This really sucks. Sorry man.

I am thinking you either leaned it out big time or you spun a bearing and with the tight PTV clearance that piston whacked the valves and started the destruction.

Did it happen during the run or when you were zinging it during a burnout?

 

Ya know, it is what it is. I hate it too but at the end of the day, I can’t be mad at anybody but myself for not data logging while at the track. And that’s just part of racing.
I wish I could say what it was, maybe it went lean, can’t know because I didn’t log. Maybe spun a bearing, can’t know cus how could you?
What I do know is that I made 3 passes and each one of them it did the same thing at different parts of the track. Somewhere before it would shift from 2nd the 3rd it sounded like it was banging the rev limiter without being near the rev limiter (6350rpm). I had my shift points at 6150rpm. The first time it happened I let off and coasted, the second time I let off but got back in it, the third time I let off and got back in it, and when I crossed the 1/4 mile mark it lost all power/shut off and threw up a cloud of smoke. Engine was locked at that point.

 

Small details are something I get really fired up about. I spent my Sunday working on making my interior a little nicer. When I installed my trans controller I just velcroed my control unit to the breadbox delete panel. During the summer months the Velcro would melt off and the whole thing was just super flimsy. So today I recessed it into the panel. Basically just dremel cut a hole and used epoxy to adhere it to the back of the panel. I also did the same thing with an angled gauge pod for my new AEM wide and gauge. I think it turned out really nice and can’t wait to see it in the car.

 

Man, I have been waiting and waiting on my engine to be built. Of course, I’m also impatient so it is what it is. I am sure it will be ready soon enough. However, in the meantime, I began working on the suspension modifications that I have been planning since the beginning. It’s funny because when I first thought about air bagging the suspension on my 84, nobody else was talking about it. But through the time that I have been planning, others have started the process. But nobody has finished yet. And I guess I haven’t finished yet either, but soon I’ll be done.
My plan was to always add air suspension while also trying to keep the performance aspect of the car. I knew that this was a tall order and so I did a lot of research on how to alleviate the issues. I decided that I would need to use double adjustable shocks to compensate. So I chose to go with Viking Performance shocks. Another aspect was that the air management system had to be too notch. AirLift Performance has been named a few times when it came to performance air suspension. So I decided to use the 3H system which utilizes height sensors to keep the pressures accurate as the car goes through different g forces.
I knew the hardest part for me was going to be how to place the bags within the suspension for optimal performance.

I decided that I would use the original suspension pieces as much as possible and just weld mounts on to those. Once I figured out the plan, I sent my parts off to my welder and began working on mounting the air management system.
I want to keep all the interior space usable, so finding a place for a 5 gallon tank and 2 Compressors seemed tough. I ended up making a bracket that bolts into the spare tire carrier mounting holes. This bracket holds the 2 compressors and the tank under the car. Everything feeds into the drivers side storage bin where the manifold, wiring, and extra air line are kept.





As far as the suspension, I’ll start with the rear. I used 3” long brackets that clamp on either side of the batwing mounts and have a normal upper air bag mount welded to them. I needed to make sure they were offset just enough to avoid the bag rubbing on the halfshafts. The bottom bag bracket is a piece of 1/4” aluminum welded to the stock strut rods and gusseted for extra strength.







For the front suspension, I ended up pulling the K member off since I already had the engine out. We decided to weld an 11 gauge plate above the lower control arm bolt locations for the upper bag to bolt too.


And for the Lower control arm, 2” wide aluminum flat bar was welded to the arms. This allows the air bag to sit 1.5” deeper in to the control arm. And then we used 1/4” aluminum to be the base plate for the air bag. I can’t forget to mention that we used a plasma cutter to trip some of the inside of the control arm away, but we honestly didn’t need to.



I am finishing up the install of the suspension pieces this week and will try to keep you guys updated as I go. I still need to figure out the shock mounting plate but I think that I will be able to use the stock plate with some trimming.
My other concern is the front and rear sway bar mounting locations and trying to get the best travel for those with a good mounting system.

 

Incredible work man!

 

Got a bit further ahead on the air suspension this week. Finished the rear suspension and torqued all the bolts except for the camber bolt on the strut rod. Also finished the front but still need to torque the bolts. And I also ran the management system throughout the car.

