I'd been meaning to post this on here since December, but I knew how much time documenting it correctly would take, and life kept getting in the way. And, as long-winded as I know I normally am with this stuff, I’ve already omitted a bunch of semi-superfluous details, but it’s is going to be unavoidably long anyway because of all of the variables and combinations of materials, etc. Anyway, sorry for the delay, but here's what I did...

After thinking about how ridiculous it was that my factory engine mounts went out at ~50K miles (one of them was completely torn in half), I decided to try to find a "better" alternative. And, since I’ll keep my XFR as a toy for as long as I can and it’s doubtful it’ll ever see daily driving duty again, I decided to bypass the OEM liquid-filled mounts to look for something a little more visceral and fun (less squishy). Plus, my local dealer wanted $350 per OEM mount, which was just really annoying on general principal, as I know I could’ve gotten the OEM mounts online for under $200 each (and well-made custom engine mounts for ~ $250+ total for both).

Since there really aren’t too many Jaguar-specific options available (are there any at all?), I started looking at OEM and aftermarket mounts for GT500s, CTS-Vs, Corvettes, etc. I then stumbled across a Jag thread on here from two plus years ago whereby @Buickcadillacman had strapped some Hinson urethane mounts meant for GM applications onto his S-Type R. They were shorter than the Jag OEM mounts, and they used M12 bolts instead of the Jag OEM M10 bolts, but he just added spacers and drilled out the engine mount brackets to accommodate the larger bolts. Unfortunately, Buickcadillacman hasn’t posted anything in over a year, so doesn’t appear to still be active, and I couldn’t get any feedback from him about how they worked out.

But it did get my tiny brain turning. As another expensive hobby, I build a lot of custom speaker & subwoofer enclosures, some of which have been 500+ lbs. each to accommodate the ported volume requirements for huge drivers, some of them are 300+ lbs. and “floating” on custom plinths, and some have been designed and integrated into furniture, interior walls, etc. All of that is to say that I’ve done a lot of work on decoupling and isolation for Home AV (as well as a lot of car stereos, years ago), and I started thinking through custom engine mount options. It led me to more fully appreciate the complexity of engine mounts; not only do they need to provide stability by supporting the weight of huge engines while under load at varying directional G-forces, but they also need to make sure the bolts don’t shear, rust, interact with other metals, etc. All while still incorporating the “preferred” NVH characteristics of engine mounts, which is extremely subjective, and they also need to be resistant to all of the additional stresses of an (supercharged) engine bay (heat, chemicals, etc.).

As I quickly realized that I had no plausible ways to thoroughly test any of the variables on my own ground-up engine mount designs without spending years continually installing, removing, and tweaking them, I started to look at existing aftermarket mounts which had what I thought was a great initial design, and could also be easily modified to fit my application, with the added benefit of being able to do some fairly quick minor tweaking, as needed.

In case anyone is interested, I’ll document the measurements of my OEM mount (C2D2745) which didn’t shear in half (I have pictures of these and additional measurements, upon request):

Jag OEM Mount (C2D2745):

• Total Bolt Tip to Bolt Tip Height of Mount: ~152mm
• Body Height: ~91.25mm (removed from car, but probably compressed a few mm after years of use)
• Top Bolt Length: ~25
• Bottom Bolt Length: ~33mm

I eventually came across some really beautiful mounts which looked incredibly well-made and were designed for C5/C6 Corvettes: AMT Motorsport Vulcan Motor Mounts. Like the Hinson mounts that Buickcadillacman used, they’re shorter than our OEM mounts by about 18mm, but that seemed like an easy hurdle to overcome. Additionally, Mark Petronis, the owner of AMT, actually races Corvettes and AMT Motorsport is, first and foremost, an automotive machine shop, with Mark designing the mounts, etc.



