Aluminum motor mounts

[Nthe11s]

need some info. i am building a set of solid motor mounts and would like to use Aluminum. what grade would be suitable? as there are quit a few to pick from. i was thinking 6061-t4 (3/16 or 1/4). here is what i was thinking.

or


also what filler and would i need to re-harden the aluminum after welding

i am using a Syncrowave 200 non-water cooled

any idea would help....
Thanks Rich

[Paul Seaman]

The engines size and power will weigh into this equation. I would warn away from thin 1/4" mounts on a big block for instance. A high torque small block would be over the top for 1/4" as well. WE need more Information. All the little things matter in these decisions. Also what is the design purpose of this vehicle also. If your doing an off road truck this is a terrible idea as well.

[Nthe11s]

engine is a 4.6l 281 Crown Vic with around 550 flywheel hp. Car will be used for Street/Strap.

here is a pic of factory mount

[ridesideways]

if you make all those welds pictured in your little diagram, your 6061 will probably lose all it's temper from the heat and will end up with no more strenth than non-heat-treated aluminum. if you're dead set on aluminum, the i would machine the motor mounts from a block of 7075.

[Sberry]

I kind of agree about not being so dead set on alum unless I copied a proven design, they are small and weight would be rather insignificant to some extent, I would be tempted to use steel unless I had to use alum.

[Paul Seaman]

If aluminum is the requirement, then I would step to atleast 1/2" material. I also agree that a machined block of material would have a better chance. Also if 1/" is used I would relief cut the surface to slightly recess the bolt head and thus move the strain into the block as opposed to being carried pirmarily along the surfaces.

This I believe to be a true call for steel, but as usual its my opinion.

[trstek]

If you make them out of aluminum, put some safety chains or cables on to limit travel.

First few runs keep a camera on it.

We like pictures.

[Fishy Jim]

BMW motor mounts on their 400+hp v8's are all just vulcanized rubber with a couple studs going off either side. NO mechanical connection within the mount aside from the rubber bond. They have steel cups that interlock in the event of a failure (which does happen, and has happened to me on a raced e30), but there's nothing holding the engine down.

1/4 or 3/8" 6061 would probably work without any issues, depending on design.

Now about the design; it's flawed. You have openings on either end that don't need to be there (they create a cantilevered stress zone across your joints). Intend on turning your bolt from below and make the ends boxed, then you'd be good to go.

What you created is a bracket that holds a rotational load against the weakest dimensional axis of the part. This is aluminum too - it has a significantly smaller stress life than steel. Eliminate the flexing at the welds and you'd be home free.

[Nthe11s]

hey guys thanks for all the info. i am not dead set. just an idea the drawings are kind of what i was thinking of for designs. i draw up another drawing that boxed the mounts in. i will build a set and test them out on the car hopefully it works.

also i was reading that after welding 6061-t6 you can re-heat to 900* to get the strenght back.... is this right?

[trstek]

bmw also has very little body flex. They tend to be designed very rigid.

The ford's I own, they flex a bit more than the bmw's and other german designs. The germans like to alloy, what kind of aluminum do they use?

4.6 v8 is very smooth in the delivery of power, at least mine is in my svt. course, I can get the body to flex, launch or twisties...

Strip launch's will put instant stress and twist in a body in ways a road car will never see unless it's bouncing off a wall.

Not good, not bad, just a bit different...

If it is not a proven design , I'd put a safety chain/strap on it to keep it from eating other parts up if it decides to let loose.

Just my opinion.

[Nthe11s]

bmw also has very little body flex. They tend to be designed very rigid.

The ford's I own, they flex a bit more than the bmw's and other german designs. The germans like to alloy, what kind of aluminum do they use?

4.6 v8 is very smooth in the delivery of power, at least mine is in my svt. course, I can get the body to flex, launch or twisties...

Strip launch's will put instant stress and twist in a body in ways a road car will never see unless it's bouncing off a wall.

Not good, not bad, just a bit different...

If it is not a proven design , I'd put a safety chain/strap on it to keep it from eating other parts up if it decides to let loose.

Just my opinion.

yes, for the test i will have it chained or straped. i will update with pic and results soon.
Thanks Rich

[Fishy Jim]

Trstek, I'm not sure what alloy they use, but you're right - the whole rear suspension and sub frame on my e39 is aluminum, as are the front suspension arms.

What I was getting at in the other post was that the thickness of the plate was getting excessive and that it still didn't provide the rigidity to counter the flexes the engine will induce on it. Boxing the section would eliminate the issue.

[Flyingpig]

First Ill say Im not familiar with the 4.6 or the body youre using.

If youre going to use solid mounts forget making your own like that and use motor plates. These are simply flat plates bolted to the front of the block and bell housing. They are ultra simple and you can usually get a universal design which you can trim for your specific application. You will have to add shim material between the flywheel and converter to insure proper engagment to the pump.

Should you doubt the integrity of the simple design keep in mind that is what is used on those 6000 horsepower fire breathing nitro cars. My digger uses the same thing even tho its only an 8 second car. Working on the car is faster as the engine can stay put as you pull the trans and vice versa. Having the mounts in the middle of the block will require supporting one end of the parts that stay in the car. Installation and removal will go much smoother as you wont be reaching into a dark hole trying to get a bolt started.

[pro70z28]

I agree with the motor plate/mid plate idea.

IMHO I wouldn't use shims on the converter though. I'd have the correct extended mounting pads welded on the converter by the manufacturer.

[H80N]

slightly off topic ... V8 E30??

Fishy Jim
had you done a (bmw) v8 conversion in your e30?
thanks
Heiti