Grafting a C5 rear suspension on C3

phantomjock

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Nice - but just like using an XKE rear end - mixing pedegree! But what can I say - I'm mounting 4x48 Webbers on a SBC! Downdraft - not sidedraft, like the GS! BTW - didn't they put a circle around it - to cleary identify the Problem? (FORD)

Anyhow -I spent a great afternoon at the FactoryFive shops, showroom etc. Great products, fantastic work environment, and each employee focused on getting their customer/guest the info needed. Powdercoating is done off site - but all the fiberglassing, welding and basic assembly on site. Did a full tour of the factory and a heap of pics if there is interst - I'll hang on my pics page.

I spent a lot of time evaluating and "shooting" the rear end on the GTR - and their frame that has a drop in of the wishbones and toe control from the C5 - wich is really germaine to this thread. I'll post when "developed."

For me @ 200# and 6'3" the Daytona Type 65 - just fits - but surprisingly the Pontiac Solstice fits better, the Hot Rod - ok but not my style, and the roadster MK4 - too short in the foot box for long term use. The GTR - while sweet, entry/exit tougher still - the overhead cage a bit of effort - halo and all.
But, I have some nice AIRBOX pics that will be will be forthcoming along with the rear IRS showingthe C5 bits installed.

Cheers - Jim
 

Twin_Turbo

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What kind of downdraft intake? I have a nos SBC "ultra" intake somewhere, set up for 48 IDAs.
 

Ralphy

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The upper link is only bent for frame clearance. The coilover only needs to be to the rear to avoid twisting the LCA. And what if you were to add an upper watt's link like this and move the coilovers forward?
http://s350.photobucket.com/albums/q401/acmjg/?action=view&current=MOV04917.mp4

Also to stabilize the C3 carrier add links like this fore and aft with L/R heims.
http://www.todaysauto.net/musclecars/badboy/splash-showtruck(19).JPG

how about this??? It's only $8000 and it sure looks cool with the brake rotors inboard.... :D

214ec9aa6ae7245.jpg

How do you adjust the camber (without removing bolts and stuff) on that setup?

The article quoted is in the Jan 2012 issue of Super Chevy. If you look at the article or the Heidt's add on page 59, you will see there is another link that runs from the outboard end of the lower control arm forward to a chassis pick-up point. This arm absorbs the forward and rearward thrust to prevent the lower control arm from flexing fore/aft. The lower control arm also controls the toe (note no toe link). The only thing that makes me nervous is the single upper link with no forward link to prevent forward or aft movement of the top of the spindle. With enough acceleration or braking force, you might twist the lower control arm enough to get some movement. I still prefer two forward links to take the driving and braking forces (with adjustable instant center for anti-squat/anti-dive control), an upper and lower link above and below the axle with moment center height and camber adjustment, and a rear toe link. This configuration, similar to the old Can-Am and original GT-40 cars, when run with newer, stronger CV joints and axles and ZR1/SKF wheel bearings should perform well. Another very interesting article you might want to look at is on page 68 on the Nov 2011 issue of Camaro Performers. That article shows installation of a 9-inch Ford-based IRS differential set up with CV joint axles for the new Camaro. It would be very easy (LOL) to adapt that differential housing to an early Corvette by welding different mounting brackets and provisions for the upper and lower links. My $.02 worth.

Pappy
 
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mfain

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Ralphy,

That upper Watts link is interesting. It makes the upper end of the spindle travel in a pure vertical line while the lower forward link swings the bottom of the spindle in an arc -- this would slightly change the caster with suspension travel, but that should not be too significant on the rear suspension, unless you end up with dead zero caster, in which you might pick up a "shimmy". Using only an upper forward link (instead of the Watts link) would be similar to using a panhard bar instead of a Watts link to center a straight axle. I will have to give some thought as to what the Watts link does to the instant center as the spindle travels up and down -- might be some affect on anti-dive/anti-squat (good or bad??). In any case, I think an upper forward link is required to stop any movement of the top of the spindle fore or aft during hard acceleration or heavy braking. By the way, the lower forward link in your posted video is very similar to the one on the Heidt's IRS. The upper Heidt's link is indead bent for clearance -- not too good of an idea since the link is in compression and the bend might allow some flexing. I'm still dreaming of cornering forces in excess of 1.5 lateral g with big, wide, sticky tires and 850 horsepower trying to twist the suspension into knots -- I tend to be on the side of "overkill". LOL

Cheers,
 

phantomjock

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The Jag setup is an interesting one and I spent a few hours looking at a site pretty much devoted to them. The "dogbone" instead of "wishbones" seems so, well "Lucas-like," but simple in approach. The inboard brakes raise a lot of discussion on the sites where guys are converting their 2nd gen suspensions. Potential difficulty to access to change pads, unsprung weight, cooling, etc. And - hey- if it is going to cut up the interior anyway -- WHY NOT?