 

Sorry I didn't see this update earlier, but you need to stop what you're doing right now and rethink that rear suspension. The spindle rod (lower lateral link) you're using to seat the airbag on was never meant to take the vertical loads of the unsprung mass! It was only designed for tension/compression loads to maintain camber as the car encounters lateral loads, and even then it's the halfshafts that take most of those lateral loads. The only part of the rear suspension that was designed for vertical loads is the knuckle, at the bolt that hangs from it to connect the spring ends and at the lower shock mounts.

To make matters worse, you've cantilevered the bag seat roughly 6" to the side of the spindle rod, meaning you're adding a huge moment arm (torque) around the rod that it's not designed to react. The link itself is just an I-beam, and those aren't made to resist torsional loads at all. But even if it were, the rubber bushings are specifically intended to allow the link to both twist and swing forward/backward to follow the arcs of the trailing arms.

The upper shock mount is part of the steel frame and it's the only other place in back meant to take the vertical loads from the unsprung weight of the car. I think the batwing frame mounts you've built will probably work for your upper mount, but I'm not even sure of that. The front lower control arm is a completely different story, because it only has to move in one arc and it is designed to take the vertical loads from the spring and shock. From what I can see, your front setup should work.

This setup you've created is probably going to fail as soon as you lower the car off the jack. I hope so, because if it doesn't then it will fail while you're driving it and the results are going to be ugly. By far the best way to implement an air spring in back would be to use the shock mounts in an "air shock" arrangement, but the problem is always going to be clearing the halfshaft with the bag. You'd need to find a bag or air shock with an out diameter of 2.5" or less, and then move it forward at the upper and lower mounts, as well as bracing the lower mount on the knuckle, like the good coilover kits do. I can't think of a good way to use the spring-end bolt as a lower bag perch without interfering with the shock.

I'm not sure why you decided to implement an air spring suspension. There could be some valid reasons for it, but let's be clear that performance is not one of them. Any air spring is highly progressive, and there's no good way for passive dampers to work well throughout their range of travel because the spring varies so much. It's not a coincidence that no road course race cars use air springs, ever. When it comes to handling with a passive suspension, you're always going to be far better off with a linear-rate spring like the monoleaf or like most (but not all) coils. Now, if you want adjustable ride height on the fly, air springs are obviously great for that.

 

100%
i too have just read thru this thread and the first thing that jumped into my head was the cantilever effect on the camber rod bushings. they will have such a load on them at such an angle, i can see them failing and being replaced on a regular basis, if this setup makes it that far.
my $.02 opinion.

 

As soon as the car comes off the jack, those plates are going to have roughly 2000lb on them (I'm visually estimating a motion ratio of 0.6:1 and that the car has about 1500lb of total rear wheel load). Those plates that form the bottom perch will tilt down severely and the strut rod will bind. I'm talking like a 30-degree angle, right away, or however much the bushings will allow. The rod, being aluminum, will probably permanently twist right away or soon thereafter. Eventually the spring bag will fail, or the bolt holds it to the perch will fail, or the rod itself will fail. That's assuming the welds between the steel plate and aluminum arm are good and they don't fail first. I seriously hope the car isn't moving when that happens.

 

X3, here.

You've done a LOT of hard work.....but I don't think it's safe at all....never mind good handling/functioning.

I agree that the front lower arm looks O.K.....but I wonder about the effect of welding on that forged aluminum arm. Is that detrimental to the arm's strength?

Could the OP mount the rear air bag on TOP of the rear knuckle in the location where the stock spring bolts go, and the straight up to under the rear frame rail?
EDIT: No, it's inside the ID of the wheel and outside the frame rail.

.

 

The moment exerted on the aluminum camber rods by the lower bag mount will be huge. The camber rods are mounted with rubber bushings. This air bag rear suspension will result in catastrophic failure in very short time.

Not good!

 

More twisting imposed on that rear camber rod and attachment than it can handle, and there are a lot more issues with that rear design, trying to load the attach points in torsion, the single shear welded aluminum plate with tremendous leverage, etc.

