How to do the Guldstrand Mod the "hard way" - Team Camaro Tech
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post #1 of 8 (permalink) Old Aug 4th, 11, 08:20 AM Thread Starter
Join Date: Feb 2011
Location: Oxnard CA
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Lightbulb How to do the Guldstrand Mod the "hard way"

With things down to the frame on my '70 Nova, I decided now would be a good time to address some of the suspension shortcomings that I was fighting at autocross last year. First, it's well documented that the camber curve for 1st gen Camaros and 3rd gen Novas like mine is a bit backwards. There are a host of ways to address this and I decided to do the rather popular Guldstrand mod. As you may know, this moves the upper control arm frame mounting points down a bit to primarily increase negative camber on compression ("camber gain"). If you want to learn more about this, do some searching because it's been discussed in detail elsewhere.

The conventional method for implementing the G-mod is to drill a second set of holes lower on the UCA towers. I've decided instead to do the G-mod the "hard way" by cutting the UCA towers off at their base and welding them in at the new location. I am not the first to do it this way, but information and pictures have been hard to find, so I decided to document the process to help others.

I decided to do this the “hard way” rather than simply redrilling holes because I wanted a cleaner look and a flat mounting surface for the alignment shims. The drilling method has its own advantages too: it is much easier and if you have tubular arms, you can leave the original holes in place in case you decide to go back.

I started by pulling apart the suspension. I supported the weight of the car with a jack near the balljoint on the lower control arm, then loosened the upper balljoint, used a separator to get it to "pop" while the nut was still on the end, then simply loosened the nut until it came loose. There was a little bit of spring energy left when the nut came off, but not much - the car moved up only a little bit. Now I realize this is not safe to do on all vehicles, but in this case it worked out fine. I had left the shock in place just in case things decided to go flying anywhere. Finally I put a jackstand under the front of the frame and lowered the jack to release the spring.

First I used a c-clamp and a socket to remove the studs for the upper control arms.

I then cut a few pieces from 2-1/2 x 1/8 bar

I bought the actual template directly from Dick Guldstrand's shop. You can download copies of it off the net, but I like to support the people that develop these things and this way I was assured I had the “right” dimensions. Here I use a punch to transfer the hole locations to a piece of flat.

After drilling the four 7/16" holes, I trimmed the lower portion of the plate to follow the flat contoured section of the UCA tower. The new location for the rear hole is very close to a curved potion of the tower, so I ground it at an angle on the backside so the plate would sit flat.

Here is the relocation plate now bolted on both sides

Next I made plates that bolt to the motor frame stand locations.

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post #2 of 8 (permalink) Old Aug 4th, 11, 08:20 AM Thread Starter
Join Date: Feb 2011
Location: Oxnard CA
Posts: 18
Re: How to do the Guldstrand Mod the "hard way"

Then I cut a crossbar from 1.5x.120 square tube that I had laying around and two downtubes with 45s at the end to support it. I welded everything up and here's what I have:

I considered adding more tube to ensure things lined up, but after thinking about it I figured more tube would just be more welding and more possibility for distortion. This simple design was easy to build and the holes lined up just fine after removing the bolts (proof!)

The next step was marking where to cut.

Then I used the angle grinder and cutoff wheel to cut off the tower.

It took quite a bit of cutting and grinding to get the remnants of bracketry off the frame. Once the frame was flat and clean of the old stuff, I went to work carefully trimming the tower until the holes lined up with my jig.

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post #3 of 8 (permalink) Old Aug 4th, 11, 08:20 AM Thread Starter
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Re: How to do the Guldstrand Mod the "hard way"

I have one problem area in near the back of the tower in this photo. You can see in that area there is a gap with the frame. The crossmember has a piece that overlaps and is welded onto the frame channels. I cut so it would line up with the top of that surface. Unfortunately it didn't extend far enough so that after the trimming, the UCA tower no longer intersects it. The gap is about 1/8" and I will probably fill it with weld before tacking the tower back in for final welding.

The next job was reforming the shock mounting plate area to meet up with the trimmed UCA tower.

