AlkyIROC

Setup, yes. Work, no. It's not going to win any car shows. It's functional, not pretty. The trimming around the roll cage tubes isn't precise. The 3 pieces across the back, the center piece is slightly shorter (front to rear) than the side pieces.

This weekend I managed to redo the passenger side floor. I cut out the old recessed area that would be under the passenger seat and the box I created to go over the ladder bar front mount. I welded in some new sheet metal to fill in the hole. I've been considering doing the driver side but that would mean refabricating new seat mounts to the SFC and putting the seat directly on the floor since the floor would be then be higher. The shape of the floor isn't the same on the driver's side as it is on the passenger side so I may just leave it. While part of the floor was out, I cut out the old ladder bar front crossmember. That was heavy. At the time when I put it in, I used 2 x 4 x 1/4" steel. Way too thick for what was required but it was all I had at the time. 0.083" or 0.125" material would have been fine.

I also secured the wiring going to the back. I installed both tires to check fitment. It's weird. The passenger side fender opening isn't the same as the driver's side. I needed to trim more off the back side of the opening than I did on the driver's side. I'm trying to allow 2" of clearance to compensate for any tire growth.

I picked up a 4" mandrel bent U-pipe today to make exhaust turnouts. Cutting it in half then trimming the radius so the exhaust comes out past the rockers at about 45*. I now have the exhaust exiting out from under the car instead of blowing back onto the tires.

I also picked up some 3/16" Lexan to redo the windshield although I never got around to cutting it yet.

I removed the driveshaft loop because I changed the floor where it attaches. I need to fabricate a mount between the SFC to install a new driveshaft loop to.

Other than that, just a general cleanup of the garage. Picked up all the pieces of cardboard and sheet metal that were trimmed and cut off. Swept up a huge pile of metal filings from all the grinding. I ran out of MIG gas again and had to go get the bottle filled/swapped.

AlkyIROC

More pics.

The windshield is out. Here's a bunch of pics looking in through the windshield.

AlkyIROC

Pics looking in through the door and a shot of what the passenger side floor now looks like.

AlkyIROC

Here's what the exhaust turnouts now look like. 4" outlets coming out just below the rockers. The passenger side looks the same but there's isn't enough room for me to get a good picture of the side.

AlkyIROC

One last picture at this time showing how the tire sits inside the fender. I'm hoping this will be the proper ride height. Until I get the car back on 4 wheels, I can only guess with measurements. Those are 15" wide rims with 5.5" backspacing. I also ordered my new tires today. MT 32 x 14S (stiff sidewall). I ordered them to come in on a regular stock order. I'm guessing I won't see them until the end of February but I'm in no rush.

cp87GTA

Stephen, you are really going to like your 4 link car once you get it set up. All I ever had was a leaf sprung car before my GTA. When I built my Grand Am last winter, I was kind of scared to run it the first time. All my buddies had me believing it was going to stand up bad cause it is so short wheelbase. Not true, that car handles like a dream. It runs the same et durring the summer as my T/As best time, with 800 rpm less. I'm running a 14.5 32 hoosier on it, and it only has about 1/2 air under the front wheels. First move is forward. Had very few red lights last year, because it rolls through instead of picking out. I'm just getting started on my sons 96 bird. Going to back half it this winter. I had mine tuned with the 3 adjustment on the bars. Then went to the shocks.

AlkyIROC

Where were your bars positioned? What was your IC?

AlkyIROC

I picked up Performance Trends 4-link calculator a little while ago. The other choice for 4-link software is 4-link wizard. PT is nicer because you can change the ride height (adjusting the shock mounts) and all the bar mount points can either stay the same or move with the height change.

I did a rough measurement based on the original ride height before the project started to where the car sits now on the jack stands to calculate the height of all the bar holes. Once all the mount points are plotted into the software, all the instant center points are shown. The software also gives a recommendation as to where the IC should be based on car data you input.

I've readjusted the bars to give a 44.1" IC length and 3.7" off the ground with a 45.9" anti-squat. This is only a recommended starting point. Depending on how the car reacts at the track, the bars can be easily adjusted to change the IC length and height. Also once the car is back on the ground, measurements will be taken again to see how far off I was.

