Quattroporte III 1982 4.9 shock abosrber and bearings

Discussion in 'Maserati' started by Villaadriatica, Nov 6, 2020.

  1. Villaadriatica

    Oct 17, 2020
    Would anyone know and help with my Maserati QPIII 1982 4.9 automatic, I need to change:

    1) Front shock absorber (pair), 330402400 ?;
    Exchange/repair/return of the old ones or just new.
    2) rear right bearings ANT 93550, CSC 93548, CSC 93549, ANT 57793.

    Is there maybe a SKF replacement or someone knows the measurements?

    Any known replacement parts list for the QPIII?
    Thank you for your help.

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  3. GLB

    GLB Formula Junior

    Oct 27, 2010
    Dallas, TX
    Full Name:
    George Lawrence Brantingham
    RockAuto shows SKFJLM506849 for the inner and JLM104948 for the outer. SKF's website confirms the numbers and gives dimensions. RockAuto has other brands, too - must be a common size.
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  4. Villaadriatica

    Oct 17, 2020
    Thank you so much GLB.
    Any idea for the shock absorbers? Best from Croatia!

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  5. Mexico074

    Mexico074 Formula 3

    Aug 14, 2008
    Harriman, TN USA
    Full Name:
    Michael Demyanovich
    Hello Villaadriatica...

    Take a look at, categories, quattroporte III, suspension + steering, suspension... You should find a complete
    set of springs with integrated shocks... I believe these are the exact same as on, but appear to be a bit
    less expensive...

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  6. Villaadriatica

    Oct 17, 2020
    Thank you Mike!

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  8. jamespeter26

    jamespeter26 Karting

    May 9, 2019
    Rome, Italy
    Full Name:
    I will be publishing soon an article which may be of interest to you, stay tuned
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  9. jamespeter26

    jamespeter26 Karting

    May 9, 2019
    Rome, Italy
    Full Name:
    Dear fellow QPIII enthusiasts,

    I was planning to create a new thread about this but I’m actually glad to post this as a reply to someone else’s, hoping that my experience can be useful to others. This write-up is to share my experience in upgrading the front suspensions of my Maserati Quattroporte III. This topic has been discussed in the past and I hope to make a useful contribution for those who may be interested in this.

    I have no affiliation whatsoever with any of the suppliers mentioned in this paper, the point of which is only to share technical information, specifications and measurements. I have no doubt that the solution I’m outlining could be implemented with parts manufactured by other vendors than those I ended up using.

    I am thankful for the technical inputs I received from Verell (Unobtainium Supply), Woods on this forum and QA1. I also want to acknowledge the tremendous amount of knowledge and expertise available on this forum, in particular from Birdman who published a similar procedure for his Ferrari 308.


    The front shock absorbers on the Maserati Quattroporte III are often regarded as a weak point, especially in a car in which most other systems are over-engineered.

    This is due to historical reasons. In what appears to be a cost-savings effort, Maserati’s new owner Alejandro de Tomaso borrowed the overall design of front suspensions, and some components, from his DeTomaso Pantera (a much lighter, rear-mid-engine car), to be re-used in the Maserati Kyalami. Since the Kyalami largely served as a basis for the Quattroporte III, the same design ended up in the QP III as well. The double wishbone configuration is sound and effective, but any given set-up just does not perform the same in a 3,100-lbs sports car and in a 4,400-lbs luxury sedan. In addition, the original shock absorbers (Ariston) appear to be an average-quality version of higher-end Konis. In a word, the original shock absorbers were under-engineered for this car. The experience of fellow owners and mine confirm that the weight of the Quattroporte III is putting too much stress on the shocks.

    As a result, front shock absorbers wear out quickly, usually within a few years from new, and then slowly die after years of under-performance. If never replaced, they are often in bad shape after forty years of duty.

