Thread: Fabricating Engine Mounts

That $100 will save a lot of effort. If you do make your own mounts, just make sure that they attach somehow to the top and bottom flange edges somehow and not just the chassis sides otherwise the chassis will flex and crack and the engine will fall out. IF you're not sure, then plate the side of the chassis. Also, remember that you can't weld the top and bottom flanges on the chassis for engineering (cracking) reasons, despite the factory doing this.

Originally Posted by Slunnie

That $100 will save a lot of effort. If you do make your own mounts, just make sure that they attach somehow to the top and bottom flange edges somehow and not just the chassis sides otherwise the chassis will flex and crack and the engine will fall out. IF you're not sure, then plate the side of the chassis. Also, remember that you can't weld the top and bottom flanges on the chassis for engineering (cracking) reasons, despite the factory doing this.

Thanks Slunnie. I'm just not sure I understand part of what you said. What exactly do you mean by the "flange" edges. Also, if they can't be welded but must be attached, how is this done?

They can be welded on BUT they need to be done by a Certified welder.

IF the welding is not done correctly the vibrations from the motor will cause fatique cracks around the welds and the the motors "torquing" action when you plant the noisey boot will tear them from the chassis.

Im not sure what Slunnie means when he says you cant weld the flanges on a rover as they are a box section chassis and dont have flanges, thats more to do with the C section chassis so far as Im aware.

However I do agree with plating up the inside edge of the chassis if your putting new mounts on for a different engine as I have seen a few change overs done on the series rovers where the weld has looked good but the process of welding has been near an internal rust point on the chassis and has caused a failure there in short order.

Sorry, when I said flanges I mean the top and bottom faces of the box section chassis. These are the parts of the chassis that take the stress and strain, where the sides keep them seperated. You can weld till your hearts contented on the sides and it's not a problem, but the rules/regulations on chassis modifications in NSW at least are that the top and bottom of the chassis should not be welded on to.

There is some text here from the RTA regarding engine changes and welding chassis between pages 2&4

http://www.rta.nsw.gov.au/registrati...s_nov_2007.pdf

You can see in this picture for example how the outrigger wasnt manufactured to meet the very top and the very bottom of the chassis and the resultant flex in the side of the chassis has ended up cracking. In this particular case it was a companion tanks that had one half swung off it and had only been installed for 1 year and about 17,000km. I've seen these actually completely break off.


All heavy mounts will meet the top and bottom of the chassis, and for extra strength they will add a reinforcing lip along the edge of the mount like on a coil spring perch to make sure the mount doesn't also tear - it's like another flange. You can see it on either side of this spring perch.




Actually, this is a good example. These are LandRover Series 3 Stage 1 V8 engine mounts that are attached to the top flange (plate) of the chassis quite well which increases significantly the strength and the drop all the way down to the bottom of the chassis with the angle of the sides providing stiffness for the sides of the chassis to prevent cracking in that area.



The top plate thats actually on the top of the chassis is also there to prevent any fore/aft flex in the mount from driving/braking forces and to stop cracking in that direction.