TT - here is a shot shamelessly swiped from Jim Ingleese's site:
thum_12694ecb7590cd859.jpg
My rig is similar - carb bodies will be gloss black when completed, 1/2 way through polishing the aluminum intake manifold. When assembled and on the SBC - I'll take some assembled pics.
Jim and I have been wondering the make of my manifold - it may be a "Fast Freddy" from the west coast. Similar style to the one above - but with "cooling fins" groved into the topside between the IRs and a large rectangle and "W" in the casting too. It has the below deck vacuum set up - but I won't use it much with hydroboost and a crank trigger Electromotive setup. I was told it was manufactured by Weber - but no indication (pn/sn/etc) on the manifold casting.

That wasn't tooo far astray - even used "IRs" when talking Carbs(albeit, independent runners!)

Cheers - Jim
 

Ralphy

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Pappy,
If you like overkill, you should love this build. Able to withstand 1,400 HP they say. LCA's are 1 5/8", uppers are 1 1/4". If you select the, I think 600HP half shafts, do you need that heavy of control arm's? LOL!


http://www.roadstershop.com/images/documents/irs_details.pdf

Also the previous video shows with the guy using the Jag dog bone. Again I would toss it for an aftermarket wishbone and remove the forward link. Then add the watt's. The watt's was added to avoid wheel hop. Believe it or not, there are guys running with only the dog bone! Ouch!
 
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phantomjock

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IRS Characteristics Chart

In my crawling of the web - came across this chart.
Ought to raise some intersting discussion opportunities:
12694ecbdd56a694f.jpg

Ralphy - this will look a little familiar ;)
Cheers - Jim
 
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phantomjock

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Continuing the C5/6 IRS graft on a C3 question - just a detail question someone might have the answer close at hand...

thum_12694ef8b21405684.jpg

Would save a bit of work if that is the case. Would need an adapter to match the 4 hole mount of the C3 to the 3 holes of the C5/6, but that should be straight forward - No?

Cheers - Jim
 

MYBAD79

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how about cutting the C5 half shaft and "adapting" it to the C3 shaft ? maybe a telescopic splined connection so that you have some tolerance on the new half shaft length ??

why would you want to adapt it to the 4 hole mount ? if i had all these parts I'd try to eliminate the old trailing arm alltogether.
 

BBShark

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Continuing the C5/6 IRS graft on a C3 question - just a detail question someone might have the answer close at hand...

thum_12694ef8b21405684.jpg

Would save a bit of work if that is the case. Would need an adapter to match the 4 hole mount of the C3 to the 3 holes of the C5/6, but that should be straight forward - No?

Cheers - Jim

Not sure I'm following this but, if you wanted to use a C3 style ujoint shaft, you could use a C4 stub axle and bearing hub.
 

phantomjock

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Hey Guys - sorry for not being so clear - Obscurring the facts - another service I provide for free!

It is a challenge of minimizing "sunk costs" vs. new totally new start.

I have already had the TAs redone - did the Johnny Joints, then sent off to get new rear bearings, rotors and Areospace Calipers added.
Cha-Ching with Bling!



thum_12694eac8a585e088.jpg

Then, I had the Diff gone over and 4.11 gears added (Tom's) - to mate with the 200-4R up front.
CHA-CHING!

Next, while on the Giovanni, knew I'd need slip yoke half shafts, so I have a pair of those too.
Cha-Ching--Less Bling - but pretty cool.

Naturally they mount to the standard Speicher 1350 mounts on the spindle and diff... (I was thinking I could cobble a few pieces together - but a clean sheet of paper is called for. BUGGER!)

So, It may look like I get to do the FAB-four. Fabricate:
1) New spindle uprights,
2) Upper and lower Wishbones,
3) Sub-frame,
4) ETC!

Ohh, might add - Santa left a MIG welder - so now I have fewer excuses not to build something!

My plan (today) is to model my IRS after the C5/6, use my also cha-ching Dual Mount Fiberglass spring - relocated like on C5/6 (forward a bit), keep the sunk costs and reincorporate as much as I can.

I can see it would be easier to start a C5/6 graft with no "investments" other than a frame and go roto-to rotor with C5/6 components.
Hind Sight is 20/20.

Hope that is clearer than before - this is all evolving and thanks for the help!

Cheers - Jim
 
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MYBAD79

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do you already have the C5 spindles and upper and lower A-arms? might be less pain to use the C5 stuff and forget about the C3 spindles,bearings..... changing your mind half way into a project is expensive.... one reason why I decided to say "F it" and now I'm going with a stock setup .... I want to drive this car in 2012, it's been sitting all year 2011

custom half shafts to adapt from C3 to C5 is probably your best and easiest way....
 

phantomjock

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Karsten -
I don't know if its fortunate - or unfortunate, but I have no c5/6 parts! At least there is still some space in the garage because of that.