    I refer you to the following if you want to read more about this issue:

    Available options

    When it comes to replacing front shock absorbers in a Maserati Quattroporte III, there is no obvious solution or clear best option. The possibilities fall into three main categories (as indicated here
    1. New OEM shock absorbers (Ariston brand) cost $1,000 to $1,300 for both shocks with springs. Pros: this is the only option that preserves originality. Cons: from an engineering standpoint, this is not an ideal solution, since it consists in replacing a weak part that has failed with an equally weak part which is likely to fail for the same reasons, instead of addressing the underlying problem that caused the failure in the first place. Owners have reported fast attrition when using OEM parts. Shocks should not be regarded as wear parts that need to be replaced every so often – this would be costly.

    2. New shocks by MIE. A few years ago, MIE has developed new, stronger shocks, supposedly addressing the issue encountered with the original ones by using a stiffer spring rate. Pros: they probably last longer than Aristons. Cons: they lift up the front end of the car higher than the rear, which gives an odd, nose-up stance to the car. By the time I am writing this article, these shocks were no longer available on MIE’s online catalog, while Ariston shocks are available, so they might have discontinued this product.

    3. Custom shock absorbers tailored for this car. A few owners have gone this way. Some have been using Koni shocks, which are very similar to the Ariston and represent a conservative middle-ground between originality and upgrade. William Abraham and Thor/Quattroporte3, from this forum, have turned to Aurok Engineering in the UK and developed custom shocks using Öhlins racing parts. According to them, the result was fantastic. These shocks were not only adjusted for the weight and configuration of this car, but also made of much higher-quality components. Pros: you get quality. Cons: quality usually comes at a cost. Öhlins suspensions are expensive. And are not original, needless to say.
    I did not want to go with option 1 or 2 because I felt whatever I paid, I would get poor value-for-money. In addition, I am not an originality freak, especially for functional and non-visible components. Option 3 sounded appealing but pricey. Unfortunately, Aurok has now closed, both William and Thor have sold their cars, and despite my efforts to investigate their exciting endeavor, I was unable to collect enough technical information.

    This write-up describes my own attempt at developing custom front shock absorbers for this car, at a reasonable cost, and without sacrificing quality.

    Key specifications of the original set-up

    The below dimensions were taken from my car with the original Ariston shocks. While they were no longer up to the task in terms of absorbing shocks, the overall stance and ride height was satisfactory in my view. The car was perfectly horizontal and not sagging, so I’m inclined to think that the geometry was correct at least when the car was at a standstill. D1 and D2 were measured directly on the disassembled A-arm, after I removed from the car to be repainted. These dimensions can be used as a baseline as they are probably close to factory specifications.

    Figure 1 – Key dimensions of the original set-up
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    A = Shock absorber angle relative to vertical, at normal ride height ≈ 22 degrees
    B = Shock absorber angle relative to lower A-arm, at normal ≈ 64 degrees
    C = Length of shock absorber from lower eyelet to upper eyelet, at normal ride height = 370 mm or 14.57 inch
    D1 = Distance from lower A-arm pivot point to the shock absorber mounting point = 260 mm or 10.24 inches
    D2 = Distance from lower A-arm pivot point to ball-joint axis = 300 mm or 11.81 inches
    E = extended length of the shock absorber with springs installed: 420 mm or 16.54 inches
    W = corner weight with driver ≈ 532 kg or 1,172 lbs (as specified in the car’s manual, I did not actually weigh the car)

    Figure 2 – Extended length of the original Ariston shock absorber, with spring installed

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    Required parts

    a. Dampers

    Dampers come in a variety of sizes and adjustability from many brands. Öhlins is the best you could get, but qualitative options include KW, Koni, QA1 (formerly Carrera), among others.

    QA1 parts have garnered very good reviews from classic Ferrari owners on Ferrarichat, and little to no negative feedback. They are particularly successful among the Ferrari 308 community here. Also, they are affordable and appear to deliver good value for money, so I decided they would probably be good enough for me. I use my Quattroporte as a daily driver around town and for week-end trips and I am primarily interested in comfort and safety.

