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Discussion Starter #1
I have a new problem. Was about to replace my brackets that mount the AC and alternator, and figured before I put those back on, it's a good time to remotely relocate the oil filter. However, while doing that, it turns out that my engine mount on the passenger side is cracked.

Here's a photo of the cracked mount, clean all the way through.
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Anyways, I guess I have a choice. I can either have the shop send me new mounts, or see if I can replace it with something better and would like to hear suggestions. The problem is, I don't know why this has happened so having the mounts replaced with the same doesn't sit well.

Comments, suggestions much appreciated.
 

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I've only seen that type of engine mount used for marine or stationary engines etc. It looks like there is very little room for a compression (shock) load. When it bottoms out all that load is transmitted to the top mount which is located on a tab with very little support. I would cut off the broken tab and weld on the new one with more support to the rear. How thick is the steel mount?
 

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As was mentioned, that style mount was mainly on marine applications. One thing I don't see are any triangular braces welded into the corners of your brackets. Even though you appear to have very thick metal, an 800 lb engine bouncing around on it is going to make it flex. The most common mount most use is the LORD's fluid type which seem to handle the engine's vibration much better. Also, marine engines typically had a fluid balancer mounted on the the front of the crank to help control vibration. Here's a photo of the LORD mount and an install.
 

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Discussion Starter #5
I was thinking of doing this work, but now I'm concerned on the current placement of these mounts and the amount of load they bear, especially as I was trying to match Lord mount ratings. I'm inclined to find someone that has experience and can better judge this setup.

Which leads me to wonder if I'll have to pull the engine and if this project will ever finish.

If anyone can suggest shops in Texas that have experience with 4bt mounts, much appreciated.
 

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In Texas I would find a GOOD oil patch machine/weld shop and have them make them, those shops are familiar with doing odd work and their own engineering If your alignment is good where it is have them just do one side at a time with it sitting in place.........$.02
 

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Discussion Starter #7
Thanks eggma918. My problem is I'm not sure that that alignment is good. All the weight sits on the back tip of that top mount and the bolts on that top mount are several inches (at least 5" IIRC) forward to where it bolts on the block. I'll have to go back and measure that. So in no way are the supports where it bolts on the block and weld to the frame in alignment (meaning above and below each other).
 

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Yes, it looks like your bolt to the top of your mount is right near the edge of the block bracket. That is probably putting a lot of stress at that point. Are you using the mid mount point on the engine block or the front ones? Unless you have an obstruction, it would have been better to extend that top plate a bit farther and brace it with some welded in angles. Ideally, you want the center point of the motor mount to be in the center of the brackets, but sometimes that doesn't fit the install.
 

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I ran a similar set up in my jk but used the factory first gen square mounts and never had an issue, where are you located in tx?
 

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Discussion Starter #10
Houston. You don't happen to have a photo of those, do you? I haven't settled on a solution yet, still trying to put a plan together.
 

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Looks like you are getting a load/vibration concentration right at that mounting hole. Simplest fix would be to grind out the crack, weld it back up, weld a 1/4" patch plate to the top side of the broken area, and for good measure I'd add a gusset between that horizontal member and the vertical member that is bolted to the engine. Make the patch plate with just a hole, not a slot, and debur and gently radius the sharp edges of the hole and slot to eliminate stress risers.

My guess is that the vibration of the 4BT is more the culprit than the weight. My motor mounts have no material thicker than 1/4", and the tube is 1/8" 4130. It's holding up a 6BT and has spent plenty of time off-road, and shows no signs of cracking or other failure.







 
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