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Discussion Starter · #1 · (Edited)
First and foremost I just wanted to say I have been a long time lurker soaking up information throughout the forums and been following the 350Z shock thread closely. I just wanted to join to say this project is not a bust and give credit where due to Wile E. I chose Bilstein B8's because they are basically the go to shock for maintaining on street manners whilst being significant upgrade over the stock stuff on multiple platforms (a favorite stock replacement for the S550), it's monotube design, and most importantly the fact it does not have the external stop ring that keeps a MN12 top hat from working so I was able to utilize the MN12 top hat on the 350Z shock with 0 modification to the tophat. I did not have to trim the spring perch as the 350Z LO-Suspension 1" drop springs I chose fit the perches perfectly centered. I did not cut my shocks down and used them as is height-wise. From what I understand from 350Z guys is that the B8 and B6 have similar stiffness but the B8's are engineered for a drop springs without shortening the life of the dampener so I went with those for that reason alone.

List of what was done and used:
  • 03-09 350Z Biltstein B8 Shocks
  • 03-09 350Z LO Suspension 1" Drop Springs (Spring Rate Unknown) **Note: If I had to do again I would use 1.25" drop springs and Lincoln Mark VIII "adjustable coilover" tophats with custom aftermarket perch to drop the front end lower as the only con is the height of the 350Z shocks are taller than the MN12 ones (as documented in the Tien thread). I did not want to cut my $500+ Bilsteins.
  • I did not use the factory cup washers as I noticed the stock tophats used cup washers to cup the bushings down where the aftermarket tophats were already cupped with the sleeve built in as one piece. **Note: If these shock mounts fail prematurely due to not using the cup washers from the original front shocks I am fine with that as that (this is my project car not a Daily) will be a reason to get the thinner Mark VIII coilover tophats and custom perches to drop the front end closer to where I would like. Right now I am not noticing/feeling anything sketchy with the cup washers being gone. I had to eliminate them to be able to get the shock nut on the shaft fully.
  • Took both control arms to the machine shop to get the shock bushings trimmed down precisely so the 350Z shackles will fit the MN12 shock bushings properly
  • Had machine shop also drill the shackles to ensure MN12 bolt properly fits through 350Z Biltstein shackle
  • I am running Lincoln Mark VIII rear LCAs w/ SCP spring perches that fortunately raised the rear of the car to not have an awful "Carolina Squat" and sit closer to stock replacements albeit with much improved handling and bump absorption thanks to the better Bilstein dampers
Other Notes: While doing this project I completely rebuilt the front suspension with quality TRW and Moog Premium-line components not cheap replacement grade stuff with sketchy balljoints, endlinks, and dust boots (car was properly aligned afterwards). New strut rod bushings w/ TBSC steel sleeve/stock bushing kit on frame end + Moog polys on LCA ends. The car has all new wheel bearings/hub assemblies (went ahead and swapped to Mustang/PBR stuff for better wheel choices than FWD stuff), running Cobra IRS hub assemblies in the rear with stock rotors re-drilled by machine shop (I am still using the stock rear disks). I am using Lincoln Mark VIII LCAS in the rear w/ SCP spring perches which luckily raised the rear end higher than the front so the car does not squat. Backseat and sound deadening was removed though you can argue that the seat was not that heavy (the sound deadening was actually heavier once all boxed up) so I am not exactly sure how much clout that has to do with keeping the rear up. I am running Cobra Bilstein B6s in the rear. My overall impressions are: much better braking, nose dive is almost eliminated, turn-in is much better, and last but not least the ride quality is amazing, the car absorbs bumps much better and the 350Z front springs are not "bouncy" or "jarring". I would imagine these are light-years better than any Monroe or KYB OE MN12 replacement and match perfectly with my Bilstein Cobra rears + stock rear springs (non sport). I will be driving the car back and forth to work to test long-term reliability and document anything out of the ordinary. This car may be getting a Coyote/10R80 setup in the future (depending on the whole tuning/EPA fiasco) so I want to definitely make sure this holds up.

