Bee Jay's Batwing install

I figured I need to move some of my projects over here. This is old but may still be helpful to someone contemplating doing this.
Bee Jay

I tried to add to a much earlier thread on this topic, but it is closed. Anyways, I finally started my batwing install this weekend. I have my trailing arms out, and I bought some offset trailing arms to replace them. They are off getting built up with new bearings.

But since I have half of the rear end out, I thought now would be a good time to do the batwing install.

Yep, While I'm in there, the start to most Corvette projects. I'll also mount the rear end an inch higher to lower the car and it's cg.

Removing the iron diff and crossmember was easy. I expected more trouble.
The batwing weighs 20 lbs. The iron cover and steel crossmeber weigh 35lbs, so I guess I'm only saving 15lbs.

Removing the stock rubber bushings from the aluminum batwing was a major pain in the a$$. But now I know how to do it. Press the rubber out, hack saw a groove in the steel sleeve, and then chisel them out.


I built a tool to temporarily mount the rear end in place while I build and weld in the brackets. This tool allows me to finely adjust the height of the rear end and the batwing can be removed out of the way when it's time to weld in the brackets. You can see that the original crossmember brackets are in the way and will have to come out. I hope my sawsall can handle that. There will be no turning back, there will be nowhere to mount the original cross member.





More later.
Bee Jay
The brackets are built and in. My friend Gill, we call him the "Detail Man" took Twin Turbos CAD and about a thousand measurements on my car, and designed these brackets. My friend Norm, with MAD welding skills, welded the brackets in. They are very elegant and strong. Check them out.
Hey, can somone please tell me the torque specs for the batwing cover bolts to the rear end.
Bee Jay





Bee Jay

spedaleden said:

Bee Jay very nice work. Just wondering why are you going through all this?

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Because it's there:rofl:. Also, I think it looks cool.
It's another "while I'm in there" job, I had to remove my trailing arms to have the guts transferred to my new offset trailing arms, so I might as well do the batwing conversion while I'm in there. Actually I was hoping to raise the rear end 1" and lose about 50lbs. I ended up raising the rear end only 1/2" and I will lose 35lbs. To raise the batwing/iron rear end a full 1" higher than the original location would require modification of my hatch area floor and notching my frame for clearance. I had to trim the batwing top even with the iron rear end cover top. That gave me another 1/4" to raise the batwing. Raising the batwing to within 1/4" of the floor and 1/4" of the frame resulted in the 1/2" rise. The aluminum batwing is only 15 lbs lighter than the iron cover and crossmember, but I eliminated the crossmember that supported the rear end crossmember, just like GM did in 1980. Check this thread:
http://forums.corvetteforum.com/c3-...s-this-frame-crossmember-still-necessary.html
That crossmember weighed 20lbs. So I lost 35lbs. Here is the nose mount modified to raise 1", the washers are there to bring it back to 1/2" rise.

Bee Jay
The batwing is in and solidly mounted Sunday evening. After that I got the driveshaft in and called it quits. It was getting cold and my Cowboys were comming on. I'm going home to Texas for Christmas Thursday, so I'll mount the offset trailing arms and finish this whole project maybe for New Years. I want to buy and burn some of this $1.80 a gallon premium. can someone please tell me what to torque the batwing cover bolts to the rear end.
Merry Christmas everybody.
Bee Jay


I'm back from my Christmas vacation in San Antonio Tx. It's a good thing I'm saving 35lbs with this batwing install, cause I just gained 20lbs. I got to work on the car a good nine hours today. Taking stuff apart goes much faster than putting stuff back together again. I had to raise the diff 1/4" and raise the tranny mount 3/4" to get the crank/tranny parallel with the rear end. Installing the offset trailing arms was a lotta fun, especially the bolts and alignment shims. It's important to know, the batwing mounts the leaf spring with a 3 hole plate instead of the original 4 hole plate. You must have a 3 hole plate and the needed bolts to mount the spring properly. I sure would like to know how you concours weenies put your cars together without chipping the powder coat or scratching the paint. I filled the diff with 2 pints of Valvoline synthetic gear oil. I need to bleed the brakes and hang the exhaust. Maybe tomorow after church, but the Cowoys are playing maybe their last game of the season. I need to get the car back in the garage before the rainy season gets here. Here's a pic. That batwing looks kinda cool in there. Removing that uneeded crossmember opens things up a bit too.
Bee Jay