I was engaging the idea to try and see if there would be a middle path through this muddle I'm in.

And tell me about it - I think I last drove the 78 when I moved it from MA (storage) to FL in 2005 or 6! Then in 09 - I started this mod effort. My return to AD put that on the back burner, and though fortunate to have a small bit of disposable income -- its not enough to toss the investments in bits I have now on hand.

I'm thinking my best compromise will be to "replicate" the key elements of a C5/6, build a sub-frame to hold the Diff, wishbones/H-bones, appropriately placed dual mount leaf, upright/hub carrier, bellcranks for shocks inboard, and a toe control bar or 2.

Now to do the design work, get the Roll centers/rear bump steer figured out along with some adequate camber control, minimze jacking and transients, OH-LA-LA, up hill all the way!

It looks like I won't be doing a "Graft"of a C5/6 to a C3 - but a "CLONE."

But on a solid note -- this has got me back in the books and where I wanted my degree to take me when I started - but that was long before the shiney glitter of jets...

Hope everyone's new year looks as bright and hopeful as mine! Ohh - wait a minute - let me take off these rose colored glasses ;)

Cheers - Jim
 

JeffP1167

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Are you going to sell any c5 suspension stuff well if you have any? I want to do a c4 conversion on my 82 but if I can find c5 stuff may as well go for that.
 

phantomjock

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JeffP1167 -

Sorry I have no C5/6 suspension bits - there are always some on eBay and Craigslist - from my experience. There is one set that is Rotor to Rotor for less than a grand on eBay -- oh yeah - less than 3000 miles on it too. (no diff) When you add a Diff to the project the price usually hangs at $1500-$2000.

I'll share (downloads section) anything that makes sense when I get it done and driven, But at this point it will be a DIY interpertation of a C5/6 IRS on a C3.

Cheers - Jim
BTW - I do have some stuff in the for sale section - if interested!
 

JeffP1167

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JeffP1167 -

Sorry I have no C5/6 suspension bits - there are always some on eBay and Craigslist - from my experience. There is one set that is Rotor to Rotor for less than a grand on eBay -- oh yeah - less than 3000 miles on it too. (no diff) When you add a Diff to the project the price usually hangs at $1500-$2000.

I'll share (downloads section) anything that makes sense when I get it done and driven, But at this point it will be a DIY interpertation of a C5/6 IRS on a C3.

Cheers - Jim
BTW - I do have some stuff in the for sale section - if interested!

so why not do a c4 conversion? either way that is light years better then c3, make a jig and graft it all in.
 

phantomjock

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JeffP1167
That could be an option - and clearly others have followed a similar path.
I was (and still am) fascinated at the reasonable prices you can find Rotor-to-Rotor C5 setups. I am willing to bet the C5 IRS is again another order of magnitude improvement even over the C4-- and light years ahead of the C3.

I've continued my searching and there is an outfit in NC (21st Century Street Machine - just outside of Charlotte) that builds a Subframe that could be "reverse engineered" to accomplish the grafting:

thum_12694eff04f6c31b8.jpg

Its not too far off the ideas I originally sketched out in Post #1.

Now, I have some designing to do. Model a similar approach, subframe and IRS using my existing C3 bits as I've described previously.
It will mean:
1. A new Hub/upright -- Not as "klunky" as the Greenwood Box--with fittments for toe control & torsion bar
2. Upper Wishbone, maybe lower H-Bone,
3. Pushrod & Belcrand for dampers,
4. Double mount composite leaf spring,
5. Remove and replace Diff Carrier,
6. And, the entire space frame mounting structure.
7. Build, assemble, install, and move on to the rest of the car!​

I was planning on using Rhino - but may opt to work in SolidWorks - there are some really complete Tutorials available from SAE.

Whew - thats no short list -- I'd better get cracking.
Oh - BTW - I'll be checking all the IC/RC and CG during the design to try and make it as close to an improvement that at least "works," and is a goood match for the front end mods [mono leaf new lowers and uppers, rack and pinion] and wide tires all around.

I can't recall the author - nor find the exact quote - but it was something along the lines;
Its easier to make chassis (suspension) improvements than to start from scratch and hope to design the ultimate solution...

FOUND IT-- It's Paul Van Valkenburgh - Race Car Engineering & Mechanics:
The best be is to modify what exists, or to build and test, rather than try to design the ultimate suspension from theory.

I'll have to print and paste to my computer screen!


Cheers - Jim
 
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