    Most manufacturers (including QA1) offer various options in terms of damper adjustability, typically including:
    • Non-adjustable: compression stiffness and rebound stiffness are factory-set and cannot be adjusted (no knob on the shock)
    • Rebound adjustable: compression is fixed at a relatively soft setting, and rebound is adjustable from soft to stiff (one knob on the shock)
    • Single adjustable: both compression and rebound are adjustable using the same knob, but this may end up in having an excessively stiff compression if you need stiff rebound
    • Double adjustable: compression and rebound are adjustable using two separate knobs, mostly used for track applications, often needs a lot more fiddling to find the correct settings

    One of the things I liked about the Öhlins shocks developed by William and Thor is the fact that damping was adjustable. When it comes to damping characteristics, one cannot calculate and simulate everything on paper, and expect to obtain exact results in reality. Unless you already know your exact damping requirements from an earlier experience with adjustable dampers, non-adjustable dampers will, at best, give you the feeling of “it could have been perfect but there’s this small thing I don’t like and there’s nothing I can do about it, except replacing the dampers again”. That’s why you need adjustable shocks.

    I decided to go with the “rebound adjustable” option, because in a typical street car, compression needs to be relatively soft and rebound somewhat harder. I preferred this option over the “single adjustable”, because the latter does not offer independent rebound and compression valving: increasing rebound stiffness will increase compression stiffness at the same time, and the proportionality between rebound and compression is fixed. In “rebound adjustable” and “double adjustable”, compression and rebound settings are independent from one another.

    In hindsight, I probably should have ordered “double adjustable” and I may end up doing that in the future, because I feel that compression damping is a little bit too soft.

    The QA1 product range reads as follows:
    • Non-adjustable is called “Aluma Matic”
    • Rebound adjustable is called “Ultra Ride” (product reference prefix: US)
    • Single and Double Adjustable are called “Proma Star” (product reference prefixes: DS and DD)
    All of them come in various sizes, measured in compressed and extended length from eyelet to eyelet. It is good practice to remain around the middle of the travel range at normal ride height, and to maintain a minimum of 2.5-3 inch of available travel in compression and 2-2.5 inch of travel in rebound.

    With this in mind, and the above measurements, we know that we are looking for a damper of the following dimensions:
    • Compressed length: 11.6-12.1 inch
    • Extended length: 16.6-17.1 inch
    An important point is that QA1 shocks are adjustable for pre-load, meaning that it is possible to adjust ride height once the spring is installed on the damper. This means that we can adjust preload to achieve ride height at the middle of the damper stroke. Assuming that we will adjust the preload to get a spring length of 14.6 inches at normal ride height, the below table illustrates available options from the QA1 catalog:

    As is clear from this table, the US/DS/DD 502 size is the correct option in our case. It is actually very close to the original shock, which is good. Other brands probably offer similar options, but it shouldn’t be difficult to find a suitable size.

    b. Mountings

    QA1 dampers offer three mounting options:

    • Bushings, comprised of metal eyelets at each end of the damper, a polyurethane bushing inside the eyelets, and an inner metallic sleeve inside the bushing (for the mounting bolt)
    • Bearings, with no polyurethane or rubber parts – this reduces comfort but increases geometric precision and is preferred for racing cars, probably not an ideal choice for a large sedan like this one
    • Studs

    The Quattroporte III requires bushings on both ends of the shock absorber.

    However, even with bushings, QA1 dampers won’t be plug-and-play. QA1 bushings are imperial and Maserati uses metric bolts. QA1 bushings do offer a 0.5-inch internal diameter metallic sleeve for the mounting bolt, or approximately 12.7 mm, but our mounting bolts are metric 12 mm in diameter. The 0.7mm gap means the bolt will be loose, and this kind of looseness in a 2-ton car is very likely to cause breakage and suspension failure. Not an option.

    There are two possibilities, a good one and a bad one:
    1. Drill the lower A-arm and chassis mounting holes to 0.5-inch diameter and use imperial bolts instead of the original 12 mm. That’s the wrong option, not only because it is an irreversible modification to the car’s originality, but also because unless done professionally, it will most likely end up with slightly misaligned holes which are not safe and will increase stress on the shock and A-arms.

    2. Adapt the dampers bushings to accept metric bolts by using a metallic sleeve with an outside diameter that fits in the QA1 imperial polyurethane bushing, and has a 12 mm internal diameter for the bolt. And that’s where we are happy to be on a Ferrari owners, because they designed a brilliantly elegant solution to do exactly that.

