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One forgotten detail about the REAR rotor size increase (which has z direct implication to the upcoming front brake mod... The repositioning of the caliper on the driver's side caused the brake hose to be pulled tight when the suspension was fully extended. To remedy this, I used a brass fitting that I found in my tool box and a longer bolt that I also had.  The fitting had an inner diameter that fit the bolt without slack and the outer diameter was large enough to be a good foundation for the brake hose bracket. This homemade spacer returned enough length to the hose that it no longer made contact with the frame during full suspension extension. 

0731171553.jpgOn the front, I'll be able to use the Eldorado brake hoses with the 14" rotors by making a spacer for the hose bracket that attaches the middle of it to the strut. (see picture of the FRONT strut brake hose bracket bellow)

0731171840-1.jpg

 

Edited by CadVetteStang

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I removed the factory strut tower brace. Note that one of its mounting bolts is also an upper strut mount bolt that protrudes through a slotted hole. Its rearward mount is a stud that is pressed in from bellow.  

0731171851.jpg

I will not be using the factory mounting holes and this slotted hole presents a small challenge since there would not be enough surface to press in a stud. I'd like to avoid a bolt from the bottom side if possible because it will be hard to reach from bellow..... I THINK I have some hardware onhand to solve this, but I want to find my new mounting locations for the strut first.


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I marked the stock location of the strut shaft nut with tape putting it "in the crosshairs". To obtain success in gaining positive caster and negative camber, the new strut shaft will have to be located within the rear inboard quadrant of the crosshairs.

0731171853-1.jpg

 I removed the front struts.... Looking at the strut tower from bellow, you can see the large flat circular area that I have to work with.

0731171857-1.jpg

I'll disassemble one of the salvage Deville strut mounts and drive out the studs so that it becomes a jig to locate the new mounting holes.

Edited by CadVetteStang

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For reference, here is a pic of the factory Eldorado strut in the front strut tower. That giant coil is over 7" in diameter. If I was to use the Eldorado/Seville FE3 "sport" springs, there would not be much room to reposition the mount for camber/adjustments.

0731171839.jpg

However, at this time, I see no reason that the Grand Prix strut could not be mated with the stock Eldorado spring and mount if desired, since the bottom of the Eldorado spring is very close in size to the Grand Prix spring.

Edited by CadVetteStang

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Here's a side-by-side comparison of the Eldorado front strut and the Grand Prix Comp G strut. The GP strut is about 1.25" shorter than the Eldorado strut which is perfect for a slightly lowered car. Also, due to the way the upper Cadillac mount is different by design, I have to use a 3/4" spacer with it. I can install the spacer bellow and keep the 1.25" reduction, or above making a 2" length reduction. (more on that later).

0805171754a-1.jpg

 


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Note 1: if a shorter strut is not desired, the KYB struts that I bought for my wife's 04 Grand Prix GT (FE2 suspension) is longer than the AC DELCO Comp G model (FE3 suspension). I'm not sure if that is a brand difference or if the GP's FE3 suspension is shorter.

Note 2: the Cadillac FE1 option that my Eldorado came equipped with is the "soft ride" suspension, which by comparison is a softer ride than the Grand Prix FE1 suspension offered in it's base model, so even going from an Eldo FE1 to a GP FE1 is a slight performance improvement and would be a noticeable "sporty" ride improvement. The naturally aspirated Grand Prix GT came with their FE2 suspension tuned for a sporty ride feel, which would be 1 step more sporty than the Grand Prix base model and 2 steps more sporty than the Eldorado base model. The next step up in a sportier ride is the V8 Grand Prix GXP which came with the expensive Bilstein (FE4) struts and are cosidered by the Pontiac performance fans to be more luxurious and softer than the FE3 competition tuned suspension offered in the supercharged GTP and GTP Comp G cars. The Comp G has stiffer springs than the GTP and maybe a slightly larger sway bar, but the same front strut.

I made sure to get the AC DELCO brand in order to properly duplicate the factory tune of the competition strut which is what the Pontiac performance fans do when building a Grand Prix for autocross.

Note 3: the Grand Prix strut swaybar tab is welded to the back side of the strut tube unlike the Cadillac swaybar tab that wraps around the front. This will give be more tire clearance.

Note 4: I may mount a tab extender to the backside of the GP strut if the end result has the swaybar end links leaning forward. I won't know for sure what length to make the extenders until I know how far rearward I can mount the top of the strut for a caster gain.