OK, it's done. Here are some pictures just before I take the car down. Everything is bolted up except the sway bar. I took it for a spin and everything works. The only problem is that the right side is 1" higher than the left. I measured at both the frame and the top of the wheel well. I crank the left spring nut about an inch, but it's still not level. And it looks unprofessional with one nut at full extension and the other cranked way up. No problem. I put the car back up on the lift, and I swap ends on the spring. That should either solve my problem or make the right side low. Well, I let the car down, take it for a spin, and the left side is still low. I think I can move the spring over a 1/4" inch or so, and equalize the ride height. I need someone to do the Physics and Geometry. Which direction do I move the spring to bring the left up, or the right down?
Bee Jay

FatCat Blue 80 said:

Bee Jay,

I always enjoy your projects as you always provide great tech for the rest of us to learn as you learn and enjoy. Great job:thumbs:

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Thanks FatCat. I ask about a million questions around here and on the other Vette forums, so when I do something, I know what I'm in store for. I try to document my projects, especially the difficulties and discoveries and with pictures, so that the next person to try will be better prepared. I do the same thing on the Porsche and Ferrari forums. I have to be very careful, offer some bad or incorrect advice, and they humiliate you. But I appreciate the appreciation. You made my day.
Bee Jay

Well, I got the car down and running last weekend. I've since been driving it to work daily, and on Sunday, I drove it to San Luis Obispo with Sylvia as a passenger (About 130 miles round trip). Everything is working great, and with new wheel bearings and new trailing arm bushings, the cars comfort cruise zone has moved from 75-85mph to 85-95mph. Several times on the road to SLO, I looked down at the speedo and had to bring my speed down significantly. It tracks fairly straightly, so the alignment must be close, but I need to get it aligned and the tires balanced. The car ran just a little on the warm side, the water temp hovered at 220-230 degrees, and the oil temp was at about 190-200 degrees at highway speeds. I think those will come down significantly when I bolt the front spoiler back on. I need to build a couple of brackets so that I can mount my modified rear sway bar as close to the trailing arm as possible. The batwing brackets took about a 1/8" clearance away and my sway bar end link is rubbing against the frame. I get this strange squeak sound every time it rubs up against the frame and bracket. The rear is sitting one inch lower on the driver's side, and I will attempt to address that this weekend. But no noticeable frame flex from eliminating that crossmember. But I declare the batwing project complete and done. I'm 35lbs lighterThanks to Twin Turbo for his drawings and measurements, Gill for all his help and his bracket design, and his fabricating skills, and to Eric for his help and tools, and to Norm for his welding skills. Any one wanting to try this, feel free to ask me any questions.

What's next? Maybe I'll just drive it and wash and wax it for a while………..NOT.

I have this Edelbrock RPM Air Gap intake manifold on the shelf, and I think my computer controlled HEI has arrived. But if I pull the manifold and distributor, I only have to pull the water pump and timing cover to do the Hydraulic roller cam conversion. The roller cam is about $200 from Scoggins Dickey Chevrolet, but the conversion lifters are about $450. So maybe I will hold off on doing the Dist. and intake until I can afford the cam and lifters.

I definitely need to get some Magna Flow mufflers installed. Those stainless mufflers are expensive. But I can't hear what Sylvia is telling me while we drive to SLO. These Flowmasters would have been perfect when I bought the car at 21, but at 51, they are too loud. A C5 Z06 pulled up next to me in the Best Buy parking lot, I started to ask him if his engine is running? That's an old Harley joke, but I was actually jealous of how quietly his car ran, and he could prolly kick my Corvettes ass. Noise aint necessary.

