'59 Corvette chassis mods

Thought I'd post a couple of pics of some chassis work my son and I did on my interior guy's (Larry) 59 Corvette AME chassis. We had already built a C4 conversion for Larry for a 55 Chevy which he ended up selling because he decided he has too many projects. This project started with an AME chassis with a C5/6 front end but with bare frame rails in the rear. Larry had a few C4 rearends and decided he wanted one in his '59 without paying the $10K for the AME IRS.

The work involved putting the chassis in our frame jig at the stock 102" wheelbase. We did that by placing the chassis over the IRS we have in the jig, and locating the front spindles at that wheelbase, then building stands to hold the front end at the correct ride height. The rear ride height was kept at AME specs with some mods to the jig. Larry bought a CNC-machined batwing for the early C4 Dana 44 IRS that was narrowed about 9" from stock. It's a beautiful piece...

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We started out by narrowing the rear frame rails 4.5" and building the batwing brackets to position the center section at the correct height. Then we moved and narrowed moving/narrowing the shock crossmember.

Larry mocked up some 4" narrowed (2" per side) halfshafts so we could use them in the build. He's going to have new ones built for the final assembly.

Then we had to locate the dogbones and build the structure for them. We used a splined swaybar and fabbed some threaded plates we welded to the frame. Then we added axle bumpers, built custom shock mounts, and removed the adjustable transmission crossmember brackets and built a custom crossmember. Larry's happy as a pig in sh*t. :)

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It doesn’t look like any 59 vette chassis that I ever seen. Looks like a lot more frame than the 59 ever had. Looks like some body fitting issues in the rear trunk area. Will the corvette body fit?

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Originally Posted by Gmvette

It doesn’t look like any 59 vette chassis that I ever seen. Looks like a lot more frame than the 59 ever had. Looks like some body fitting issues in the rear trunk area. Will the corvette body fit?

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It's an AME (Art Morrison Enterprises) chassis as I said in my post, not a stock one. Yes it's a lot more frame than the 59 ever had....and a lot more engine and transmission going into it.....LS3/TKO600. Larry will be doing some body mods in the rear area to make everything fit. We consulted extensively on how to put this all together and it's not the first time someone has done a C4 rearend conversion to a C1. He should be able to fit a 305 tire under it in the rear.

You need a set of my dog bones for that thing. Or, as you may know, RideTech is building some C4 stuff now.

Who did the BatWing

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Originally Posted by NickP

Who did the BatWing

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Larry bought a set of CNC machined dogbones from Street Shop, which is who made the batwing. Don't ask me what it all cost, but I'll bet it wasn't cheap. :eek:

It would be interesting to know what the prices were, especially the dog bones. We have the plate waterjetted for them, still working on the program. They are 7075 T6. The bearings are rebuildable.

http://pic20.picturetrail.com/VOL160.../413241738.jpg

I’m assuming the dog bone are the 4 bar links? Would big rod ends and adjustable tube be better suited for dial in the suspension?

It would seem motion in more directions is necessary with a shortened swing half shaft suspension. I don’t really know but picturing the motion would be logical.

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Originally Posted by Gmvette

I’m assuming the dog bone are the 4 bar links?

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Yes

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Would big rod ends and adjustable tube be better suited for dial in the suspension?

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If you wanted to rattle your teeth out.:p There are companies that sell them and reports are they're pretty harsh for street use and wear out quickly. They would be great for autocross racing. I'm using urethane in mine and I don't remember what Larry's had for bearings/bushings. I don't know what you could "tune" by having adjustable dogbones except for compensating for the pinion angle, which is fixed on these rearends. We install a bracket from the pinion snout to the shock crossmember and you can see the urethane bushing boss tube in the pictures. You would have to change the location of the front dogbone attach points to affect anti-squat and camber can't be adjusted with the dogbones. So what "tuning" would you do?

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It would seem motion in more directions is necessary with a shortened swing half shaft suspension. I don’t really know but picturing the motion would be logical.