From all the adjusting holes, the shortest IC point I have is 25.6" forward of the diff centerline and 10" off the ground. Farthest forward is an unrealistic 507" forward and 88" below the ground. I still have a few hundred more practical choices for an IC.

I've come up with a new idea on how to reinstall the driveshaft loop. Instead of making long mounts to reach out to the SFC, simple, short, 12" long tubes will be welded to my fabricated tranny crossmember and the driveshaft loop will be welded to those tubes. Simple and clean and it cuts down on the amount of metal required. I just need some more metal to make it.

soulefood

stephen, do you recommend that i go with a pre-fabbed 4 link frame like ones found in jegs, that already have the bar ends and links, also with a coil over kit? also i measured my rear end and from the outside 4-link bracket across the pumpkin over to the other outside 4 link bracket measured 24 inches...? the frames offered in jegs are only 26 and 28 i do believe. hmm i feel like this is going to be a major headache, along with routing the piping for my turbos
----------
i will take some pics of it tonight and post them... just found out also that the rims i aquired with the rear end aren't the right bolt pattern.. so now i have to take the rear end to a machine shop and have the old studs cut off and new holes drilled and studs pressed in.. ugh

AlkyIROC

The prefab kits are the best way to go. There's still a lot of work involved doing the backhalf project but a kit takes a lot of the guesswork out of it.

83 Crossfire TA

iTrader: (2)

Huh… based on what I’m seeing there and previous pics of the exhaust, won’t that put the mufflers on the ground and the bottom of that outlet like 1” off the ground?

AlkyIROC

Until the car is sitting on the ground I don't know. I can always adjust the ride height with the coil overs to bring the rocker panel back up to where it was before the project. The mufflers originally were 4-5" off the ground. I don't have my spec sheet handy but I believe the bottom of the rocker panel was 6-1/2" off the ground before I started cutting.

crazyboutracing

Stephen, what was the amp of your 110V welder? I'm backhalving a Malibu wagon, and I figured I'd need a 220V like a 180 amp or so. I got a 130 amp 110v Lincoln welder available to use.

AlkyIROC

30-120 amps

Duty cycle
80 amps at 40%
120 amps at 18%

I used .025" wire

Correction. I used .023" wire. The smaller wire melts easier with a lower amp welder. If I had a 220v at home, it's be using .030" or .035" wire.

AlkyIROC

New MT are installed (no pics yet). The ride height was about an inch lower than originally. I had to move the shocks up 2" on the axle brackets to get the ride height back up close to where it originally was.

Now that the car is back on 4 wheels, I can see I need to recalculate IC points for the 4-link. The axle brackets sit lower than anticipated. Actually they're about 3" lower than anticipated. Bottom hole on the chassis bracket is 7". Bottom hole on the axle bracket is 8-5/8".

I'm going to get rid of the diagonal link and install a wishbone as soon as it arrives.

Only 3 months until the first points race.

AlkyIROC

I got some new pics!

First 2 are looking in through the back window. There a bit of glare off the Lexan but you at least see the tin work.

The third picture has the camera almost sitting on the floor at the rear looking forward. There's a flash glare off the crossmember that I can't edit out.

AlkyIROC

OK, Now this doesn't look great but should still work. I only took pictures of the passenger side tire because the driver's side would have been in shadow. The driver side wheel opening looks much better than the passenger side. The factory body is not symmetrical from side to side.

Although the opening looks tight, it's an illusion. The tire is actually inside the rear part of the opening. The ground effects make it look like the tire is closer to the fender than it really is. There's actually 1 to 1-1/2" between the tire and the closest piece of fender. Behind the ground effects, the metal part of the fender has been trimmed back. A wheel opening that's been properly opened up would look better. That requires more sheet metal work than I want to tackle.

The last picture is just another shot of the passenger floor.

Sonix

iTrader: (1)

Hey right on, thanks for those pics.
Looking from underneath all I can think of is ; "it ain't pretty but it works"

I'm going to have to be a spectator at one of the races you're in. I'll finally be out of school with some free time and money.

AlkyIROC

"It ain't pretty but it works"

I'm not sure if I mentioned that in this thread or not. Go find a home built custom car like an old 51 Merc or something like that and take a look under it. Normally the body and interior will look real pretty but the underside says it's all backyard homebuilt stuff. Not everything you see is show car quality. Most of what you see on race cars is only cosmetic.

