OK this is an unusual question but it's a thought I had.

If you had a valuable block with screwed up, or bad/damaged, motor mount pads, I know you can rig up a front motor mount plate.

What about welding a flat plate, say 4" x 4", on each side of the block, IN ANY NEW SPOT YOU DESIRE, to use "conventional-style" mounts (Mopar, Chevy, Ford).

Welding a small steel plate to the outside of a cast iron block should not produce stress that would make any difference in operation.
(This would also work with an aluminum plate welded to an aluminum block.)

For those who would prefer side mounts rather than a front motor plate.

What opinions are out there ? Why might this not work ?

I'm having a hard time imagining how this would ever be easier/better than repairing the original mount bosses.

I would be worried about different expansion rates of steel alloy and the cast iron block. I would also seek to repair the orig mounting tabs. Just me though.

Pics of the bad/damaged, motor mount pads might help with opinions on how to fix it.

Biggest concern would be that the blocks are designed with the original mounts in those locations. Added addition stress to other areas not designed for it (due to vibrations and weight of the block on the mounts) I would advise not to do this. If this were some super cheap rat rod that you were throwing together as a cheap toy that isn't expected to last long I would think it would be ok. Also the stresses of heating the cast iron block and then welding too it would cause more problems and I can see maybe if it were a fully filled block with no coolant passages you may be ok.Fixing/reusing stock mounting locations is really only correct and safe way to do it.

People with higher HP engines have stated that mounts on the side of the block can distort the cylinder bore under load.

Whether this is true or not, I have no idea.

^ this

Actually I am thinking that if you do this to a "valuable" block then you will no longer have a "valuable" block.

I'd go with tried and true and would either repair the existing mounts, or would use a motor plate.

Yep, done to death, super boring, and not thinking out of the box.

Not to say the proposed solution wouldn't be functional, but Sometimes over-utilization of creativity and imagination can bite you later on, like if you ever need to sell any of it....

Getting away from the stock mounts and welding a plate on the side of the block sounds like a recipe for disaster.

The OE blocks are not thick. Dissimilar metals. Cracks. Failure of the block is how I see this ending up.

OK thanks gents, good points.

In this case I'm not referring to any specific block, just a general case, so no pics.

I will add this, to the point of changing the mount location on the block adding stress,
that is exactly what is happening when using a front motor plate.

As far as welding a steel plate to cast iron, I thought you could safely do that, maybe not.

Personally speaking, the resale aspect doesn't concern me, but that is a good point.

What if you wanted to put a Hemi in an old truck, would you use stock Hemi mounts in the stock location ?

****

I think the outside wall of pretty much any block is not attached internally to anything, just top & bottom, front & back.

"What if you wanted to put a Hemi in an old truck, would you use stock Hemi mounts in the stock location ?"





use the stock engine mounts, and fabricate what is needed to the chassis of choice. not a particularly hard task.
cardboard, chip board, etc. is your friend here.
position the engine in the desired position, then cut out the cardboard to the desired pattern for the mounts, transfer the pattern to steel. weld away, done.
as to welding a plate to the engine block, no...........

Changing mounting location with front motorplate is different because you have solid surfaces you are mounting to (ie water pump mounts) that are designed to hold weight vs if you weld to side of a block you could be going to coolant passages where section are weaker. If anything you could machine off the mounting locations and then weld to the stock locations as they were designed for the weight and stresses.

You can weld to cast iron its just you are heat treating the block and the areas you are welding to are not designed for certain forces/loads.

For an old truck you would make plates to adapt to the stock mounting locations on the block or you would modify the truck side of things to mount to. Just like any brackets like schumacher or the new holley brackets for gen 3 hemi are just adapted to fit the block locations and then connect to stock engine mounting locations on the older cars.

Like said previously it could be done but how long will it last and what will break first who knows? If you had a repaired block with missing mounts and had a beater to build then yeah could be worth trying.

Cast iron and steel are two different metals, they don't weld very well. Second anytime you weld cast iron you have to pre heat and cool down slow in an oven or it imparts stress, and it will crack guaranteed. I have lost count of how many engine blocks that have been welded on causing more grief. Friendly advice never weld cast iron unless you have an expert with an oven big enough to hold a block.

Id use an engine place and a midplate. I've been doing that way for years and NEVER an issues with an stress or wear from the plate. I have done this from 800hp to 1200 and change with Mopar stuff and not an issue

First thing I thought of when I seen this question. Total shade tree, but you have to admire what they are capable of doing with what they have access to.

https://youtu.be/mi_NSFq0r8I

Well I have always heard welding cast iron is tricky.
Let me add this, many moons ago I had a welded stroker crank, crank was a cast Buick 455,
made a 535 inch street motor with the T/A Stage 2 heads. Horsepower level, who knows, 650 ??

I still think it would be OK to relocate the mount positions on the side of a Mopar block, from a stress standpoint,
but perhaps not from a welding standpoint.

There are many things that -can- be done.

Would be amazed if relocating mounts and welding 4x4 plates onto the side of a block resulted in any better result than fixing the original mount locations at less than 10 times the time/effort.

A thermal mass analogy:

Compare this to welding a gum wrapper to the Titanic hull.
How to get (and keep) them at the same temperature? How to pre-heat a block?

Don't do it.

OK talked out of it.