    There’s a small company, called Unobtainium Supply Co., which makes NLA parts for classic Ferraris. A few years ago, they engineered a special bushing adapter to install QA1 bushings on Ferrari 308 mountings, which does just that. So this is exactly the part you need, and if I may add, Unobtainium Supply products are remarkably engineered. The thicker sleeve wall means it will also better prevent the bolt from bending. I’ve read somewhere that they may also be suitable for Varishock dampers and possibly more brands, but I cannot confirm this.

    For more information and pictures on this product, refer to .

    Ferrari 308 shock eyelet bushings cross-reference the Maserati Quattroporte III’s bushings, as it is clear from the product specifications sheet on MIE’s website (see below). They have a M12 internal diameter, and 46 mm internal diameter length (corresponding to the width of the mounting bracket, on the chassis and lower A-arm).

    Figure 3 – Dimensions and cross-referencing of the original shock absorber bushing

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    Source: Screen capture from MIE’s website, May 6th 2020.

    Verell Boaen from Unobtainium Supply Co. was kind enough to confirm that his bushing adapter sleeve is indeed designed M12 and 46 mm long, making them suitable not only to our cars, but also probably to several other cars of the same period, including the DeTomaso Pantera, Maserati Kyalami and Quattroporte III (perhaps a few more), and Ferrari 246, 275, 330, 308, some 328, 365, 512bb. This is, in fact, a versatile piece of engineering.

    While these bushing sleeves are a perfect fit for the front shocks, the rear set-up is different and Unobtainium’s bushings won’t fit, so there is no point in ordering more than 4 if you are planning to do the rear as well. Verell normally sells the bushings in a 4-wheel set (8 bushings total) but he was kind enough to take my order for a 2-wheel set.

    c. Springs

    QA1 shocks use 2.5-inch internal diameter springs, which are very common and come in all spring rates, making it easy to swap springs if the rate is not correct.

    Based on my measurements, the QA1 tech team calculated that the required spring rate is 425 lbs/in, and suggested that I could go with 400 lbs/in for a soft ride, 450 lbs/in for a stiffer ride, and that I could even use 500 lbs/inch if I wanted a sporty ride.

    The first spring rates mentioned by Thor/Quattroporte3 while developing the Öhlins set-up were a bit lower, around 300 or 325 lbs/in, but he indicated that they were probably a bit too soft for his car and that he would switch to stiffer springs. However, he did not specify the final spring rate he ended up with.

    Based on these inputs, I decided to go with 400 lbs/in. This is a good fit for the car, the shocks don’t bottom out even on big bumps or at high speed, and the ride is smooth without being mushy. Again, in hindsight, I think I would have preferred 425 lbs/in because it is ever so slightly softer than I like, but nothing problematic at all. I therefore consider that 400 lbs/in represent the softer side in a range of acceptable options, and I wouldn’t recommend going lower than 400 lbs/in. Spring rates aren’t an exact science and more than one rate usually works with a particular car.

    d. Accessories

    There are two important accessories that have to be purchased separately:​
    • Rubber bump stops, to avoid damaging the damper in case you bottom-out the shock absorber. QA1 offers a few options but you need the sturdy BC02 bump stop, which is 0.875-inch long and 1.9-inch wide. At less than $7 apiece, it’s a cheap way to be on the safe side.
    • Roller bearings (aka thrust bearings) make spring pre-load adjustments a lot easier. They were highly recommended by the QA1 tech team as well as many Ferrari owners. Since you will need a special spanner wrench to adjust pre-load, you can purchase a kit with spanner wrenches and roller bearings for 2 shocks.
    My final parts list was:

    (2) QA1 US502 Ultra Ride dampers (11.625” compressed length; 16.875” extended length) – $339.90

    (2) Eibach EIB1200-250-0400 springs (12.00” length; 2.50” diameter; XXX lbs/inch rate) – $140.00

    (2) QA1 7888-110 Ratchet Spanner Wrench & Thrust Bearing Kit – $41.95

    (2) QA1 9072-105 Anti-seize lubricant (= Permatex Aluminum Anti-Seize lubricant) – $5.98

    (2) QA1 BC02 bump stops (0.875” length; 1.9” O.D.) – $13.98

    (0.5) QA1BUSH bushing kit from Unobtainium Supply Co. (2-wheel set) – $85.00

    Total: $626.81 – This is almost half the price of a pair of Ariston shocks!