For his mounts, rather than using urethane, Mark designed two maroon aluminum cups which encapsulate two pieces of vulcanized rubber at either end, which then sandwich a gray Delrin disc in the middle. I won’t go into all of the technical merits about why it seemed like a good idea after reading about ten-hours’ worth of info on polyurethane engine mounts, but a few of the things that I really liked about them is that, in addition to the encapsulated rubber comprising the majority of the cushioning, Mark uses a single bolt in his design, which makes the mounts a LOT easier to get in and out (bolt goes from bottom to top), and it also prevents the mounts from shearing in half, thereby preventing the engine from jumping around like a House of Pain video, the way it does when the OEM mounts tear in half. Additionally, the 18mm shorter stature than our OEM Jag mounts gave me some options to tune the mounts with different materials to achieve the desired NVH, etc.

Anyway, after sharing my dimensions with Mark and a brief conversation, he said that he was going to try to modify them for use on my car. That included using longer M10 bolts, rather than the shorter M12 bolts it usually comes with, as I didn’t want to drill out the Jag brackets (which the mounts sit between) to accommodate M12 bolts (I checked and M12 wouldn’t go through the brackets), in case I decided to go back to OEM at some point (it'll never happen, now, though). To compensate for the skinnier M10 bolts inside of the mount holes meant for M12 bolts, he said that he was going to put a sleeve around the bolt. He’s also said he would fabricate some aluminum spacers with the correct ID for the M10 bolts as a starting point to achieve the desired height, NVH, etc. I mentioned potentially using some polyurethane spacers to add some of the cushion back from using the solid shell, but he thought that I should let the vulcanized rubber do as much of the isolation as possible.

Ultimately, Mark kind of forgot about customizing the mounts for me for a while, and I started getting kind of impatient, so he eventually sent the mounts with the aluminum spacers, but without adding a sleeve for the M10 bolt to go through. He had a LOT going on, though, as he’d recently been in an absolutely horrific accident at New Jersey Motorsports Park in his Corvette, and he was extremely lucky to still be alive (seriously), so consequently he was going through extremely painful rehab for multiple hours over most days of the week. So, I definitely cut him some serious slack. I should also mention that he very politely said that he wasn’t interested in further customizing his mounts for various applications, which I completely understand. But what I ended up with was really just his unaltered mounts, which I then took upon myself to customize. So, if anyone else is interested, just buy the regular ones from him and get to work. I'll explain...

For multiple reasons, I didn’t really like the thick aluminum spacers which were meant to be mounted on the bottom of the dual maroon aluminum cup enclosures, including that they made the total mount height about 4 - 5mm (~1/4”) too tall, so I decided to ditch them right out of the gate. Instead, I focused on what else I could sandwich inside of the dual maroon aluminum cups to achieve the desired support, height, NVH, etc., so I started experimenting with a lot of options, including the following:

• Various durometers, thicknesses, and diameters of polyurethane pads from Energy Suspension with I.D.'s to accommodate M10 bolts (to go inside of the maroon aluminum cups - including some square pads which I had to drill out with a hole saw to the correct sizes, then sand the edges smooth, etc.)
• Smooth-Bore Seamless 304 Stainless Steel Tubing (1/2" O.D. and 0.049" Wall Thickness) which I cut to various lengths
• Various lengths of M10 x 1.5mm thread high-strength zinc yellow-chromate plated steel hex head bolts
• Various thicknesses and diameters of high-strength stainless steel washers with I.D.’s to accommodate M10 bolts (to go inside of the maroon aluminum cups)
• Various thicknesses and diameters of high-strength zinc yellow-chromate washers (and nuts) with I.D.’s to accommodate M10 bolts (to go outside of the mount brackets)
• Silicone brake caliper grease (between the discs and pads, on the bolt shafts, etc.)
• Loctite PL Roof and Flashing Polyurethane Sealant and FlexSeal liquid (to help fill the gaps between the M10 bolt and the M12 holes)
• Reflective wrap and ties, etc.