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I don't know what you mean by "more directions". The motion is still the same but some of the angles change slightly. Keep in mind that these suspensions typically travel 2" up and down total range of motion so angles are not severe. The halfshafts are shortened 2" out of 18.125" stock length which is a little over 10%. Lots of cars have been set up with narrowed C4 suspensions, some up to 3" per side shorter. Mine is narrowed 1.5" per side which puts the axle at almost stock tri5 60" width.

What is the big benefit of a narrow axel over a wide axel, especially on an IRS? Seems backwards to me. Something to consider, with your single shear dog-bone mounts, it would be a great application in which to use spherical bearings on., which would eliminate the twisting forces. A little noise is just part of the mechanical symphony.

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Originally Posted by 55 Rescue Dog

What is the big benefit of a narrow axel over a wide axel, especially on an IRS? Seems backwards to me. Something to consider, with your single shear dog-bone mounts, it would be a great application in which to use spherical bearings on., which would eliminate the twisting forces. A little noise is just part of the mechanical symphony.

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This is exactly what I was inquiring about but c-nut discounts that. You (55 Rescue Dog) seems to understand my concern. “More directions” as in arc travel not linear straight line. The smaller the arc radius the more inward and outward displacement. I just see a lot more than 2” spindle movement up and down suspension travel on an arc path centered on the inner u joints. Spirited driving will see a lot more. So I don’t buy 2” travel. Pot holes are more not to say inclines and bumps.

The purpose of a 4 link is to control the up down movement so it is more linear rather than arc. True this is more of a concern with a sprung differential. Thus the position of the pivot and link length will have optimum functional positions and lengths. This is what is implied by “tuning” regardless if a fixed or sprung differential.

Like clockwork, every time narrowing a C4 IRS is mentioned on any thread RD has to jump in with his incessant "I don't see how/why blah, blah..." BS. I've explained all of this extensively, at least two or three times if not more, so go dig up the info or grab a pencil and paper and figure it out for yourselves with real numbers like I did. I'm tired of having to do your homework for you and you just don't learn.

There are no significant twisting forces on the dogbones as I've proven in the past. As for travel, go and look at the travel of a typical coilover shock and maybe you'll start to understand what's going on in the real world. My upper axle bumpers sit 2" above the pads on the knuckles. Yeah, I think that's pretty close to 2" of upward travel. Even if it was slightly more, the geometry changes aren't significant.

Then when you can explain in detail how narrowing a C4 IRS 3-4" negatively affects anything, and by how much, please post your results. I've calculated and posted the differences in camber gain between a stock width C4 rear and a 3" narrowed one over the range of travel and I showed that it isn't significant. Changing the pivot points affects geometry more than narrowing it. GM did that in 1988.

When you study and understand what a C4 IRS does maybe it will start to make some sense. You talk in generalities and don't understand the details. I still want to know how you "tune" a C4 suspension with the fixed dogbone end locations. Adding adjustable rod ends doesn't change those pivot locations.

Now I wonder how AME narrows a C5/6 front end 5-6" without causing something to break and the car to wreck. And how can their 55.5" wide IRS possibly work being that narrow? Can either or you explain that? :-D

Narrowing a C4 IRS allows you to run a wider tire under the car with a deeper (less positive offset) wheel and it makes changing the tires easier. It's that simple, and there are minimal if any negative effects. How many times have I explained this now? :eek:

The wheelwell lips on a C1 are 68" wide inside, which is over 3" narrower than a tri5.

So, I guess AME doesn't know what they are doing either by offering 4 different widths on their IRS.

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Originally Posted by NickP

So, I guess AME doesn't know what they are doing either by offering 4 different widths on their IRS.

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My point exactly. I'm still waiting for either of these guys to post their detailed analysis of what happens to a C4 rear when you narrow it. I'm guessing I might be waiting for a long time. :D

I recall that I worked up the actual movement in all directions for this very same discussion b4. As memory serves me the distance in actual motion difference was less than .04" from stock width versus your Nomad unit. search might reveal those AutoCAD drawings.

