings than that. How were your mounts in terms of engine movement vs. NVH?
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Old 10-14-2019, 10:28 AM   #6
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I really can’t say anything about the structural integrity of the frame rail there but I would choose that over the subframe if you think it’s strong enough. With that style mount (same as what is on my 122), it’s a little more difficult to R&R the engine. Not impossible by far, just not as easy as factory mounts with a stud poking up. So if you need to drop the subframe in the future, it’s nice not to have to mess with the engine mounts. I had to do it once after welding a bung in my oil pan only to find out once I filled it with oil that it had a tiny pinhole leak.

After getting my engine back in a few months ago I’ve found that it’s easier to unbolt the mount from the engine block, get everything lined up well enough, and then thread the bolts back in.
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Old 10-14-2019, 12:26 PM   #7
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Good point. Iíll try to get the mounts off the crossmember.

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Originally Posted by AndrewNance View Post
I really canít say anything about the structural integrity of the frame rail there but I would choose that over the subframe if you think itís strong enough. With that style mount (same as what is on my 122), itís a little more difficult to R&R the engine. Not impossible by far, just not as easy as factory mounts with a stud poking up. So if you need to drop the subframe in the future, itís nice not to have to mess with the engine mounts. I had to do it once after welding a bung in my oil pan only to find out once I filled it with oil that it had a tiny pinhole leak.

After getting my engine back in a few months ago Iíve found that itís easier to unbolt the mount from the engine block, get everything lined up well enough, and then thread the bolts back in.
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Old 10-14-2019, 12:41 PM   #8
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When making the mounting tabs/ears, I found a few tricks to make engine installation easier:

On the mounting tabs, weld a thick washer to the bushing side. Then smooth out the weld to offer a nice transition as the motor mount slides in.
You can see what I'm talking about here: https://www.motorsport-tools.com/dur...scort-mk2.html
Here as well: http://grp4fabrications.com/product_...oducts_id=1286

When you weld the mounting tabs onto the base plate (or frame rail), use a thin washer between one side of the motor mount bushing and one of the plates. This will space the plates apart just enough to make installation easier. The mounting bolt will easily cinch the ears closed.

Lastly, if you rotate the mounting ears so they are angled slightly forward (looking horizontally and at the frame rail) the engine will slide into them easier. Most people use an engine hoist to install the engine (and trans too), when lowering the engine moves towards the firewall as well as down.
Visually, the mounts look like this: "/ /" , not like this "| |"
The angle doesn't have to be much. I've found that approx 3-5deg (or the top edge ~ 1/8" forward with a 2" tall mounting tab..) of tilt is the sweet spot.
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Old 10-14-2019, 06:47 PM   #9
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Quote:
Originally Posted by Tfrasca View Post
That looks great. Is that a later style torque rod, or something you made to accept a generic bushing? I have a set of early torque rods with smaller bushings than that. How were your mounts in terms of engine movement vs. NVH?
It's something I made with the help of John V. to accept a Ford Escort Mk2 Van front leafspring bushing.

The engine is really stable, but the vibration is fine, I mean, you feel the engine more than before but it's reasonnable for a daily driver.

If you need more details, there is a good thread here:

https://www.rallyanarchy.com/phorum/read.php?1,52039

Keep us posted.
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Old 10-15-2019, 01:19 AM   #10
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Quote:
Originally Posted by culberro View Post
When making the mounting tabs/ears, I found a few tricks to make engine installation easier:

On the mounting tabs, weld a thick washer to the bushing side. Then smooth out the weld to offer a nice transition as the motor mount slides in.
You can see what I'm talking about here: https://www.motorsport-tools.com/dur...scort-mk2.html
Here as well: http://grp4fabrications.com/product_...oducts_id=1286

When you weld the mounting tabs onto the base plate (or frame rail), use a thin washer between one side of the motor mount bushing and one of the plates. This will space the plates apart just enough to make installation easier. The mounting bolt will easily cinch the ears closed.

