Lower Engine Mount

[timstemi16 0]

Basically i have a mi16 engine in the car with a group n bush and the rear lower engine mount keeps snapping at the welds.

Does anyone make a strengthened one or would anything else sort this problem?

[ORB 227 1 Cars]

Are you using a lengthened arm?

[timstemi16 0]

No standard arm.

Engine mount has a group n mount and arm has a white plastic bush in it.

[welshpug 1,657]

Is this the same part or a replacement breaking?

[timstemi16 0]

Yes same part breaking. Im wondering if the nylon type bush in the fork is possibly too hard?

Its an AB motorsport one.

[welshpug 1,657]

Find a better welder...

[timstemi16 0]

Funny you say that. Im a class 1 coded welder anyway...

[rallysteve 22]

A useful comment there Welshpug..

 

Which welds do you keep breaking, are they the ones which join the two sides of the fork together? If so it should be easy enough to gusset/fill in the mount fork with a couple of pieces of plate to move the load path away from the welds in question. If you are a qualified welder it should be a quick job to re-enforce the fork slightly.

 

Steve

[welshpug 1,657]

A useful comment there Welshpug..

 

it was a serious comment, I've welded a V6 lower fork, which is subject to 200 lbft, I am not coded, never had any lessons, it never broke.

 

it had a solid nylon insert too.

[Anthony 1,003]

If it's an otherwise standard fork, I think that I'd personally just get hold of another one that hasn't been previously welded and swap the nylon bush over.

 

Certainly it shouldn't be snapping and the combination that you're using has been used by a fair few people on track day and competition cars, and I haven't heard of anyone complaining of the fork snapping, let alone repeatedly. I've seen several cars that have been heavily front ended and the fork has survived (if a little bent) when everything around it has broken, so it's not a fundemental weak point.

 

What type and condition are the upper engine and gearbox mounts (and buffers for that matter)? Obviously with a solid nylon bush there's basically no give in the lower fork, so if the engine is moving around owing to the other two mounts then it's liable to eventually fatigue and crack the fork at the weakest point, which is likely where you've welded it.

 

It shouldn't be hard to strengthen it considerably, but personally I'd prefer to eliminate the source of the problem if at all possible rather than move the issue along to the next weakest link in the chain.

[timstemi16 0]

Other two mounts are standard new items. Engine doesnt move excessively at all though, couldnt handle the vibrations after using all group n mounts.

As Antony said it would just be good to get to the bottom of it.

Its been fine for years and all of a sudden twice...

Recently it has been mapped and putting out better power but isnt putting out huge torque, around 160 ft lb.

Only other things changed are front suspension and driveshafts. These items i dont think would contribute to the problem though..

It would be easy to strengthen the fork however, as mentioned that is then only going to stress bolts subframe and so on....