 

Thank you guys for all of your great advice. Each of you know exactly what will happen, or would have happened if I were to have put that on the street. I am still waiting for my new LS build to be built so I had the luxury of testing all of the suspension pieces before ever actually taking it off the jackstands. So, as predicted, the strut rod could not take the torsional load and just twisted inside the spindle mount. I’ll attach some pictures. I wish I had read y’all’s comments but I didn’t.

As you can see, it did exactly what you predicted. When I saw this, I thought, “oh, there’s just not enough support under the flat plate”. So I welded some more support to the bottom side of the plate but as you could guess. And like I mentioned, it just twisted in the spindle.


Luckily, I have spare strut rods to go back to the factory setup.

So I went back to the drawing board…I think I have come up with a solution. I am going to use the factory spring mount location to support this setup.




this will be able to be in line with the factory suspension components. The middle part will bolt in the spring mount location on the differential cover, and the end of the arms will have the long bolts that went through the spindle to the end of the spring bolt through them. The lower bag bracket will be welded on top of the arms which should, in theory, keep all the original geometry.

Thank you again for you words of advice, I just wish I had seen them earlier. But that’s part of designing stuff that is new, never/not often done. I do know some of you have your concerns about air bags performing worse than the factory suspension in competition. I understand your concerns and don’t disagree with you, I just have a bit of a different goal/vision for my Corvette. Plus, I really enjoy designing and building things that aren’t often done.

 

With different suspension pivot points (camber rods vs your new bag mount pieces) the end links (previous transverse leaf spring end mounts) will be moving in an arc.

 

First, let me say that we all learn from our own mistakes, but it's really helpful when we can learn others' mistakes too. So I applaud your: 1) not getting defensive, and 2) posting the learning.

If I understand the new plan, the new arms pivot on the inside at the stock spring mount under the diff, and the outboard ends are supported by the hanger bolts for the stock spring. Then somewhere in the middle you'll have a lower spring seat for the bags? And you're going to keep the stock camber rod in the stock location so that it and the halfshaft will still dictate the suspension geometry, right (this is important)? If so, this could work, but I'm going to give you a big suggestion in a moment. First, to address KSA Aaron's concern, the different arc shouldn't matter because this new arm will have no roll in locating the spindle/knuckle. It will pivot around a fixed point on the inside, but the long hanger bolts at each allow a lot of movement relative to the knuckle, so no binding. This would be just like the factory leaf spring. Assuming I'm understanding the plan correctly, that seems like it will work. It's actually an elegant solution that didn't occur to me when I was replying to this post before.

My big caution here is that you really need to think about and maybe consult a structural engineer for the design and construction of the two arms. I think your center mount section is probably fine. But going back to my second post about the original plan, you're proposing to place a roughly 2000lb vertical spring load right in the middle of each arm. I am not an engineer of any kind, but I'm guessing that the square-tube arms you have aren't strong enough for that task (I'm guessing 2" square, mild steel, 2' long?). You'll want more vertical web height than the two vertical sidewalls of that tubing will provide. You don't need the arms to be strong in lateral bending (fore/aft on the car) or in torsion (but see the next paragraph), but they need to be a lot stronger in vertical loading. This is why manufactures use stamped parts forming roughly a U-channel for a spring-mounting LCA. See the pic of the stock 2016 Camaro rear LCA below. You don't need lots of vertical height at each end of the arm, but you need it toward the middle where the spring will mount because that's where the force is centered.



Next, you need to get the mount below the line of the two arm mounts so that the vertical spring force isn't always trying to twist the arm upside down. See the pic of the blue aftermarket Subaru control arm: the spring mount bolt (yellow) is significantly below the two arm pivot points (red line). The stock LCA above does this too, but it's easier to see in the pic below. This way, the spring's force is always trying to prevent the arm from twisting, rather than cause it to twist. Every control arm that carries a spring or shock load is always designed like this. Sometimes the vertical "webbing" gets taller and sometimes the arm is bent (sometimes both), but the spring mount is always below the pivots. This isn't option on any control arm, but it's super-duper critical in your case because this arm is dangling on the hanger bolt at the outside end and that won't provide any resistance to it twisting over at all. So you - even more than most - need the spring force to hit the arm low to provide a continual "righting moment."