Note 5: BMW's secret to making a front suspension handle well is to lean the struts rearward at the top so that the caster causes the tires to lean in during cornering effectively creating a variable negative camber effect.

Note 6: the GP swaybar tab is higher up on the strut tube and is why the GP end links are longer. Due to strut angle, this is actually an improvement by bring the force closer to the center line of the spring giving a thinner swaybar the functionality of a thicker bar.

 

 


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You should offer kits when you get all the parts sorted out and tested on your car.


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Yes, I was Jims_97_ETC before I changed cars.

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1 hour ago, Cadillac Jim said:

You should offer kits when you get all the parts sorted out and tested on your car.

I would like to, but I suspect that the market for that faded out 10 years ago.

However, if I do work out an LS4 swap built with 585 hp LS2 specs and can retain all instrument functionality, the car will be dubbed the "Carson GT" and I might try to market the whole package at some crazy high price, LOL! 

 

 


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You would need more radiator for that much output, and a separate transmission cooler plus a special build of the transmission, be it the 4T80E or the transmission from the LS4 donor car.  Tire size and clearance will again rear their ugly heads when you balance the chassis for the added power.


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The LS4  FWD car's transmission is a heavy duty version of complete crap. When the drag racers turbocharge or supercharge one of them into the 600-900 hp range, they build a Caddy transmission. 

but the external Physical dimensions of the LS4 is smaller than the Northstar and it weighs about 150 lbs. less, so yeah. I'd have to cut the front springs a little to level it back down and the ride up front would get even more firm because of less engine mass to resist the existing spring force and dampening plus the added spring rate of the extra cut. It might call for a softer spring to replace it since a ride that is too harsh will skate out of turns when the road is not smooth.

But since the Eldorado's nose is about 190 lbs. Heavier than the Grand Prix anyway, the weight would become more like the GP and I might be able to use lowering springs tuned for the GP.

If I ever build a 93 base Eldorado with the 4.9, i'll be dealing with engine weight almost the same as the LS4, but would have to get the Northstar car's transmission because i'd add the 04-08 Grand Prix GTP supercharger to a custom intake like the guy did with the Fiero. And the Eldorado transmission from 85-93 is stressed out at 200 hp.... Yet, I can get a posi front end for those.... 

I actually want to build a 93 for short track autocross where 30-60 MPH is the norm and use my 02 for the faster pro-solo tracks and road racing where 80+ MPH is common. 

however, an LS4 Eldorado built with hot cam LS2 specs would be good in both types of events.

 

 


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Here is a side-by-side comparison of the factory Eldorado front coil spring and the Thunderbird IRS rear spring that will swapped in. The swap spring's dead coil and an additional half-coil were cut off prior to this photo.

The Eldorado spring is a variable rate spring and I have not been able to find the actual factory rate range; however, stock replacement springs in the aftermarket world are rated 135 lbs. per inch.

Same story on the Thunderbird factory springs that I got from salvage. Unknown exact factory rate, but the aftermarke replacements are 416 lbs. per inch. After cutting, they should be in the 500 lb. per inch range- but that is a guess. I left the variable rate coils at the top of the spring to preserve as much streetability as possible.

0805171747c-1.jpg

The springs are tuned to work by different methods. The Eldorado FE1 soft ride spring is very tall and relies on a lot of pre-load to support the weight of the car. It can then "float" on the low spring rate.

The Thunderbird spring will have little pre-load and will have a firm ride that is made tolerable by the top two coils.


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Video: cutting coil springs... I developed a fast and safe way to cut coil springs. The process takes only a few seconds and does not heat up the water to an instant boil when you submerge it.

I installed a metal cutting blade on my 7.5" circular saw and stood the spring upright with a piece of 1×6 board that I tapped into place with a hammer. I then stand over it using my foot to secure the spring. This allows the quick transfer to the cooling water. The board also suspends the warm end of the spring above the bottom of the bucket to prevent melting at the touch if it does get hot and it puts the warm end deep into the cooler part of the water. The cut end of the spring can be handled quickly. The metal integrity of the spring is not damaged.

 

The only drawback is that you can only cut one coil at a time, but the cuts are so easy that it is not a problem. 