I tried a lot of options, including installing, removing, and tweaking the mounts continually comprised of various combinations of materials. I initially used some of the metal tube to slide between the pads, so the bolts could slide inside of them with no gaps, but I was afraid that if the tube was cut long enough to go completely through all of the pads, the tube would bottom out against the insides of the maroon aluminum cups (or the steel washers between the pads) upon compression, and if the tube was cut short enough to prevent bottoming out, the poly pads might “slide off of the tube tracks” inside of the aluminum cups, etc. I also tried mounting Energy Suspension body spacer pads under the bottom mount brackets for additional cushioning, but they were too soft and compressed like thick jelly when tightened up. It was really hard to tell what was going to work well under the combinations of compression of the tightened bolts, variable twisting torque of the engine, etc. I won’t bore you with all of the combos which I didn’t think worked well for various reasons, but there were a bunch, including not only the materials, but also the placement of the materials inside and outside of the maroon aluminum cups, etc.

I documented the great majority of my failures, but when I finally found the right combo, I was so sick of dealing with it all that I wasn’t as diligent as I should’ve been in documenting the exact final working combo measurements, but here’s what ultimately worked for me (and worked very well) to the best I can recall (in order of my mount sammich):

• AMT-provided Maroon Aluminum Cup
• AMT-provided Vulcanized Rubber Disc (~1/2” Thick) sits completely inside aluminum cup
• FlexSeal (thin layer for washer to sit in) sits completely inside aluminum cup
• Steel Washer (2” Diameter x 1/8” or 1/16” Thick) sits completely inside aluminum cup
• Energy Suspension Polyurethane Pad (9.9533G – 1/4” Thick, 88a durometer, square, so had to drill out into discs) sits about halfway in aluminum cup and halfway out
• AMT-provided Delrin Disc (~1", I think) sits completely out of aluminum cup (obviously)
• Energy Suspension Polyurethane Pad (9.9533G – 1/4” Thick, 88a durometer, square, so had to drill out into discs) sits about halfway in aluminum cup and halfway out
• Steel Washer (2” Diameter x 1/8” or 1/16” Thick) sits completely inside aluminum cup
• FlexSeal (thin layer for washer to sit in) sits completely inside aluminum cup
• AMT-provided Vulcanized Rubber Disc (~1/2” Thick) sits completely inside aluminum cup
• AMT-provided Maroon Aluminum Cup

I think the total uncompressed height of the finished product was about 92mm, but given the materials I chose, I don't think it's going to get very squishy anytime soon.

The difference with the mounts installed was definitely noticeable, but certainly not harsh at all in my opinion. An additional caveat is that I did a ton of other work which also stiffened my car up, so it’s hard to say exactly which specific aspects of NVH were directly correlated to the engine mounts, but I didn’t get any additional rattles, etc., and really think that they just made everything feel so much sportier/tighter, and I’d 1,000% do it again (well, I wouldn’t want to go through the exploratory process again, but I’d definitely install the finished product again).

The AMT Vulcan mounts were $250, but I don’t know what my total spend was because I ended up purchasing a bunch of other stuff, some of which I needed and some of which I didn’t (but will keep for other future projects). However, with the final list above, someone could probably come up with a quick tally if they were so inclined. Knowing exactly what to buy, it shouldn't cost very much.

Some additional notes: Some of the Energy Suspension pads didn’t work well because they were too soft under load (9.9528G – 70a durometer; 9.8101R – don’t know durometer, etc.) and would deform significantly upon compression (even just torqueing the nuts). I used the stainless-steel washers inside of the maroon aluminum cups because they had smaller I.D.’s than the I.D. holes inside of the maroon aluminum cups and gray Delrin spacers (which again had M12 I.D.’s), so they keep the bolts centered in place better than just the FlexSeal and/or Energy Suspension bushings (which also had M10 I.D.’s). I chose the Flex Seal liquid over the Loctite PL to fill the gap between the M10 bolts and M12 holes because of its higher temperature ratings (FlexSeal = 350°) and a few other factors. I initially wrapped the mounts in reflective heat wrap but ended up removing it because I didn’t think it was really necessary and also didn’t think it would hold up well against all of the flexing of the mounts over time.