This isn't going to be that simple to fabricate, unfortunately, but it's really important to get this right. It might even be worth seeing if you could "borrow" factory or aftermarket control arms from some other car and adapt them to your project.

 

Sorry it has been quite a while since I posted. I finished the suspension mods and could t really test anything until I got my engine back from the builder. Luckily, I received the new engine in July, got it installed by August and have been testing everything since.
I have come across a few small issues but have remedies each one that happens. To pick up where I left off, I finished rear suspension using the stock leaf spring mounting locations. Both at the diff carrier and the knuckle. Placed the bag on the pivoting arm. The only real issue that I ended up having with this setup was that the upper mag mount started pivoting under hard acceleration which would smash my airline. It probably would also cause some differences in the handling. However, I welded a brace to keep it from rotating. Here are some pictures of the final setup.


The pivot arm mounted to the knuckle.

The pivot arm mounting to the diff carrier.

The upper bag mount and sway bar link.

Here you can see the added “post” bracing for the upper bag mount to diff carrier.

And finally, the mounting of the air compressors and tank. Everything hidden underneath the car.

 

Here are some updated pictures of the car.





Cars & Coffee

Aired out

This is the actual ride height of the car

Comparison of ride height and parking height.

 

Awesome thread, bookmarked for my ls-'84 build. I didn't see what you did tying the ecm with the stock fuse box. Any pics or insight?
Thanks, Brian

 

Hello again my fellow Corvette enthusiasts.
It has been quite some time since I last updated this build thread. So I wanted to give some updates and insights into my 1984 LS swapped and bagged C4.
As you may have read, I have done a lot of custom work on this car and it has continued. First, a little update on the air suspension. It’s been 2 years, and so far, I haven’t had a single issue with the custom built air suspension. In fact, I believe the car actually rides better than stock at this point. And it handles the added power through launching and twisty roads. The one addition I would like to do, and I have the stuff to do it, is to add the height sensors to the AirLift Performance management system. I currently just use the 3P which is a pressure based management system. The 3H uses height sensors to keep the cars ride height at whatever you set it as and it’ll adjust accordingly throughout the driving conditions.
I’m going to post some updates on specific modifications I have done in the past 2 years but here’s kind of a list of what I have done:
Installed new engine
Completed entire Stainless Steel exhaust system
Holley Terminator X Max install
Holley ProDash
8” Touchscreen radio
Infinity Taillights
LED fog lights
Im still trying to get the car to run cooler in the Florida summer heat as well. But that seems to be a work in progress at this point. lol 😂 anyway, next spots will have some more specifics on these updates.

thank you again for all the words of wisdom and encouragement.

 

Let’s talk about the new engine…stupid engines! Lol
As You have read, I blew up my junkyard 6.0 cast iron block after having heads and cam installed.
So the new engine is an aluminum block 6.0 this time. However, I did put a forged rotating assembly in, so forged crank, rods, and pistons. I installed fresh rec port LS3 heads (that’s why it’s a LS2.5). I also traded the Atomic intake in for a FAST intake. Added benefit was that I could easily get my wiper motor reinstalled.


So before I reinstalled the engine I had some upgrades to do. I decided to install headers but as you know, BRP wanted an arm and a leg for their C4 specific LS headers. Instead, I chose to go the hard route and bought gently used c5 headers off FB marketplace. Of course, they didn’t exactly fit the c4. I had to cut the collector right at the convergence point and weld new 3” flanges on. I decided to go full 3” stainless to the Borla mufflers. I also used the X pipe from the c5 exhaust I purchased. Sadly, the collector wasn’t all that needed to be cut and redesigned. The drivers side fit great. But the passenger side needed the first primary tube to be rerouted, and so we did.
Id like to also state, I am not a welder nor do I have those tools. So when I say “we” I mean my welder friend. Who just also happens to be in a wheelchair like myself. 2 crips building 1 shitbox. 🤣oh the joy.

Collectors cut and rewelded and the PS primary cut and rewelded

Here you can see why I had to adjust the primary tube. Also, heatwrapped

Custom 3” stainless mid pipes

Wow!! What a difference the headers and midpipes made in the overall sound of the car.