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My dad's shop of the 1950's used a 2.5 meter tall press/cutter to cut springs.  Everybody called it the Big Dog.  It was designed for leaf springs but had bits for coil springs.  We used it a lot for making truck springs (big truck springs are never catalog items and are made to spec in the shop that installs them).  We also used it for repairing automotive and small truck springs by making new leaves to replace broken spring leaves, etc.  A separate operation, usually involving a big hammer and a special anvil, was used to adjust the spring curvature.  I never saw the Big Dog used for coil springs but I'm sure that it did happen once in a long while.

I like the metal saw better.  It's important that the spring temperature be kept low enough so that the steel temper is not affected more than a few mm from the cut, which is a skill set thing that you demonstrated in your video here.


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-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
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Yes, I was Jims_97_ETC before I changed cars.

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Thanks for the complement and the story. 

I was not able to edit my post to add that I use a 7" Dewalt abrasive blade from Lowe's that costs less than $10. 

I also pre-set the blade depth so it goes about 1/4" below the coil and does not touch the coil bellow.

 


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Rebound Bumper: I had planned on  re-using the Eldorado billows & rebound bushings so I didn't buy new ones for the rebuild kit. I didn't like the tall, soft Grand Prix bumper because it was 2.6" tall. It may have worked okay with the GP's poorly designed upper strut mount, but was going to limit too much travel with the beefier Deville design.

(Note: the Grand Prix upper strut mounts are very tall, contain a lot of rubber and are designed so that will undulate before the strut shaft moves. When using stiffer springs and struts, GP owners install "anti-pogo washers" on the top of the mount- held in place by the nut- to lock the excessive rubber in place. I chose to use a well designed upper mount made for a heavier car and for a sport suspension.... Forget the bandaid.)

However, when I disassembled the Caddy strut, I found that the bump stop was rotten and crumbling. I couldn't find the stops without buying the billows and didn't want to invest another $30 buying a set of two when I was sure something else stronger and cheaper was out there somewhere.... I explored at AutoZone with the help of someone who took an interest in the project and chose Radius arm bushings for an 80's F250 Ford Truck. I had to order them to get polyurethane. I wound up with 4 useable pieces (enough to build two racing Eldos) for half the price. The  size and fit is PERFECT!

0808171713a-1.jpg

0808171715a.jpg

Above: the Grand Prix strut shaft diameter is smaller than the Caddy strut shaft. The Ford F250 Radius arm bushing fits in such a way that there is no slack and no binding. It will remain at the shaft base during operation. It also fits within the Cadillac billows (larger diameter than the Grand Prix's) so that there is no interference.

Below: this is a bottom view of the Deville upper strut mount with the upper spring seat in place.

0808171718.jpg

Below: here is the bumper's fit if the strut tries to bottom out. There is still room for the compressed billows to fit in the spring seat at the top.

0808171716.jpg

Below: the raised area of the bumber doesn't contact the upper mount, in light a bottom out scenario, but it does reach far enough through the strut bearing that it might make contact with the upper mount in a hard bottom out event provinding some crush protection to the spring seat by transfering part of the impact force directly to the mount (seen in background).

0808171728-1.jpg

Note the black adapter that I made for the strut shaft. It is 3/4" long. More about it in the next post.

Edited by CadVetteStang
adding tech information

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SHAFT ADAPTER: A metal spacer I made to bridge the gap between the heights of the shorter Caddy mount and the longer GP mount....  If positioned below the upper mount (as the picture suggests in the previous post) the Caddy strut mount top would be in position relative to the GP mount and allow full use of the available coil spring area. The overall strut assembly would be approximately 1.25" shorter than the Eldorado strut when fully extended. 

The goal is to have the strut positioned in mid-travel when the car's weight is on the springs. Since the way that I am lowering the car not only involves a 1.25" shorter strut, but also a 1.25" raised suspension (by removing the bushings between the engine cradle (AKA "K-frame") and the body, the actual lowering the car will be a "body drop" in the front that does not effect suspension geometry except for the tie rod angle.(and I might be able to lower the rack to fix that if there is no exhaust system or swaybar clearance issue.

This 1.25"  body drop should not adversely impact the Eldorado's handling.

I will discuss a more dramatic lowering of the car in the next post.

Note: I added extra info in the previous post at the pictures.


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I've been working on how and where to mount the Deville upper strut mounts. To get any noticeable gain in positive caster and negative camber, I had to modify the strut tower openings. This will require a 1/8" steel plate to be used as a reinforcement and to close the gap between the mount and the forward outboard section of the tower. This will also effect the ride height slightly.