BlueBeast

Looking good, you have done a lot of work to this thing. Friend of mine is in the same process. Keep the pics coming.

AlkyIROC

None of these pictures in this thread are on my web pages yet I guess I'm just lazy. As I mentioned on my web page, I just finished doing a backyard wheel alignment. I needed to reset the toe. Old school method of wrapping a string all the way around the car then adjusting each front wheel along the string. Not sure what the toe actually is but it's close enough for me to get it into an alignment shop without scuffing the front tires off.

Here's the kicker. The outside edge of the front tires is exactly the same width as the outside edge of the rear tires. I didn't plan it that way but it's so close you'd think it was.

To get the rear to that width I measured out the narrowed diff to be 45" from axle flange to axle flange. The housing width is 40". From rough measurements that's just what looked like would work the best when I first started. It was a ballpark guess. The rims are 15" wide with 5.5" of backspace. There's enough room to put 6.5" backspace rims on if I wanted to. It would stuff the tires under the fenders another inch. Tires are MT 32 x 14S (Stiff sidewalls). Pinion was centered in the car and the diff is centered to the chassis. The fender openings are not the same from side to side which you can't see with much smaller tires. There's a lot more room between the top of the tire and the fender on the passenger side than there is on the drivers side. The front to back opening is also different from side to side. Mention that next time someone says that it looks like their diff isn't centered under the car.

AlkyIROC

OK, just went out and took a few more pictures to see things from different angles. The car is back in the garage and out of the direct sun.

First pic is looking at the driver side tire. Best angle I can get right now. See the second pic for how much junk is in my garage.

Second pic is from a low angle at the rear. My garage is much higher than the alley and I'm crouched down slightly. Even though there's a slope to get into the alley, my exhaust doesn't scrape but it's very close.

Third pic shows the opening behind the passenger tire. I may trim it back a little more and cut down or eliminate the ground effects mount bolt. That may cause a problem more than anything else with tire growth.

I now have the ride height adjusted about to where I started from. The distance from the floor to the bottom of the ground effects directly under the rear corner of the door is just under 10".

AlkyIROC

Just a few more pics.

First and second show how much wheel opening is at the top. Not sure how good this angle will show it but it's the best I can do.

Third picture shows how much clearance there is on the inside rear of the passenger tire

AlkyIROC

A pic showing ground clearance. The camera is sitting right on the floor. 4" exhaust outlets. On the right side of the picture you can see my SFC welded to the underside of 4-link crossmember.

Last pic just showing the rear. You can see the pipe coming out the back for a future parachute mount. I don't need it yet but during construction, it didn't take much to add it in. The battery master switch mounted to the right of the license plate. Skull and crossbones license plate to match the car theme. Boost posts to easily boost the battery without having to take the deck lid and battery box top off. The factory lettering on the left side still says "5.7L Tuned Port Injection". On the underside of the bumper cover you can just barely see the air ports when I ran air bags in the springs years ago. I just never took them out of the cover.

AlkyIROC

I had the car out today and forgot to take my camera. I got onto an alignment rack which was interesting with my mufflers. Last year when I got my car aligned, it had open headers. The back end is square. Not bad for a measuring tape and plumb bob. The back wheels however are slightly toe out. When I welded the back brace onto the housing it must have pulled the housing back. I'll run it this year to see if there are any issues that need to be addressed. If it's bad enough, I'll have to pull the housing and put it in a press. With my luck, I'll break an axle on the first day out.

I also got across a scale. Front end weight is still the same as last year with 1850 pounds on the front tires. The rear actually lost some weight after doing the back half which really surprised me. Last year it came out to 1234 pounds but I can't remember if that was before or after I added the mufflers. This year the weight on the rear tires is 1212 giving a total race weight with driver, fuel etc of 3062 pounds. Took off around 23 pounds over the winter. Most of that was probably in the narrowed diff. Could have shaved off a little more if I used aluminum instead of sheet metal for the back half tin work. Don't want the rear to be too light though.

It was a 60/40 nose heavy car last year and now the nose weight is just under 61/39 ratio. 50/50 is the goal to reach. Maybe I'll need to put a wing on the back to provide some downforce at 140 mph.