As usual, I’m being really longwinded, but I just thought some of you folks might have some interest in additional (sportier and hopefully a lot more durable) engine mount options for our cars. I don’t know if they help the engine put more power to the wheels, but I’ve read that they’re supposed to. I’m sure there’s a ton of stuff I forgot to include, but if you have any questions, I’ll do my best to answer.

As always, please perform your own due diligence before doing anything like this. Your experience may be different than mine based on countless variables, and I don't want villagers running after me with torches and pitchforks. That being said, I really do think it's a winner. My car is currently sidelined while I wait on parts (Welsh Enterprises - grrrrrr...), and if anything changes my opinion when it finally gets back in the fast lane, I'll definitely update this thread.

Here're some pix so you can see what I've been babbling about:


Above Pic: AMT Vulcan Mounts Upon Delivery


Above Pic: Dimensions Without Aluminum Spacer


Above Pic: Maroon Aluminum Cups with Vulcanized Rubber Discs Inside and Delrin Disc Outside


Above Pic: FlexSeal inside of Maroon Aluminum Cups' and Vulcanized Rubber Discs' Holes


Above Pic: Stainless Washer Sitting in Cozy FlexSeal Bed


Above Pic: Turning Energy Suspension 9.9533G Square Polyurethane Pads into Discs


Above Pic: AMT Vulcan Customier-Custom Engine Mounts Installed on my XFR


​​​

 

Wow what a thread. I would love to do something like this.

 

Thanks. Like most things, figuring out the design and appropriate measurements (especially under load), and then tweaking (and then retweaking, and then retweaking, etc.) them for the desired effect was the really hard part. Actually assembling the final product and installing them was super easy.

 

I am curious to see how your car does after you are back in the road, especially when the engine is under load. I wonder if there is a way to do poly transmission mounts also.

 

I drove the car hard for about 30 miles and it felt great. Then, the water pump went kablooey.

I'm sure there's a way to figure out a poly trans mount, too, but I was so burnt out on doing so much that when I installed a new OEM trans mount right after the custom engine mounts, I just injected the gaps of the trans mount with Loctite PL Roof and Flashing Polyurethane Sealant to help stiffen it up. I did the same thing to several of the new OEM control arm bushings (the ones for which PowerFlex didn't make alternatives). It all felt awesome. After driving my Audi S3 (stage 2+) for years with sport springs, mag ride dampers, aftermarket engine and trans mounts, poly and aluminum inserts for the trans, subframes, etc., when I got back into my XFR, it felt like a wallowy boat (obvious exaggeration), so I decided to go all nuts and tighten up as much as I could, within reason (including all new control arms and included bushings, every PowerFlex bushing they make to replace the new OEM versions, new ball joints, Spires springs, etc.).

 

Very nice mounts! In older high powered cars it was common to add a short length of chain or steel cable to prevent large engine movements. This allowed you to use somewhat soft engine mounts but the chain kept the engine from torquing over and breaking anything. Kind of a cavemen type of mod I guess.

I see the factory mounts have a fabric strap of some kind too?
.
.
.

 

I did a ton of reading on mounts while coming up with these, including a lot on the old American muscle car forums, etc., and they tried all kinds of chains, completely solid mounts, etc. The single bolt design of these removes the need for chains, etc. The consensus seemed to be that the more solid the mounts, the more power was making it to the road, rather than being lost through chassis vibration, etc. But, especially in those older cars, the NVH was nearly unbearable as they became increasingly more solid, and people usually only dealt with it for racing purposes. I was aiming for something tighter than OEM which would be me durable, could better accommodate any increase in engine vibration through performance modification, be easier to install, easy to soften/stiffen up, and prevent the engine from flopping around, but still not rattle my fillings out.

The fabric strap on the OEM mounts appears to only exist to keep the rubber hat from coming off of the mount.