I discovered that if I slightly notched the outboard mounting hole, I could use two of the three extsting holes. The inboard is a slotted hole and the lineup is exactly at the back of the opening. This means that my left hand side and right hand side upper strut locations will mirror each other in alignment.

After modifying the opening and verifying the desired mounting position by driving out one mounting stud and sliding the other two into the desired holes, I removed the mount and bolted it upside down on top of the tower and used it as a jig to drill the new hole.

The mount touches the inboard wall  and rear wall of the tower. There is room to slot the new hole for forward movement in alignment adjustments if desired.

0817171935-1.jpg

I'm going to clean up the strut tower modification before I post a photo of the strut mount in its actual position because the unfinished mod looks very rough right now.

NOTE: on the driver's side (shown) there is a black bracket that hangs over the top. I had to chisel off the bung that was welded in place underneath due to a clearance issue. I'll have to move that mounting hole to remount the bracket.

Edited by CadVetteStang

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When the Deville upper strut mount is in its modified location, it leaves a lot of daylight at the forward side of the strut tower opening.

0904171905.jpg

The Eldorado strut towers are very strong, but about 68% of the car's 3800 lbs. Is going to be pushing on the strut mounts that were designed to be supported all the way around. There would be too much flexing of the mount where the bearing needs to glide over a flat surface. I will for sure need adapters to provide a strong foundation for the mounts.


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I used a piece of cardboard to mock up the pattern for the adapter/brace plate.

0904171909c-1.jpg

 


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It's a pretty simple pattern that can be used for both sides (just invert one to make left and right applications).

0904171907_edit_1505516112818.jpg

I just have to plot the location of one 1/2" hole to clear the back of the pressed in stud that mounts the factory strut tower brace and then it goes to one of my friends for fabrication.

Not sure if we will use aircraft grade aluminum or mild steel at this point, but the adapter will be 1/4" thick and that will effect the final ride height.


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I also plan to use two 3/8" bolts in the area away from the upper strut mount to attach the adapter to the strut tower so that the strut does not have to do the work of holding it up tight.


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On 9/15/2017 at 6:02 PM, CadVetteStang said:

 

It's a pretty simple pattern that can be used for both sides (just invert one to make left and right applications).

0904171907.jpg

I just have to plot the location of one 1/2" hole to clear the back of the pressed in stud that mounts the factory strut tower brace and then it goes to one of my friends for fabrication.

Not sure if we will use aircraft grade aluminum or mild steel at this point, but the adapter will be 1/4" thick and that will effect the final ride height.

Edited by CadVetteStang

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Now to build the replacement struts from Grand Prix GTP COMP G, Deville and Thunderbird parts.....

The narrowed section of the Grand Prix is a slightly smaller diameter than that of a Cadillac strut, so to fill the gap, I used these  white nylon bushings that I found in the Hardware department of Lowe's. I did an angle cut on them so that even when expanded, the material covered the full shaft. 

0910171639-1.jpg

Other items could be used to make this adapter, but this was the cheapest and easiest to work with. No real stress will get put on it; its just there to keep the shaft centered during assembly and to keep the top nut from shifting position during extreme vibrations. 

On this strut, I'm placing the Deville upper strut mount on first and putting the spacer adapter on top. This will shorten the strut by 3/4" of an inch. For the other strut, I'll put the spacer adapter on first and compare the two side-by-side and on the car before I determine which configuration I will use.

 


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Here's a side-by-side comparison of the factory Eldorado front strut and the Grand Prix strut with Deville upper mount and Thunderbird rear IRS spring with the dead coil plus one additional coil cut off.

On this strut, the homemade shaft adapter was installed first, then the nylon bushing and upper mount. With the added spring pressure, the strut shaft pulls up some and almost equals the Eldorado strut length.

0910171614a-1.jpg

 


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The strut on the left has the shaft adapter on top of the upper mount. It will limit the suspension travel and keep the strut at the mid travel point if the hight adjustment is around 1 and 1/4" to 1 and 3/4" lower.

Hood clearance could be an issue in this configuration.

0910171710b-1.jpg

Note that I did not install the billows. This is so that I can measure strut travel between the two configurations after the weight of the car has been added.

I'm installing one each initially and will record the data.


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