IrocSS85

damn dude, very cool project. Ive always liked your race car. prolly the exact same road this firebird Im currently working on (where you sendt me th elink to this post from) is heading. for now the mini tub will have towork. but, I have an 86 Iroc that this is excatly what I want to do with. good luck, and hope it all works out for you. Ive heaard that even when welding axle tubes, alot of care has to be taken to keep the tubes streaight in the housing.

also, very interesteing info on teh welder you are using. I have a sears (lincoln) welder thats sounds like the same one. but I think i have .035 wire in there. never though of thinner wire meiting easier, allowing thicker metal to be welded. Ive pretty much only iused it for sheetmetal and exh. and stuff. I'll have to try some thinner wire and weld some thicker steel. Id do my own roll cage if this welder will work.

at what point do they make it nec. to have the seat bolted to the SFC's?

all in all, excellent job, and you give me hope that maybe one day I'll do my own porject like this.

chris

AlkyIROC

When it's not a factory seat attached to factory mounts.. The original mount studs are cut off the floor. I'm using some 4" aluminum Z brackets to mount the seat to the floor. The seat is sitting about 6" back from the original location. Just bolting the seat through the floor isn't acceptable even with large fender washers. It must be attached to the frame or crossmember. The easiest way to make my seat secure was to weld angle iron extensions off the SFC which runs directly under the seat. The seat mounts are then bolted through the angle iron making it secure and part of the frame. If you can attach a seat to the factory mount points, that will be good enough.

I've probably already mentioned it in this thread but doing a back half project is a big project. I wouldn't want to do it again. I've heard estimates that if you take your car into a chassis shop to have it done, expect to pay at least $10,000.

Although it's not a perfect job, it still came out nicely.

85z28guy

Looks like a great project man Have you tried it out yet?

AlkyIROC

Whoops. Sorry for the late reply. I've had it out a few times this year. As of today, I now have roughly 50 passes down the track this year. I was having traction problems this year with poor 60' times. The problem wasn't completely a 4-link problem. I ended up replacing my torque converter and yanking my tranny out twice to fix it. The season is almost over and I want to try one more IC position to see if the 60' times will drop some more. So far I've been able to set a new personal best ET and MPH and almost equaled my best 60' time. No other changes to the car since last year except the back half project and some tuning. I'm still waiting for an adjustable rear anti roll bar to arrive. I need to get it installed before the next race. The 4-link suspension really lets the body twist on launches. I need to square everything up so I don't try to take out the christmas tree when in the left lane.

You can see pictures of the car going down the track in the racing forum under a link I posted about new pictures. As low as the exhaust sits, ground clearance isn't an issue when going down the track. The big tires do look good. Much better than the smaller tires sticking farther out of the fenders.

BT283

iTrader: (3)

How much does your car weigh now compared to stock suspension.

AlkyIROC

Stock suspension, no idea. I had ladder bars before the back half. The ladder bar front crossmember I was using was big and heavy. After the back half project, I was able to shave 20 pounds off the back of the car even with all the extra roll cage tubing that was added. Last year the race weight was 3085 pounds. In the spring when I weighed the car again, it was 3062 pounds. The front weight stayed the same so it all came off the back.

Over the race season, small things change so the race weight isn't always 100%. That 20 pounds may return after the rear anti sway bar is installed.

I plan on installing an aluminum center section and aluminum spool into the diff over the winter. That should take another 20 pounds off.

PedalToMetal

Cripes that looks bad-***!

Tubbythumper

Great thread. I'm putting together an 86 with a BB. My intention is to back half. Your info is priceless. Glad I found this forum.

AlkyIROC

Don't expect miracles but I'll answer any questions that I can.

After going out for some track time last night I can add that a rear anti roll bar is a necessity. It made launches very straight and eliminated all body roll.

CG_1985_Z28

looks good

AlkyIROC

This picture is also in another thread but here's what the diff looks like now with an anti roll bar installed. Yes it needs a bunch of paint but the car also isn't driven in the rain. The anti roll bar made a huge difference in how the car launches. You can see how much room I have between the tires and the frame rails.

sradams21

iTrader: (1)

for those of us who don't wanna do all the math part of the fabrication S&W Racecars has a backhalf kit with the rails and crossmembers already welded up, and you get your choice on 4-link or ladder bars

OLDMAN57

Nice job how long did it take?


