Here is my DIY procedure for changing the G35/350z engine mounts. There are other DIY procedures but they all involve using expensive tools or modifying a wrench using a welder to get at the driver side mount top nut. I used a Snap-On torque adapter and Harbor Freight everything else.

With the correct tools and following this procedure, the hardest part of this job is getting into the passenger side engine mount bracket rear nuts because of the lack of access. Make sure you can get a wrench on these bolts before you start.

Tools needed for this job:
- Metric sockets and ratchet, breaker bar, and torque wrench
- 14mm torque adapter (Snap-on 3/8 drive 14mm torque adapter can be purchased online for $30)
- 3/8 extensions and universal joint
- 14mm Ratcheting flex head wrench
- Optional but recommended (I did without but if you have large hands you need this): Long 14mm wrench for reaching and breaking passenger side rear engine bracket bolts. Ratcheting would be a plus as then you wouldn't have to stick your hand too deep in to get it off the rest of the way.

Procedure:
1) Drain oil, remove filter, disconnect battery (you'll be working very close to the starter, I almost got zapped)
2) Remove driver side engine mount bottom nut.
3) Jack up driver side of engine (distributing force on the oil pan with wood block) enough to get access to the driver side top nut. Use the torque adapter universal joint, extensions, and a breaker bar (see below pic) to break torque, and the 14mm flex wrench to get it the rest of the way. DON'T STRIP THIS NUT!!! Put the engine back down on the old mount with all the nuts removed.

Breaking torque on driver side top nut

4) Support engine with mechanical jack for safety, using a hydraulic jack to do the actual lifting. I had both jacks sitting on the same wood block under the oil pan.
5) Use the long 14mm wrench and/or swivel wrench to remove the 4 bolts holding in the passenger side engine mount bracket. Attack the rear bolts from directly behind, as you can't get a wrench straight up to them. This is the most tedious part of the whole deal. Additionally, if you back the top rear bolt out all the way out with a ratcheting wrench you won't be able to get the wrench off the head because of the tight clearances, so either leave that one until last or finish the bolt off by hand or with a regular open wrench.

This is a regular length wrench attached to the top rear passenger side bracket bolt. Good luck.

6) Remove passenger bottom engine mount bolt
7) Jack up engine as far as it'll go, make sure you don't break anything though.
8) If your engine mounts are broken (or almost broken) you should be able to pull/twist them apart as shown below and get them out with clearance to spare. If you can't, you might need to lower your K-member for more clearance, which I didn't need to do.

Pulling broken driver side mount out with top nut loosely attached. You could cut it out as well if you didn't want to drop the K member.

9) On my 14 year old 130k mile Maine winter driven car, both sides had cracks in the K member where the engine mount was supposed to bolt up, and I was able to hammer out pieces which would have broken eventually if I had ignored the cracks. I removed the rust, repainted, JB welded the broken piece back into place, and fabricated steel washers to distribute the load away from the broken area. A couple pictures of my repair follow. I recommend adding washers even if your car doesn't have cracks to prevent them from developing in the future.


My K member after hammering out the broken piece.


JB weld and rust converter FTW. Don't worry I'm not leaving it like that!


Dimension of fabricated washers to distribute stress. Got the steel from Home Depot, used a sawzall, angle grinder, and drill to fabricate. Installed pictures come later.

9) Put new mount on passenger side bracket outside the car, pay attention to torque values (read the instructions) and use loctite. You don't want these to back out, but over-tightening will stress the aluminum bracket and cause cracking.
10) Reinstall passenger side mount and bracket, using loctite on the bracket bolts. Reinstall driver side mount to engine by tightening the top nut with the 14mm flex head, but don't torque it yet.
11) Lower engine, making sure the engine mount studs line up with the holes. Tighten the passenger side bottom nut (Again, torque matters here). In my case, I put my fabricated washer on before tightening the nut as shown below:

Bottom nut installed with washer to distribute load on the K member. Should be stronger than stock.

12) Jack up the driver side of the engine for more clearance if needed and torque the top nut using the extensions and 14mm torque adapter. Don't strip the nut (or if you do, make sure it's tight....)
13) Lower engine, and torque the last bottom nut. Reinstall oil filter, and add oil! You're done, now go do some WOT redline shifts and notice the difference! The mounts get (slightly) smoother at idle after 500 miles or so.


Sweet sweet success... and don't forget the oil and filter like I almost did!


Impressions on the Z1 mounts: My shifter barely moves now (only because of rubber trans mount), and throttle response is greatly improved over the broken old mounts. I know my mounts are virtually indestructible now so I feel less guilt beating on my car every day. It seems easier to break the rear wheels loose on the track as well since torque delivery is so instant. Shifting is much more precise especially at redline since the transmission moves less, and there's less of a tendency to grind going into 5th and 6th with my 130k mile CD00NOT9. When pushing the car hard, I love them.

