Opinions on Engine mount filler material

OK, so the decision has almost been made for next year's auto-x season. The decision to go full tilt STF build for the SeX is on. Whiteline has the control arm bushings covered, header/cat/tune are decided. All that is left is engine/suspension mounts that are 2/3 shot with all the hard launches this car has seen in 3 years of auto-x and drag starts.

Since NO ONE makes engine mounts for hte big block Forte, my only real option is to snag a spare set of mounts and fill them with a hard epoxy. Looks like the common theme has been the 3M 08609 Window Weld. But is there a better option? Do you cut out the stock rubber and fill them completely?

New for this so help a brother out!

seth at the challenge did this for his maxima using 80 durometer utherene. he said it was from an internet kit and was easy to do.

I'll look for his build thread. Edit: https://grassrootsmotorsports.com/forum/build-projects-and-project-cars/grm-2015-build-i-bought-back-my-old-maxima/97332/page3/

I've done the 3M urethane trick a couple times- fixed wheel hop on my turbo'd Swift GT without increasing the NVH much at all. Note this was just sandblasting the existing rubber, and filling the stock voids. Never tried a complete gut and replace but that would be much stiffer than keeping some of the OEM rubber in place.

airwerks wrote: I've done the 3M urethane trick a couple times- fixed wheel hop on my turbo'd Swift GT without increasing the NVH much at all. Note this was just sandblasting the existing rubber, and filling the stock voids. Never tried a complete gut and replace but that would be much stiffer than keeping some of the OEM rubber in place.

the stockers are just about completely ripped, so as one could imagine the wheel hop is tremendous with 170ft/lbs (before tune) trying to shove the front wheel into the door jams. I may try filling new mounts first and keep the old ones. If it's enough, good. If not I can gut the old ones and completely fill them for more stiffness.

On my old 2nd gen Neon I used JB Weld in the motor mounts. After I filled them I baked them at 200 for about an hour. After a couple months I did see cracks in them but they were still solid.

whatever you do do not remove the old OEM rubber from the mounts just fill the voids. I did that to a junkyard set I had and used the same 80 durometer polyurethane as seth in his maxima. the mounts where garbage after a week. I ended up filling the stock ones with some extra polyurethane I had and it worked great.

Or I could have some aluminum ones made! I bet those won't transmit any vibration at all!

This is what I used on the transaxle mount for my 951s:

http://www.mcmaster.com/#8644k11/=zjz8ev

Worked great and the added vibration was pretty minimal while the ability to put the power down increased nicely.

Bobzilla wrote: Or I could have some aluminum ones made! I bet those won't transmit any vibration at all!

Not legal to STF

I used 3M window-weld on a Mazda3 mount years ago. Worked pretty well but it takes a LONG time to fully cure. It was hard after 4 days, and when driven on it a tiny bit spurted out that wasn't fully cured in the middle.

http://www.mazda3forums.com/8716809-post16.html

It worked really well and was a good budget solution. Go buy a new mount and fill it and let sit for like 7 days is the right way to do it IMO.

For my Mazda2 I made my own with some $20 energy suspension bushings:

That is likely your best bet if you can weld. And if you can't, its a good excuse to learn but then you end up making stuff like homemade struts and stuff

I used the McMaster stuff above several times.

IMO, dropping to the 60 durometer still had 99% of the benefits, but was about 50% easier to deal with from a vibration standpoint. Its not like it needs to be completely rock solid... most of the increased stiffness is coming from A) having something not broken and B) filling huge void areas.

I use the McMaster stuff. After a thousand miles or so, it mellows out to not too bad from a vibration standpoint.

I've heard for years that kids use "Shoe Goo."

Yup, I highly recommend the stuff I used for my Maxima mounts.

www.energysuspensionparts.com/diymmi

They were easy to do, that kit had enough for all 4 of my mounts plus a little left over. They look pretty cool too, at least one side does. There are some pics in my build thread of the end result. Hard to beat for $35 shipped.

There's a good writeup on the RX8club site about filling fluid filled mounts with that McMaster urethane.

Link one

Link two

I've filled stock mounts with 3M Windo-weld, it's worked well, it made the mounts a lot stiffer with little increase in vibration. You just have to do good surface prep on the originals or you'll have two perfect moulds pop out the sides when you start the engine.

kb58 wrote: I've heard for years that kids use "Shoe Goo."

The kids are wrong. This happened after a couple of months when I listened to them. Bad call.

Yeah Shoe Goo is very soft and gooey. I would definitely recommend against using that.

It's got a rather low melting point, too.

ProDarwin wrote: I used the McMaster stuff above several times. IMO, dropping to the 60 durometer still had 99% of the benefits, but was about 50% easier to deal with from a vibration standpoint. Its not like it needs to be completely rock solid... most of the increased stiffness is coming from A) having something not broken and B) filling huge void areas.

I have to agree with this statement. I have done the same thing with similar results. When you see a failure of the urethane like posted earlier it's usually due to a bad mix, not enough cure time, or old product. A bad mix or improper ratios has always been the reason for any failures I've had.

The two best options is to find a urethane that is a 1:1 mix or use a scale when mixing if the ratios are different.

What you guys need is Smooth Cast from a company called Smooth-On. It's 1:1, cures in less than an hour, and is fairly cheap. Ive used several of their silicon and urethane products to mold and cast Porsche 908 parts. Very good results.