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Originally Posted by NickP

I recall that I worked up the actual movement in all directions for this very same discussion b4. As memory serves me the distance in actual motion difference was less than .04" from stock width versus your Nomad unit. search might reveal those AutoCAD drawings.

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I used CAD to lay it all out and calculated the change in camber in 2" of travel for an early C4. late C4, and my narrowed late C4 I'm not going to re-post my results until the peanut gallery posts their results, or admits they have no clue which is probably the case. :D

I predicted before I started this thread that RD would spew more of his BS about the narrowed rearend. True to form, he didn't let me down. :p

noun: peanut gallery;

• the top gallery in a theater where the cheaper seats are located.
  
  • a group of people who criticize someone, often by focusing on insignificant details.
  
  
  

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Narrowing a C4 IRS allows you to run a wider tire under the car with a deeper (less positive offset) wheel and it makes changing the tires easier. It's that simple.

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Yup. My stock C4 width rear means a not-very-deep dish wheel and I have to drop the bottom shock mount to drop the rear halfshaft low enough to get the wheel to clear the fender. 57 rear fenders are not that "high" to start with.

That's a nice C1 AME frame mod there Laszlo. Good work. That corvette will drive like a slotcar when it's done. Woot!

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Originally Posted by WagonCrazy

Yup. My stock C4 width rear means a not-very-deep dish wheel and I have to drop the bottom shock mount to drop the rear halfshaft low enough to get the wheel to clear the fender. 57 rear fenders are not that "high" to start with.

That's a nice C1 AME frame mod there Laszlo. Good work. That corvette will drive like a slotcar when it's done. Woot!

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Thanks Paul. :cool: The limiter for tire width is the distance between the dogbones and the fenderwell lip on these C4 chassis. The only way to increase that is to move the dogbones inboard, which requires narrowing the frame. The distance from the wheel mounting surface to the dogbones stays the same, but you gain room from the wheel mounting surface to the fenderwell lip. That means a deeper (less positive offset) wheel is needed. Some people seem to have a hard time grasping that concept.

This chassis was a real challenge to design due to all the constraints imposed by the body, suspension, frame, etc. We ended up using the same Strange coilover shocks on the rear as AME uses in the front and they worked out perfect. I wanted to use slightly longer ones, but we had no room. Pretty much every bracket is a custom design and was cut by hand. The shock mount tube is 1.75" x .188" Chromoly that Larry wanted for that purpose. I set up the lower coilover mounts to achieve the correct ride height shock length.

As I may have mentioned before, Larry and I are trading labor for my interior. He wasn't sure if the time I had in his 55 frame would cover all the labor on my interior but in doing this job for him he said he'll do whatever I want on my interior until it's the way I want it.....no charge. He's very meticulous and I need to get him going on my stuff soon.:eek:

The chassis you modified looks great, and will probably work fine on a lightweight C1 on a smooth road, but I am thinking as far as track width goes, sometimes maybe a narrower tire might work better? After all, anytime you try and put a wider tire inside the bodywork of any car you are narrowing the track width, which I would visualize that it messes with the roll centers, which don't get discussed much. And I don't have a clue as to how all of the factors that work into it along the front/rear roll-axis, roll-stifness, etc.??? Drawing lines on paper will get you close, but actually dynamic testing of any tire/suspension setup is just important. An IRS makes it even more complicated. Testing would explain it better instead of just coloring inside the lines. Big wheels/tires look the best, but
simply just stand with your big feet together, and lean.
Here is a great technical paper by Michelin that will tell you more than you ever want to know about tire grip, and all the variables. I was surprised at a lot of things about tires I still don't know.

https://www.paradigmshiftracing.com/...p-michelin.pdf

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he said he'll do whatever I want on my interior until it's the way I want it.....no charge.

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That is a smokin' deal Laszlo. Hurry up and get him started before he finds a reason he can't get to yours...you shoppin' for cow hides yet?