Cons:
  • Unfortunately the 350Z shocks are taller and most of us do not want to cut them down so for those with significantly lowered cars (I am fine with stock-ish ride heights), the inserts are still a better option for you as the 350Z front shocks are taller.
  • Besides 1.25" 350Z drop springs and Mark VIII air ride replacement "adjustable coilover" tophats, there is not much you can do outside of cutting (which I highly disagree with) the shock down to drop front ride height. The 350Z shocks are simply just taller than the MN12 ones.
  • Slightly taller ride height is noticeable and might be aesthetically unpleasant to some though it is still fairly stock-ish **Note: Slightly taller ride height did not negatively affect handling in my experience (normal people will most likely not even visually notice)
  • You cannot use the MN12 cup washers on the 350Z shocks due to a shorter shaft **Note: I will be monitoring this for premature wear, so far I feel nothing out of the ordinary nor do I visually see my shock mounts failing prematurely at the moment. The aftermarket shock mount/top hat I used does not use separate bushings that need to be cupped with a washer like the stock shock mounts and is already cupped/one-piece with the sleeve built-in. The nylock nuts that came with the Bilsteins appear very stout. Once the weight of the car is on them they look perfect.
Here are various photos I took of the project, please ignore the anti-seize on the brake calipers, all of that was wiped/cleaned off and replaced with proper brake lubricant. Rear shock tower bar in back is a 95-99 DSM bar I barely had to modify to fit other than drilling the proper bolt holes:

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That ride height is definitely unsettling! I would like to see how it does with cutting a coil off the spring. That might bring the ride height back to a normal level, but it might make the ride too jarring.
 
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Guys, if these fit, there are adjustable konis available for 62.50 each!!!!
 

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I'm just thinking about this. That lower bracket piece doesn't look to complicated to make. Rather than cutting the shaft and welding it shorter, and then having to trim down the bushing on the control arms, it would be fairly straightforward to fabricate a new lower mount that would match the tbird LCA, and then weld it on in the correct location to keep a stock ride height, or even lower it however much you want.
 

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Very great work ! Just wondering if the front shocks travel will be enough if a coil is cut to lower the ride height. It also depends on the spring rate...
 
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I've been thinking, rather than the cut and weld solution to the extention on the bottom for lowered ride height, what about cutting the shock mount off, running a large die on that rod section and using thick U channel as the shock mount secured to the newly threaded section with nuts? Makes it slightly adjustable as well.

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I don’t trust not having the top washer though, it might be fine on the ground but with the suspension at full droop on stands only the edges of the nut and rubber prevent it ripping through the mount.
 

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Discussion Starter · #12 · (Edited)
That ride height is definitely unsettling! I would like to see how it does with cutting a coil off the spring. That might bring the ride height back to a normal level, but it might make the ride too jarring.
I can definitely see how it would not fit the enthusiast look and is a little high for my tastes (though acceptable for now). Rather than cutting a coil (in fear of losing ride quality) I will try other 350Z drop spring options that are around 1.25"-1.3" up front along with these Mark VIII tophats (keeping the tophats and tossing the junky coilovers) with incorporating some type of aftermarket perch that is thinner.

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Im glad theres a way to install them without cutting or welding, though that is very tall. Like mikey said, maybe a higher drop spring or coil cutting can bring it down? But either way, great write up. Glad to see its possible.
Thank you, I could not have done it without your post and would feel terrible taking credit for an idea that was not mine. I will be trying better even lower drop springs in the future along with the tophats above. As of right now I am enjoying the ride quality and reduced nose dive. I enjoy driving this old 4.6 Cougar more than my 10R80 Ecoboost despite being much slower than the Mustang. The upgraded and rebuilt suspension makes it that much more fun even at low speed. These cars were so ahead of their time and wish Ford offered a classier larger coupe today.

Guys, if these fit, there are adjustable konis available for 62.50 each!!!!
That would be a great value proposition, post links if possible.

I'm just thinking about this. That lower bracket piece doesn't look to complicated to make. Rather than cutting the shaft and welding it shorter, and then having to trim down the bushing on the control arms, it would be fairly straightforward to fabricate a new lower mount that would match the tbird LCA, and then weld it on in the correct location to keep a stock ride height, or even lower it however much you want.
That sounds interesting, I look forward to everyone improving on these and other shock options.