    (more to follow)
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  10. jamespeter26

    jamespeter26 Karting

    May 9, 2019
    Rome, Italy
    Full Name:
    #8 jamespeter26, Nov 11, 2020
    Last edited: Nov 11, 2020
    Assembling the shock absorbers

    Assembling the shock absorbers is an easy and straightforward task which is well-described and illustrated here and here so I didn’t take pictures.

    The only differences are:
    • You won’t need the extended shock eye which is a special part required for Ferrari 308s
    • You won’t need spring compressors, which are only required with US/DS 402 shocks (the smaller size) but not US/DS-502. When fully extended, QA1 US/DS/DD502 dampers are long enough to install 12-inch springs without having to compress them first. You just need to pull the damper rod, insert the spring, and secure it in place as specified in the instructions sheet.

    Inserting the Unobtainium metal sleeves requires a bit of effort and can be done either before or after installing the springs. It can be achieved with hand tools but not with a hammer. In the absence of a hydraulic press, I used the “bolt method” whereby you press the bushing in by using a bolt, a nut, a couple of large diameter washers, and two wrenches. I didn’t take pictures but this is a rather common procedure – see or

    Once the shock absorber is fully assembled, I found that the best ride height is obtained by pre-loading the spring by 1 inch, that is to say, tightening the spring seat to compress the spring until it is exactly 11 inches long.

    At this stage, it is a good idea to measure exactly the ride height of your car before removing the original shocks, and determine your target ride height (same or higher if your car is sagging). This is done by measuring the distance from the ground to the top of the wheel well, on a vertical axis that goes through the center of the wheel. In my car, this was exactly 69 cm or 27.2 inches and I think it wasn’t sagging.

    Adjusting the preload up or down will allow you to determine ride height once the QA1 shocks are installed. In my car at least, a 1-inch preload produced a 27.2 inches ride height.

    Installing the shock absorbers in the car.

    This is a straightforward process. You will need to remove the wheels and put the front end on jack stands.

    For those who don’t use jack stands often, it may be useful to remind that using jack stands can be dangerous if done improperly, so please get familiar with the essential safety procedures associated with jack stands, watch videos, and use the appropriate tools.

    This suspensions job won’t require to crawl under the car and you will be working outside the wheel well, but you should always apply the same safety standards whenever using jack stands, regardless of the type of job you’re doing. I cannot be held responsible if an accident happens because you didn’t respect these essential safety procedures. If you don’t feel safe doing this procedure yourself, leave your car with a qualified mechanic.

    The next step is to remove four bolts: the upper and lower shock absorber bolts, and the two upper control arm bolts (the ones linking the control arm with the car chassis), as described in the service manual. It is not possible to remove/install shock absorbers without moving the upper control arm out of the way, but you won’t need to remove the upper ball joint, so the upper control arm will remain attached to the car and pivot by the ball joint. For information, all these bolts are M12 so they have a hex 19mm head. You will need a ratchet with a 19 mm socket, and a 19mm spanner wrench.

    I recommend unbolting the shock absorber first, then the upper control arm bolts. The two upper control arm bolts and the upper shock absorber bolts are 75 mm long, the lower shock absorber bolt is 85 mm long. You don’t need to remove anything else: the lower control arm, ball joints, knuckle, brakes, etc. can remain bolted.

    Be careful when removing the final bolt from the upper control arm: the whole suspension will fall under its own weight, including the wheel bearing, brake calipers, etc. and the upper control arm will rotate freely since it is attached only via the lower ball joint. One thing you don’t want to happen is to let it hang, because this will pull on the brake line and damage it. So be ready with a box or piece of wood under the lower control arm, to ensure the whole assembly remains supported and won’t hang on the brake line. Note that the knuckle assembly, brake caliper and brake disc are rather heavy.

