Sierra cast alu engine mounts
 

To make a long story short, I had clearance problem while doing my steering column extension. Using the Sierra rubber engine mount (80mm high), the extension would touch the the cast mount, using the Land rover mounts (35mm high), the extension would touch the water pump outlet.

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To solve the problem, I needed 63mm hight rubber mounts. I found these neat (and stiff) Volvo mounts, 48mm high, and I made a small 15mm extension to reach the right height.

I'm quite happy with the result, I got the clearance I needed under the water pump and above the cast mounts.

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Problem : the threaded rod on the Volvo mount is too short to go all the way through the cast aluminium engine mounts from the Sierra's DOHC. The body of the mounts is hollow, but the drilled part is full. So I “machined” them myself. I removed about 15mm of thickness, and it is now about 15mm thick.

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I really would like to leave them like that, but I don't want my engine mounts to brake. What do you think? Is it too weak to your opinion, or will it support the stress of the engine movements?

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All opinions, input and advises are welcome :)

Thank you.

I personally would have just ditched the cast mounts and fabricated new ones from 30x30x3mm or 40x40x3mm box section and plate, but then thats my answer to every thing if it doesn't fit don't spend money on it just make one.
The only problem I can see with your cast part is that where you now have a 90' machined cut at the bottom this is where it will most likely break in the corner. I would have removed most of the material with the end mill then done the last section with a bull nose cutter to give a 5-10mm rad so there would be less of a stress point.
All you can do is run it and see what happens you may get away with it for awhile or may never break only time will tell.

Make some new ones it will pay dividends in the end as I think you will find the engine rocking about in the engine bay and the mounts are a potential failure point.

Thank you guys for the replies.

I totally understand your points, and you are right. I had the pre-feeling something was not completely right when I did them, and again, a post on this forum is putting me back on the right track :)

I will definitely try to make new ones. It will have the other advantage for me to accurately chose the height and get rid of these small 15mm steel extensions cylinders I built and I'm not found of either.

Keep you posted.

Thanks again.

Rather than buying 30x30 box section tube, and removing my "book" engine boxes, I have tried to "copy" the cast aluminium engine mount wit 25x25 tubes. I could adjust their vertical position on the 5mm plate attached to the engine in order to get rid of the 15mm extension cylinder I did in the first place. I will cap the end of the tubes to close them.

Attachment 1664

It fits perfectly, I have the right height and the clearance I needed between the steering column and the water outlet. For now, the elements are just tacked together, and before fully welding them I wanted your opinion. Will it be strong enough?

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I will also add 2 plated, on top and on the bottom, to "close" and brace the triangle. The bolt is just here to hold them together, and will be removed after I weld the plates. It will be a water drain as I don't want any water to be stuck in between the two plates.

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Please tell me what you think, is it OK, shall I fully weld and put the plates on top. If you confirm it is OK, I'll do the right mount in the same way.

Thank you very much in advance.

I'd think that bottom plate is too thin, I'll be doing mine out of 6mm plate...

btm plate DEFO too thin......agree a minimum of 6mm plate

I'm also going to use some 40mm box section which is 4mm wall I think. not sure if your box section is thick enough, also it's not welded all round, can you not construct it in such a way that you weld around the whole end of the box section rather than just one side?

Thank you for the replies.
I changed the bottom plate to a 6mm (actually 5.5mm!) plat.I also made it longer, and it looks stronger now. Thanks for the tip.

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I also cut another top plate which will cover the full length of the mount. I think it makes more sense.

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JPS, I totally understand you last point, that makes sense. This was my first idea too, but while drawing, I discover that it would give a "pointy head" to the triangle, and the contact surface with the bottom plate would be to small. But now, with this longer and thicker bottom plate, it would be definitely a better option. But honestly, if you guys think that this version is OK and will be string enough, I'll leave it like that. Just let me know!

Thank you for your inputs.

Possibley too late but I placed the mounting plates where the rubbers go on the chassis legs, and the angle of the load is more acceptable instead of being 90 deg/ vertical on the plate close to the engine.

Thank you Paul.
Yes, I know. The best thing would have been to do a custom engine mount as described in the book (alternative engine mounts), without using the boxes made with the "EM plates". I totally agree that angled legs would have been better. But I made the "boxes" and they are fully welded to the chassis, because I didn't expect I would have clearance issues between the water outlet and the steering column. I really didn't want to remove them, that is the reason why I "copied" the original cast mounts, and just adjust the height to solve the clearance problem.

The engine mounts are now finished. They look like that.

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I braced the right one with triangular plates on top. The bottom plate (6mm) is fully welded on the full length of the tubes making the "skeleton" of the mount.

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No bracing on the right mounts, but two plates, fully welded to the tubes, on top and at the bottom.

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I hope they are going to be strong enough. To me, they do look strong enough, but again, I'm not a specialist. What do you guys think of the final mounts?

Any comment is still welcome.

Thanks a lot.

I thought it would be too late but was worth comment I thought,I have one box and one on the chassis on my frame more by bad management than forethought.

your latest versions look tough enough so would not worry.

Look at the mass of the ally ones and think of the amount of metal used to hold up the motor just because its alloy,so yours should have no problem.

Thank you for that, very helpful and reassuring. Hope I will sleep better this night than last night :)

I agree with you on comparing the amount of metal with the original ones.

Now I just hope it is going to be OK for the SFRO (Swedish IVA) inspector too!

Thanks again.

I hope so too,over engineered is always better to me.

Good luck.