Lastly, if you rotate the mounting ears so they are angled slightly forward (looking horizontally and at the frame rail) the engine will slide into them easier. Most people use an engine hoist to install the engine (and trans too), when lowering the engine moves towards the firewall as well as down.
Visually, the mounts look like this: "/ /" , not like this "| |"
The angle doesn't have to be much. I've found that approx 3-5deg (or the top edge ~ 1/8" forward with a 2" tall mounting tab..) of tilt is the sweet spot.
I wish I'd read this before I welded up the receiving end of the bracket. I didn't include a washer or angle the tabs slightly. I haven't been able to put an engine and trans into this car together, though. I drop the trans off the bell housing, then pull the engine and bell housing. Hopefully this mount won't be too big of a hassle. Having the bracket bolted instead of welded to the frame rail will also help.
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Old 10-15-2019, 01:26 AM   #11
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Quote:
Originally Posted by Vincent Gagnon View Post
It's something I made with the help of John V. to accept a Ford Escort Mk2 Van front leafspring bushing.

The engine is really stable, but the vibration is fine, I mean, you feel the engine more than before but it's reasonnable for a daily driver.

If you need more details, there is a good thread here:

https://www.rallyanarchy.com/phorum/read.php?1,52039

Keep us posted.
That's a good thread. I stumbled upon that one before I decided to make these mounts. I got some stuff welded this evening. This is where the passenger side mount is right now:



The bracket will bolt to the frame rail in some manner. I like the idea of weld nuts, but I'm not sure I'll be able to get in there to weld them unless I pull the engine, and I want to keep my old block in there while I get everything mocked up and the new block is getting built.

Also, my little MIG struggles with the 3/16 steel. I'm going to add a triangular gusset between the torque rod and the plate on the block, so maybe the added structure will make up for less than ideal weld penetration...

Last edited by Tfrasca; 10-16-2019 at 10:41 AM..
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Old 10-15-2019, 01:51 PM   #12
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Quote:
Originally Posted by Tfrasca View Post

The bracket will bolt to the frame rail in some manner. I like the idea of weld nuts, but I'm not sure I'll be able to get in there to weld them unless I pull the engine, and I want to hang keep my old block in there while I get everything mocked up and the new block is getting built.

Also, my little MIG struggles with the 3/16 steel. I'm going to add a triangular gusset between the torque rod and the plate on the block, so maybe the added structure will make up for less than ideal weld penetration...
Looks good so far!

If you can get the metal squirt gun even remotely close to positioned, you can "stitch" the weld nuts in, just one large tack weld at a time. The flange is probably just 2mm thick, so they don't take much heat. I've installed them into some seriously tight spots with this method.

For better penetration, bevel the tabs and tube. A 110v welding setup should be able to do 1/4" in a single pass without any issues.
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Old 10-15-2019, 02:05 PM   #13
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Originally Posted by culberro View Post
Looks good so far!

If you can get the metal squirt gun even remotely close to positioned, you can "stitch" the weld nuts in, just one large tack weld at a time. The flange is probably just 2mm thick, so they don't take much heat. I've installed them into some seriously tight spots with this method.

For better penetration, bevel the tabs and tube. A 110v welding setup should be able to do 1/4" in a single pass without any issues.
So for the weld nuts, the flange ends up proud of the surface of the frame rail? Then grind down any extra protrusion from the racks?

I put a bevel on the torque rod and it welded much better. Iíve done that in the past but totally forgot to do it for the bracket. I think itíll be ok though.
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Old 10-15-2019, 02:21 PM   #14
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So for the weld nuts, the flange ends up proud of the surface of the frame rail? Then grind down any extra protrusion from the racks?
Correct. The flange is about the thickness of a washer, so probably closer to 1-1.5mm. If you keep the torch pointed more towards the frame rail, and then move the weld puddle into the flange of the weld-nut, you'll have more success and a lot less (no) grinding to do.
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Old 10-15-2019, 04:07 PM   #15
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So for the weld nuts, the flange ends up proud of the surface of the frame rail? Then grind down any extra protrusion from the racks?

I put a bevel on the torque rod and it welded much better. Iíve done that in the past but totally forgot to do it for the bracket. I think itíll be ok though.
no bevel... I'd say to do it again. I just had a couple issues with brackets cracking welds. I welded both sides, but forgot to bevel and ended up cracking welds. It was a sway bar bracket, so it saw more forces, but still. I wouldnt risk it, and I wont ever again.

Also, chase all your nuts after they're cool.
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