Don

AlkyIROC

From when I made the first cut to when the last piece of tin was put in took roughly 3 weeks. The majority of it was done in less than 2 weeks. That's not counting the time it took me to narrow a diff a few months before that.

Follow the time line of my posts. I was posting messages as I was doing the project.

83 Crossfire TA

iTrader: (2)

how far toed out? I'd actually be a little suprised if you could get it right with a press, it would be easier to use a rosebud tip on a torch and heat the front of the axles till they pull forward some, which is not going to be easy with the brace on.

generally the axle tubes can get pulled far enough to trash bearings or cause spline wear before the alignment becomes a real problem.

AlkyIROC

I never did get around to trying to straighten the housing. I had no problems all last year. The car went straight down the track every time. I never pulled the axles this winter to check splines etc.

According to the alignment rack readings, the rear diff toe out almost 1/4". With the large slicks is probably why it's not noticeable.

83 Crossfire TA

iTrader: (2)

Holy crap! ¼” is a lot of toe out, just think of how big a curve you have to have in the axle tubes to end up with the flanges on the outside to be off enough to have a ¼” toe out. Actually, funny but it works out to each axle end being something on the order of ¼” off (1/2” total between both sides), that’s a huge problem and I wouldn’t be surprised if it was enough that it even causes traction problems.

AlkyIROC

1/4" out means each wheel is pointing outward 1/8" which isn't very much. 1/8 + 1/8 = 1/4. Zero would be perfect. As I said, it was almost 1/4" so each side is actually less than 1/8" out.

There's no abnormal tire wear on the slicks.

83 Crossfire TA

iTrader: (2)

right, measured at the rim...

you almost never run toe out on most cars, front or rear, and have you ever driven a car with 1/16" toe out on the front at speed? it's hard to keep it going forward in a straight line...

AlkyIROC

Front end alignment is totally different. The toe on my front is zero.

chris.niemann84

i know this is like 2 years later, but its pouring rain on an Easter Sunday so I'm going through reading a lot today cause I'm bored! anyways, I have an 85 with a 350... and my fat *** in the seat sitting at 3750 on the scale with a little over half a tank of pump gas (and literally everything inside and T Tops)

Like i said, i'm bored

AlkyIROC

My race weight last year was 3042. I'm changing a few things again and won't know what the race weight is until I get across a scale. I'm still trying to get under 3000 pounds. Strip out a little bit more but end up adding in more stuff.

The aluminum center section and spool are in and I'm in the process of changing the cage although I can't see that making a huge difference in weight. It may actually add more weight because of the few extra bars I want to add in. Adding the parachute puts a few more pounds onto the car.

When I put in the aluminum center section, I also straightened the diff although it hasn't been on an alignment rack to see how the 4 wheels are aligned together. Can't be any worse than what it was.

This thread on doing the back half is also on my web page without all the extra comments.

chris.niemann84

it's ok, i like comments! LOL i'd love to get this car under 3500 with driver & 1/2 tank, but its also my daily driver (sucks on gas!!!) and my fiance is always with me everywhere and she "has to have a/c" along with a few other weight adding bs components... LOL. Oh well, its a camaro through and through and I love the **** out of it and can't ask for anything more!

maybe i'll get lucky and find out the scale was off............

thecamarokidd

wow that car is so sexy, thats what i want to do to my car, where did you weld the frame rails to? i been building cars for years but i never tubed out a car or anything like that but i want to do it to my camaro, probably the hardest car to do so since you need to make a frame. where do i start? i am putting a shortened for 9 in the rear.

AlkyIROC

The front of the frame rails are welded to a crossmember that's been welded between the front control arm mounts. The back of the frame rails are welded to plates which as welded to the sheet metal at the rear of the car. None of that sheet metal is flat so gussets are required to get it all square.

The "easiest" way to do it is to just buy a back half kit specific to the car. Welding is still required but the kit will be a better fit than the way I did it.

I changed the cage since the back half was done. The cage in the pictures wasn't good enough to pass a chassis certification and I also didn't like where I positioned the bars. You can find a thread about changing the roll cage to see what I did to put in the new cage.