Ok captain physics, here we go.
Most/all motor mounts have a fastener mounting plate to plate with some kind of cushion in between (or just a block of aluminum for a solid mount) another plate:
(sorry randy for stealin' ur photo)
Sort of like a plate sandwich with a rubber or rubber/oil filling, sometimes aluminum. Like a manwich.
Anyway, a bolt does not function in shear or bending, it's only intended to work in tension. A fastener's torque is calculated based on the area of the mounting faces and their coeffiecient of friction. The point is that the faces of the metal plates are under enough pressure from the bolt that they cannot move in any direction... this leaves the bolt under permenent tension, NOT shear. If the bolt were to come loose, the faces of the mounted plates would no longer 'grip' each other, and would thus bend (or shear off) the bolt when the loading capabilites of the bolt were exceeded. Which, isn't hard when you're leveraging a 700lb motor.
Now, the point of all this is that a hockey puck motor mount is essentially a long bolt with a few pucks as spacers. And then you tighten all that down, squishing the pucks together. Now you vibrate the shit out of them, heat them, get oil on them, cool them, heat them again, and torque the crap out of them launching the car, ect... Now the pucks have squished some and there's going to be a smidge of play left over as a result of the rubber compressing... so the bolt is now holding the engine steady instead of the mounts.
Think of it like this: put a 1/4" bolt in a vice and have 3" of it poking out, tighten that vice down good. Now grab a hammer and give a good wack. It probably bent. Now, take another 1/4" bolt, drill two holes in some angle iron and bolt the flanges together, stick the flange of one of them into the vice and give the flange of the other a good wack, it won't be nearly as easy to bend... because the bolt is in tension holding the flanges together (if you tightened the bolt just enough).
This is what a hockey puck mount will get you:
http://www.m3forum.net/m3forum/showthread.php?t=172089
The purpose of a fastener is to hold structural members together, not BE a structural member. If you will, a standard motor mount as shown above from BIC, imagine how that moves under load. The bolts do not take any fluctuating load at all, no matter what the engine is doing: it is
only preloaded by the torque from the nut. What actually holds the engine in place is the sandwich filling, the rubber in between... the bolts simply hold the rubber's mounting plates onto the chassis and motor.
If that explaination isn't simple enough to understand, strap in those hockey puck mounts and go drive into a wall at 50MPH, let me know if the engine stays put. If it does, I'll not only believe you, but I'll apologize, and I'll even buy you a beer. Now you just can't get more reasonable than that, can you?
I really don't think $15 is enough to spend to hold 700lbs of engine in place. I think there should be a bit more engineering there, but that's just one guy's opinion. There's really no way to turn a hockey puck into a bracket without some serious thought and design, otherwise it's simply a cushion. And since it's cushioning a bolt, which is holding in an engine, the bolt is really holding in the engine, not a bracket. Do you really think this is wise? Itty bitty little bolt, bigass engine? What do you think will happen to those two bolts when that engine tries to decelerate under crash conditions? It's going to shear off. And where do things go when they break off of something that was moving, captian physics? Newton's first law, in the direction it was originally going... which, in most cases, will be straight ahead.
You're really not looking at this problem three dimensionally; a bolt is not intended for that purpose, that's why GTI kid's bolt looks like the start of a pretzel baking project.
I know a guy who ran hockey puck body lifts on his truck, until he was in a T-bone accident and his cab was thrown 25ft from the rest of the truck. Amazingly, he didn't break too many things, but he was ok. Why did the cab become disconnected? Some idiot replaced the body
MOUNTS with cushions and the bolts sheared off.
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