Very great work ! Just wondering if the front shocks travel will be enough if a coil is cut to lower the ride height. It also depends on the spring rate...
Preciate' it! Bilstein B8s are meant to take the abuse of lowering springs or lowered springs. Biltstein B6s are really meant for stock or close to stock springs. The only thing I worry about with cut springs is loss of ride quality.

Someone needs to sticky this or move this to the 2021 shocks option thread. A sticky on its own I prefer, because I am looking at a particular shock for me to try next
Do it up man, can't wait to see what other options others try!

I've been thinking, rather than the cut and weld solution to the extention on the bottom for lowered ride height, what about cutting the shock mount off, running a large die on that rod section and using thick U channel as the shock mount secured to the newly threaded section with nuts? Makes it slightly adjustable as well. Food for thought.

View attachment 43185

I don’t trust not having the top washer though, it might be fine on the ground but with the suspension at full droop on stands only the edges of the nut and rubber prevent it ripping through the mount.
The cutting and welding of shocks is a bit too risque for my tastes and out of scope for me but if someone does it successfully I will pay for quality work. Once the top hat had the 3 surrounding nuts in, even without the entire weight of the car the squishy appearance of the mount dissappeared. The squishy appearance only shows when the shock is out of the car (picture of the shock on the table). I could be very well wrong though and they may fail prematurely. So far knock on wood, after taking the car down curvy and slightly bumpier roads the tophats are still looking great and the metal sleeves appear stout. I would prefer a washer myself and even thought of shaft extensions (to allow the use of the cup washer) similar to what Jeep guys use but I question strength there. Trying the Mark VIII coilover tophats would be a start in the right direction for me. I am open to any ideas and glad I could contribute something. I will continue to post updates and even document negative stuff to prevent having others waste their time and money if something fails.

Other notes: As the suspension settles and breaks in I am really enjoying these dampers in the smoothness/NVH department. It makes me want to throw a set of Bilsteins on my Mustang once the stockers blow out.
 

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The cutting and welding of shocks is a bit too risque for my tastes and out of scope for me but if someone does it successfully I will pay for quality work. Once the top hat had the 3 surrounding nuts in, even without the entire weight of the car the squishy appearance of the mount dissappeared. The squishy appearance only shows when the shock is out of the car (picture of the shock on the table). I could be very well wrong though and they may fail prematurely. So far knock on wood, after taking the car down curvy and slightly bumpier roads the tophats are still looking great and the metal sleeves appear stout. I would prefer a washer myself and even thought of shaft extensions (to allow the use of the cup washer) similar to what Jeep guys use but I question strength there. Trying the Mark VIII coilover tophats would be a start in the right direction for me. I am open to any ideas and glad I could contribute something. I will continue to post updates and even document negative stuff to prevent having others waste their time and money if something fails.
Same here I don’t have a welder and don’t really like the idea of putting that much heat on the metal if I did, even if it dissipates some where done, but cutting threads into that section like I illustrated is pretty feasible in both respects, no heat induced and cheap with a little elbow grease.

My concern with the top hat washer stems from me having the car on jackstands for a few months straight where the metal insert in the hat actually separated from the rubber due to the spring force pulling down on the shock, and in effect once I got the car moving again you’d hear the sleeve moving inside the rubber over bumps. Had that washer not been there it’s very likely the nut would have pulled through the rubber at some point while still on stands. I’d be less concerned on the ground but if the front end rises any cresting a hill at speed I’d be very nervous about them pulling through. A custom or modified top mount would be feasible though, Randy was modifying stock ones to use bearings for the 3000gt inserts, and something similar should work here.
 

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I have a couple quick questions. Would drilling into the bottom of the top mount allow for the cupped washer to be used when putting it back together? Also did you have to modify the underside of the upper mount to fit the spring properly, the way the guy who did the Tein setup had to?
 
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Excellent work. Thank you for taking what was out there and already developed and advancing it further.

How is the silver lower spring perch attached to the shock body on those? I don't see any welds on the bottom. I cannot see the top. The overall assembly is quite a bit taller than the MN12 unit, but between reworking the bottom mount and possibly the spring perch it looks like you could get it down to the same height.
 

