Engine mount

[decoupe]

In the process of modifying my accelerator linkage, I found a crack on the driver side engine mount starting at the leading edge and spreading through the lower bolt hole and more than half way across the face.

When viewed on edge, the mount has a 1/4" deflection below the lower bolt hole. Is this part of the design - I assume so or I'm producing a lot more torque than the original engine did.

I'm somewhat surprised at the failure given the thickness of the material and OEM rubber bushing (as opposed to urethane). As the part is no longer available I'll probably weld the crack and gusset the mount with some plate to create a right angle connection at the leading edge. As this is curved when viewed "face on" this won't be easy.

Any other suggestions?

Doug

 

[Luis A.]

That's impressive. How much power are you running. Still, I'll let the experts chime in as to whether any amount of sub-Veyron HP can do this to that beefy piece of steel. Or would other weaker points of the drivetrain go first?

What makes you say the part is NLA? I see in stock at Penske and Tischer. $30.32 minus the discount nets you under $25.

 

[Sven]

Doug,

The mounting surface with the 4 bolt holes should be perfectly flat, not curved like your piece. You could always pound it flat and then weld the crack from both sides. A good welder should be able to take care of it.

Maybe the engine was lifted out by PO incorrectly causing the tab to bend, or the right side mount came loose allowing the engine to twist on the left bracket, or the engine dropped?

 

[deQuincey]

obviously this is only my opinion

but I do not think that this is due to torque increase nor to bad assembly / bad engine handling in the workshop

I think it can be a fatigue issue, good you saw it before it cracks all the width long

I would repair it with a proper welding and if possible i would add a couple of ribs as a reinforcement, or i would weld a thin steel plate all over and redo the holes and use longer bolts to compensate the thickness increase

 

[decoupe]

That's impressive. How much power are you running. Still, I'll let the experts chime in as to whether any amount of sub-Veyron HP can do this to that beefy piece of steel. Or would other weaker points of the drivetrain go first?

What makes you say the part is NLA? I see in stock at Penske and Tischer. $30.32 minus the discount nets you under $25.

LuisA et al,

Thanks for the tip on availability. REAL OEM showed it as "ended" so I took that as no longer available. I'll have a look around to see what I can find but I'll still gusset the mount. I was being facetious on the torque - probably just 40 years of fatigue.

The 1/4" deflection is disturbing and means reassembly will have some challenges. Better check the other mount to see what's there.

As usual - thanks to all,

Doug

 

[61porsche]

Cracked left motor mount

Doug,

I suggest you change it out rather than try to weld it back up, even with a corner gusset. Chances are the metal will just tear again and in my humble opinion isn't worth taking a chance on what could happen. If I absolutely had to repair it would be tigged.

The parts diagram does indicate to me that there is a slight bend past the bottom bolts. That's what I remember from last week when I was repairing the ball stud on the linkage plate which was slightly loose.

I would replace the rubber mounts as well on the chance that yours might have streached. The uerathane mounts have been known to tear unless you know for sure it has a built in restraint. ( some do, some don't)

Question for the gruppe: Does anyone have the original restraints still left on their car? It looks like they just restrain the rubber mount from seperation.

 

[Peter Coomaraswamy]

Might look like this

Are these the restraints you mean? (attached to the sub-frame in front of where the rubber mounts go)?

 

[61porsche]

Motor Mount Restraints

Yes, those are the ones. Thanks for posting since most are long gone by now.

 

[decoupe]

With respect to the repair and gusset approach, I'll do that for practise and then replace it with a new mount (but add the gusset as well) before everything goes back together.

I was wondering about the stops that are shown in the parts schematic but are missing on my car - that would possibly explain the metal fatigue and subsequent cracking. If all they did was protect the bushing from tearing instead of stoping the forward motion of the mount/engine under extreme braking they are not much good. Given the minimal clearance to the radiator from my viscous fan, there are lots of good reasons why this would be worth adding. Another one for the list. Long list.

Doug

 

[Peter Coomaraswamy]

I'll be at the cave tonight

I will take some pics with a ruler/etc. in case someone wants to make some- they don't look too difficult to manufacture. I'll post them later tonight or tomorrow- hope it helps

 

[Peter Coomaraswamy]

Here are some pics- I hope they're helpful

Mount restraints

 

[decoupe]

Thanks Peter - looks like an easy enough item to copy.