    After unbolting the upper control arm, rotate the upper control arm 180 degrees around the ball joint, so that it is now facing outwards. This will clear the shock absorber, which can now be removed from the car. You may need to pry a little bit.

    When mounting the new shocks in the car, you will have to bolt the shock absorber lower and upper bushings first, and then rotate the upper control arm back in place. Due to the QA1 shock absorber being slightly longer than the original shock, you will be able to insert one of the upper control arm’s bolts, but not the second one because the holes won’t align.

    Figure 4 – With the new shock absorber in place, one of the control arm
    bushings does not align with the mounting bracket (on the left)

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    After bolting the two shock absorber bolts, bolt one of the upper control arm mountings to the chassis. At this stage, the shock absorber will pull down the whole suspension a bit too much, making it impossible to align the second A-arm bushing with its mounting bracket on the chassis.

    You will need to jack up the lower ball joint just enough to align the second upper control arm hole into the mounting bracket, which is half an inch or so. Once this is done, you can insert the bolt and then un-jack the ball joint.

    Figure 5 – How to jack up the suspension from under the lower ball joint

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    Figure 6 - After jacking up the suspension, the upper control arm is aligned
    with the mounting bracket and the bolt can be inserted

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    with suspensions, DO NOT torque the bolts until the car is lowered at normal ride height. Put the wheels back, remove the jack stands, the jack, and then torque all bolts as specified:
    • 12 Kgm or 86 ft-lbs for the three 75 mm bolts (upper control arm and upper shock absorber mounting)
    • 10 Kgm or 73 ft-lbs for the 85 mm bolt (lower shock absorber mounting)

    Check that everything is in order, inspect the brake line to ensure it wasn’t damaged in the process.

    It is important to ensure that the final ride height is correct. If not, jack up the car again and tighten or loosen the spring seats in the desired direction, to increase or reduce preload, then check again.

    Once you are good to go, one last adjustment you will want to make is the damping knob. In general, it is recommended to start at the lowest damping (knob fully turned counter-clockwise) and slowly increase it based on test drive until you reach the desired damping stiffness. It is very easy to turn the damping knob even on the side of the road. I found that the lowest level of damping would make the car sway like a boat. A few clicks made a lot of difference. The sweet spot was at exactly 9 clicks from softest, for me. It took a few weeks to find exactly the correct setting.

    Generally, you want to dampen enough to reduce oscillations to a minimum (i.e. make the shock get back to its normal length as quickly as possible after hitting a bump or a pothole, and reduce the number and amplitude of compression/extension cycles) without dampening too much (which would prevent the spring from doing its job).


    There is no denying that new suspensions are a fantastic improvement in all respects. The car is more stable, more comfortable, it just feels newer and better.
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  11. Mexico074

    Mexico074 Formula 3

    Aug 14, 2008
    Harriman, TN USA
    Full Name:
    Michael Demyanovich
    Hello JamesPeter26....

    Wow !!! Very, very nice work....

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  13. Villaadriatica

    Oct 17, 2020
    Thank you James!

    Sent from my iPhone using mobile app
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  14. jamespeter26

    jamespeter26 Karting

    May 9, 2019
    Rome, Italy
    Full Name:
    Sorry for the multiple posts but I spotted an error and thought I'd rather correct it now for the record. D2 length of lower A-arm from pivot to ball-joint axis is 340 mm, not 300 mm. 300 mm is the length between pivot and 2nd eyelet of ball-joint bracket, but the actual ball-joint axis is a bit further.

  15. Quattroporte3

    Quattroporte3 Formula 3

    Nov 13, 2010
    Excellent work Peter!

    I've been away from the forum for some time, and felt like checking in, quite surprised to see how much research and effort has been put into this, very inspiring.

    I did try and get back in touch with Aurok a few years ago, unfortunately Dave had retired and I can't recall if I ever received any more info from Justyn, it's been a few years. I don't see anything in my notes from that time.

    It's really helpful for all of us to document what we find and how we fix it for future enthusiasts, and I applaud your thoroughness and clarity in how you present your findings.

    Did William ever finish his resto-mod..? He had some interesting ideas as I recall.

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