I started by making a pie-cut here:

Next, I inserted a long piece of 1-1/2" square tube under the shock mount hole as a lever so I could prevent it from bending down. Then I used a large adjustable wrench that I moved along the edge and little by little bent the metal downward until it matched up with the edge of the control arm tower, all the while holding the shock mount hole area up using that square tube. This worked well and I was able to keep the bend roughly at the edge of the adjustable wrench without the shock mount hole moving anywhere.

I had to also trim the edge that met with the UCA tower using a cutoff wheel. I trimmed a bit much and my pie cut was a little larger than necessary, but I think the gaps are manageable. It should work out great once it's welded up.

After finishing up all the trim & prep work, it was time to weld things up. I started by installing the jig and bolting everything in solid.

Next I tacked everything in place - four corners betwen the tower and frame and two tacks between the shock mount and tower. Then I got busy welding in approximatelly four inch sections welding the ends first, then the center. I am embarrased of the welds here: they're a bit on the cold side and my starts & stops are obvious. I haven't welded in a long time and this is the first project I've really put my new MM180 to work. Hopefully these will get the job done.

The pie cut was welded and ground flat followed by some flapper wheel to blend everything. I then cleaned up the edge with a cutoff wheel. You'd hardly know it was cut at all.

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post #4 of 8 (permalink) Old Aug 4th, 11, 08:21 AM Thread Starter
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Re: How to do the Guldstrand Mod the "hard way"

Next I bolted on the upper control arm and discovered this common area for interferance.

To gain the needed clearance, I notched and ground a small portion of the arm until it would bolt on and move through the expected range of travel. Here you can see the notched passenger arm next to the yet unmodified driver arm.

Here is the corresponding work on the driver's side:

I was very happy with the fit on everything on this side and it went much faster than the passenger side. Much less head scratching and more just working to get it done. Here it is welded up.

Both sides complete. Feels good to have that out of the way!

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post #5 of 8 (permalink) Old Aug 4th, 11, 08:21 AM Thread Starter
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Re: How to do the Guldstrand Mod the "hard way"

With the mod completed, I decided to measure my camber curve. Keep in mind my Nova’s suspension is completely stock except for the G-mod. Here are the results:

Here is how I measured:
- digital angle finder (+/-0.1deg repetability) on the brake rotor
- tape measure to nearest 1/16th from the floor to a mark on the center of the wheel bearing cap
- cycle suspension with a jack, move to a new position and measure, repeat
- 0 determined by measuring the position where the LBJ is approximately 3/8" below the average position of the front and rear bolts of the LCA frame pivots
- data includes 3 cycles completely up and down with approximately even spacing between measurements to collect a locus of points
- max and min ride are where the bumpstops just made contact with the frame
- frame supported by jackstands, suspension assembled and tight, approximately steered straight

I hope others will find this helpful. This forum was a good resource for me going into this and I wanted to return the favor.

Special thanks to Terry aka cheby2 for his writeup on this here: Guldstrand Mod , again

I'd also like thank David Pozzi for the info he's posted to his website on the G-mod: upper mount
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post #6 of 8 (permalink) Old Aug 4th, 11, 10:15 AM
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Re: How to do the Guldstrand Mod the "hard way"

Beautiful! Thank you for the detail writeup and photos. This should become a "Stickie" in the suspension catagory.

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post #7 of 8 (permalink) Old Aug 4th, 11, 01:48 PM
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Re: How to do the Guldstrand Mod the "hard way"

I agree with the sticky! thanks for the write up and the pictures. How far did you move the holes back? It looks like they are almost inline with the origanlas.

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post #8 of 8 (permalink) Old Aug 8th, 11, 01:32 PM Thread Starter
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Re: How to do the Guldstrand Mod the "hard way"

Thanks for the complements!

I bought templates from Dick Guldstrand's shop a few months ago. They do not appear to move the holes rearward at all despite what I've read on the net. One might look at the templates and assume the holes move rearward because of the way the crosshairs are oriented, but because the crosshaft on the a-arm is not level, the apparent rearward movement is really just to account for the angle of the shaft. I considered moving the holes rearward to increase static caster, but found this would cause UCA-to-frame interference on the driver's side and require some minor rework of the brakelines.
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