There isn't much additional NVH while driving although I can definitely feel more vibrations in the wheel, seat bottom, and pedals. I also get some mirror-rattling vibrations around 2500 RPM, especially when engine braking, which passengers certainly notice. This could be the new mounts exposing a problem my car has, or it could be that the VQ just does that. The whole effect is that the car has much more of a "race car feel".

At idle, there's much more vibration in the seats, and at particularly lower RPMs something in the roof buzzes like crazy which is definitely annoying. I'm going to do an idle air relearn and clean my throttle body to hopefully stabilize my idle to a RPM which doesn't cause this, as it's VERY annoying unless the stereo is really bumping. If your car has a sketchy idle, be prepared to constantly worry if you install these mounts as you'll both feel and hear your engine's RPM change even if you have a stock exhaust.

If I were to do this again on a car I planned to have passengers in, I'd install some OE mounts or VibraTechnics combined with a torque damper as the buzzing and vibrations particularly at idle give the impression the car's broken, forcing me to explain it's because of the "racing" mounts.

 

Lol I literally just installed them yesterday as well as the transmission mount when I put in a new transmission because mine was starting to wear the synchros. My motor mounts LOOKED fine but after installing these Z1 mounts I can tell they were definitely worn, I honestly don't think there is hardly any noticeable difference in NVH but it does hold my shifter a lot more steady when smashing the throttle on/off quickly. With the old mounts I used to get quite a bit of play in the shifter, about 3/16" or so.

I'm with you about not doing them with the engine in the vehicle, it was a pain in the butt. I hacked up a gearwrench and welded the handle on at a different angle which helped a ton.

 

I managed to get the tough bolts broken with a swivel head ratchet wrench and another wrench for leverage. Only thing was there wasn't enough room to get the second wrench hooked into the first wrench right so I had to duct tape one in position just so I could get the ratchet onto the head.


Now that that's done and the car's sitting I'll order the Z1 mounts as I just don't trust a $40 pair of engine mounts to last... Although they would probably be fine.with a typical driver.


My shiftier jumps on/off power in any gear, even in 6th, I can see my RPMs bounce a little bit, and I can see a tear in the passenger side mount when I jack up the engine a bit. I repaired my car's torque damper which helped a LOT but it turns out the hole in the block was about to strip and the damper worked its way out again so I'll have to find a bigger bolt and re thread the hole. Back to school now so won't be touching the car for a few weeks.

 

I spoke too soon, although i can get a swivel head ratcheting wrench on the driver side top mount bolt there's no room to turn the thing without having it come off the head, and no leverage anyways...
There is is all the way at the bottom! Note the terribly designed wings on the motor bracket preventing access from any direction but directly facing the frame... Doh.
This is as far as I've gotten but because of that angle and an inability to get leverage the tool always slips off.
Took off bottom mount nut and jacked up engine trying to get more room, this is what the better of the two mounts looks like...
I also tried using a crowsfoot wrench which would have done the job but because of those wings on the mount didn't let the wrench engage far enough with the nut to turn it.

I'm at a loss... anybody have ideas? I don't have a welder so making frankenwrenches isn't an option.

 

Updated this thread with a tools summary and DIY at the first post. I ended up buying a "snap-on 3/8 drive 14mm torque adapter" for $30, which allowed me to do this:



With this tool, breaking the nut as well as re-torquing it was a relative breeze although you still need to be careful not to strip the nut, which would be nothing short of an engine-out disaster.

 

Great idea using the torque adapter, I wish I'd have thought of it instead of butchering an old ratcheting wrench and welding it back together in frankenstein fashion.

I had to go through my entire cabin with gorilla duct tape, dynamat, and a LOT of that 3/4" round foam and fix a lot of rattles and stuff after I was done but the interior is completely silent now. Most of the stuff in the door panels I just gorilla taped flat against the mating surface, I stuff the foam into a few pieces around the dash that were rattling, around the coupe rear passenger windows as well, I used a plastic spoon to really stuff that foam in nice and tight so you don't even see it anymore. The only part that was a pita was some wiring for the sunroof because I had to drop the headliner. Definitely worth the couple hours it took me to get rid of the rattles, downside is anything you put into the door pockets will rattle, I folded up a couple microfiber towels and leave them in the door pockets now to keep my little bottle of hand sanitizer and coffee cup from driving me insane.

 

I've already gone thru and de-rattled my car right after I bought it, and the only thing left is dropping the headliner which there's no way I'm going to do until my sunroof or something else up there breaks. It's good to know that my only buzzing sound is fixable though so thanks!

Also, are you able to move this to the DIY section? This is the best step-by-step procedure on the internet for these and the only one that doesn't involve welding wrenches or using tools you can only get in a $400 set.

 

Probably gonna have Blue do that, I'm still figuring out what all these buttons do lol.

EDIT: You should edit the first post so the DIY is at the top of the thread so folks don't have to dig to post 5 to find it.

 

I just went and compiled everything relevant into the first post.

 

Fellas I don't know if this is really DIY section material..........





















































But I'll move it over there anyway. Fantastic write up csw, thanks for putting this together.