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casting my own engine/trans/diff mounts

Old Jul 4, 2010 | 01:02 AM
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casting my own engine/trans/diff mounts

i know this is pretty ghetto. but i think it could be a cool project to see if it would work, and im just not willing to pay upwards of 60 bucks a pop for a chunk of rubber when i could probably just buy a big tube of it and make all 6 of these things myself. not like they are ever seen at all, so i dont care how ugly they are lol

these parts are not very intricate at all and would be pretty easy to make a 2-piece silicone mold out of....but im wondering, if i cast these out of polyurethane, how hard is it going to be to release that from the silicone?
will it bind to the silicone or just peel off without destroying the actual mold itself?
what kind of silicone should i make the mold out of (if it even matters)?

im probably going to go with the same stuff reccomended in some writeups for fixing worn mounts, which is 3m window weld. only thing is, my mounts arent repairable, they are solid chunks and as such i need to make the entire piece from scratch.

if anyone can reccomend any other materials to cast them out of be my guest. i dont want it to be solid as a rock but i dont want it to be really soft either.


also how about drilling the mounting holes in it? should just be able to drill it out with a twist bit without any problems right?
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Old Jul 4, 2010 | 10:35 AM
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If you are going to take that approach, just cut some aluminium pucks and drill a hole through them.

Technically, this is the improper way to make engine mounts regardless of material, but in practice it seems to work fine most of the time.
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Old Jul 4, 2010 | 10:38 AM
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that would be far too harsh for what im looking for. i want some sort of rubber thats not going to transmit every single vibration to the chassis
i want something similar in hardness to the urethane mounts you can buy, without paying 60 bucks a piece :P

and yeah i realize this isnt really "proper" but it should work if made from a decent material, and i'm up for the challenge and possible screwups :P
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Old Jul 4, 2010 | 01:15 PM
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Is this going into a street car? The Mazda competition mounts are plenty stiff and are only $41 each: http://www.mazdatrix.com/getprice.as...m=39-0400-FBY1. I'm using a pair now, and I couldn't see myself wanting anything stiffer. Engine vibration is increased some, but not to the point that it is irritating. And when revving the engine barely moves. This probably isn't the answer you're looking for, but they'll be a lot better quality than home-made mounts.
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Old Jul 4, 2010 | 01:27 PM
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home made doesnt have to be ghetto....just requires the correct tools. give it a shot, what do you have to lose?


i make them out of 3 pieces...delrin/aluminum/delrin and they are very stiff but not quite as stiff as solid aluminum...lots of people like them and i will run them in my car
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Old Jul 4, 2010 | 02:46 PM
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Gurew what exactly do you do to make them? i was thinking of just filling a box with the OEM part inside it with silicone, cutting that in half to form a mould out of it, and pouring the 3M window-weld into that mould to make a stiffer copy of the original

im not too worried about the diff mounts because theyre in pretty good condition but the engine/trans mounts are pretty worn as there is a good bit of movement in the drivetrain
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