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Discussion Starter · #16 · (Edited)
Same here I don’t have a welder and don’t really like the idea of putting that much heat on the metal if I did, even if it dissipates some where done, but cutting threads into that section like I illustrated is pretty feasible in both respects, no heat induced and cheap with a little elbow grease.

My concern with the top hat washer stems from me having the car on jackstands for a few months straight where the metal insert in the hat actually separated from the rubber due to the spring force pulling down on the shock, and in effect once I got the car moving again you’d hear the sleeve moving inside the rubber over bumps. Had that washer not been there it’s very likely the nut would have pulled through the rubber at some point while still on stands. I’d be less concerned on the ground but if the front end rises any cresting a hill at speed I’d be very nervous about them pulling through. A custom or modified top mount would be feasible though, Randy was modifying stock ones to use bearings for the 3000gt inserts, and something similar should work here.
The threaded idea is definitely something to think about for sure. I bet it would be cake for my local machine shop to do (I am too afraid to do it lol).

Yes this is definitely not a long-term solution, especially since I want to further reduce ride height. I wish I knew those Mark VIII coilover tophats (I guess I skimmed over them) existed earlier :(. I'll pick up a set after some miles or the first sign of failure of the bushings. The aftermarket replacement tophats are very thick for some reason compared to the stock Ford stuff. I would definitely agree for anyone doing this not to follow me and use a washer and/or a better/modified tophat solution. I'll get some miles on this setup (since everything is aligned perfectly and driving like a dream) then remove the shocks and attempt to incorporate the Mark VIII tophats. I am monitoring the sleeves on the top hats very closely and will document any remote hint of a failure.



I have a couple quick questions. Would drilling into the bottom of the top mount allow for the cupped washer to be used when putting it back together? Also did you have to modify the underside of the upper mount to fit the spring properly, the way the guy who did the Tein setup had to?
That is a good question and I did not think of that. You would have to be careful drilling as you would have to reduce/cut the length of the sleeve as well. You would still be stuck with the ride height though since the mount itself is so thick. I did not have to modify the underside of the upper mount as my spring was perfectly centered and does not appear to be going anywhere. Your mileage may vary depending on the spring you use. I am hoping the car settles more once the mount "wears" down some but despite the heavy front end of the car it looks like that is where it is going to sit without a lower spring and a improved top hat solution.

Excellent work. Thank you for taking what was out there and already developed and advancing it further.

How is the silver lower spring perch attached to the shock body on those? I don't see any welds on the bottom. I cannot see the top. The overall assembly is quite a bit taller than the MN12 unit, but between reworking the bottom mount and possibly the spring perch it looks like you could get it down to the same height.
Thank you, I would have never thought about using another platform's front shocks without the originator of this idea. I am hoping others will improve on this and offer even more solutions. The silver lower perch is "built-in" and the nice thing about it is it rotates (I am guessing with some type of bearing) so it makes installing the spring a breeze without worrying about the indexing of the tophat versus the stationary bottom perch of the MN12 shock. Not having that external bump stop found on other manufacturer's shocks really made this more accessible for me.
 

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I'll be taking apart my Honda suspension to replace the front shocks soon. It's got the same fork as the above pictured RL fork. Though, I don't have any Koni inserts to test.

The problem with using inserts though is that there is no spring perch anywhere. It would have to somehow be affixed to the body of the insert. This part was discussed in either my suspension thread (see my signature) or in the Gunn's Bilstein insert thread.
 
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I have a set of konis for my Contour, and the rears fit in a bracket like that.
 
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I did a quick and dirty proof of concept on this today. I bought the cheapest MN12 LCA and 350z front shock I could find on Rockauto, and decided to try making a new lower mount that would simultaneously avoid having to cut down the control arm, and address the height issue. I ended up with a shock that is 1.25” shorter than the stock 350z one (based on the recommended measurement from the tein thread), and fits the MN12 LCA with no modifications. I welded up the bracket first with the shock not attached, and then welded the shock in place. The shock is also recessed into the mount and welded on both sides for added strength. When welding on the shock itself, I just kept a cold wet rag on it, and even after welding both sides back to back, the temperature on the shock body itself was only 108F, so no real danger of blowing out the shock doing this. I guess now I have to buy some Bilsteins!
 
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