Bee Jay

Bee Jay said:

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I definitely need to get some Magna Flow mufflers installed. Those stainless mufflers are expensive. But I can't hear what Sylvia is telling me while we drive to SLO. These Flowmasters would have been perfect when I bought the car at 21, but at 51, they are too loud. Similar opinion here. A few years ago I spent the weekend welding elbows and brackets to install a pair of Flowmasters on my car. I drove the car about twelve miles before I couldn't stand it any longer, and pulled the car back into the garage to pull the Flowmasters off. Just too loud, and a crappy tone to boot. Running some turbo mufflers on it now. Much quieter, and I like the tone at WOT. A C5 Z06 pulled up next to me in the Best Buy parking lot, I started to ask him if his engine is running? That's an old Harley joke, but I was actually jealous of how quietly his car ran, and he could prolly kick my Corvettes ass. Noise aint necessary.

Bee Jay

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I agree. I'm going to be welding up a new system this winter, and in addition to bigger pipes, I'm going to try a couple ideas to quiet the system down a touch. I like the present exhaust tone and volume at WOT, but I'd like to tone down the volume and tubing ring at idle and low speeds.

69427 said:

Bee Jay said:

...................
I definitely need to get some Magna Flow mufflers installed. Those stainless mufflers are expensive. But I can't hear what Sylvia is telling me while we drive to SLO. These Flowmasters would have been perfect when I bought the car at 21, but at 51, they are too loud. Similar opinion here. A few years ago I spent the weekend welding elbows and brackets to install a pair of Flowmasters on my car. I drove the car about twelve miles before I couldn't stand it any longer, and pulled the car back into the garage to pull the Flowmasters off. Just too loud, and a crappy tone to boot. Running some turbo mufflers on it now. Much quieter, and I like the tone at WOT. A C5 Z06 pulled up next to me in the Best Buy parking lot, I started to ask him if his engine is running? That's an old Harley joke, but I was actually jealous of how quietly his car ran, and he could prolly kick my Corvettes ass. Noise aint necessary.

Bee Jay

Click to expand...

I agree. I'm going to be welding up a new system this winter, and in addition to bigger pipes, I'm going to try a couple ideas to quiet the system down a touch. I like the present exhaust tone and volume at WOT, but I'd like to tone down the volume and tubing ring at idle and low speeds.

Click to expand...

That problem has since been solved with a simple X-pipe. Check it out here:
http://forums.corvetteforum.com/c3-...pe-crossover-installed-what-a-difference.html

I went through a couple exhaust iterations a few years ago in an effort to quiet the system down. I added a crossover behind the trans crossmember, but that didn't work as well as I hoped. I then added another crossover underneath the differential. The noise reductions just weren't very significant. After lifting the pipes in and out while I was doing this, I noticed that they were quite heavy (they were stainless pipes). So, in addition to trying to quiet the system down, I also wanted to reduce the weight if I could. Doing some calculations, I noticed that a 3.5 inch pipe had essentially the same internal volume as two 2.5 inch pipes. But, the 3.5 inch pipe only has about 70% of the wall material (and weight) of two 2.5 inch pipes. Additionally, I had kicked around the idea of adding plenum area to the system to dampen out the exhaust pulses. So, the initial design was:



I built the system in mild steel, as it was easier to obtain the mandrel elbows, along with the wall thickness ending up being somewhat thinner. The result turned out to be ten pounds lighter than the stainless dual pipe system. The exhaust note at idle is very different from some "true" dual systems, in that the pulses are obviously equal on both pipes (twice the frequency), but are reasonably subdued in sound and pressure.
This winter's upgrade will be a three inch system, incorporating a large common plenum as before. I've got a couple other ideas I want to try, but I'll just have to try them first before I make any claims regarding their effectiveness.