C4 batwing to fit my C3 differential

[69427]

Making slow progress on getting the C4 batwing modified to put on the '69. This batwing is about 7 pounds lighter than the C3 batwing currently on the car. Here's the (not yet finished) adapter ring (3/4" aluminum), and the batwing has been drilled out for the C3 pattern. Still need to weld up a couple of the original C4 bolt holes.



I need to narrow the batwing 2 1/4 inches to clear the narrowed C4 suspension in the car. I grabbed a bunch of old steel remnants and welded up a temporary jig to hold the outer mounts in place while I cut the batwing and reposition the mounts inward 1 1/8 inch. Not seen in the picture, but I used the threaded holes at the outer mounts that would otherwise hold the dampening weights.



Here's the outer mount moved inward 1 1/8 inch. I now need to clean up the cut and start welding the pieces back together.



The adapter ring is 36 ounces (additional weight), and the stock C4 spring bracket is about a pound lighter than the steel adapter bracket I currently have on the car (to be able to use the '84 Z51 spring). I should be able to lose an additional pound or two by now being able to use the toe mounts cast into the C4 cover, rather than the steel adapter bracket I had to fabricate to attach toe links to a C3 cover. I might also be able to use shorter/lighter spring hanger bolts with this batwing (won't know until later). All in all I'm looking for about a seven pound net weight reduction off the car. The reduction is down low and way back unfortunately, but it's still mass that won't be there needing to be accelerated and decelerated.

 

[BBShark]

How will you keep the heat (from welding) from burning the bushings?

 

[69427]

How will you keep the heat (from welding) from burning the bushings?

Well, right now I'm just planning on welding small sections at a time, primarily to keep the heat induced expansion/distortion to a minimum. It looks like the stock bushing has a steel sleeve around it, which I hope will help keep the large bore round. And finally, most likely I'll pop in a poly bushing setup afterward. For what ever reason, I've got a spare poly bushing setup that's been gathering dust on the shelf for probably the last 20 years. Glancing at the rubber bushings it looks like it's going to be a PITA to extract them though.

 

[rtj]

You could put batwing on the adapter if you used a wider piece of al plate. But you'd need a mill to cut the webs. Much safer to use billet than weld (what looks like) a casting.

 

[69427]

You could put batwing on the adapter if you used a wider piece of al plate. But you'd need a mill to cut the webs. Much safer to use billet than weld (what looks like) a casting.

I appreciate and share your concern for safety. I'm trying with all the modifications to not make my antique any less safe than it was when it was new (not a terribly high bar, I admit). I've been running a similarly narrowed, but C3 model, batwing in the car for the past six years with good results. The area I'll be welding is similar in width and thickness (similar square area) to the piece on the car, so I'm hoping for similar positive results.

 

[Twin_Turbo]

Just holesaw out those rubber bushings then with a die grinder slit the metal outer sleeve and hammer them out. Dress the bore for a chamfered radius and hammer in some urethane bushings, That way you won't have to worry about the heat.

 

[rtj]

You could put batwing on the adapter if you used a wider piece of al plate. But you'd need a mill to cut the webs. Much safer to use billet than weld (what looks like) a casting.

I appreciate and share your concern for safety. I'm trying with all the modifications to not make my antique any less safe than it was when it was new (not a terribly high bar, I admit). I've been running a similarly narrowed, but C3 model, batwing in the car for the past six years with good results. The area I'll be welding is similar in width and thickness (similar square area) to the piece on the car, so I'm hoping for similar positive results.

Can't you mill 7 lbs off the old batwing? It must be pretty beefy to weigh more than the wider c4.

I was just commenting above about safety as it was a race car or weekend race car and driver. If the batwing breaks your spring probably digs in and it would be bad for you and competitors.

Oh never mind, I see the old one is welded too.

 

[84rzv500r]

after welding if you were concerned you could just box in the ends of the batwing with a couple of pieces of 1/8 sheet alu... should be plenty strong... :bounce::bounce:

 

[69427]

after welding if you were concerned you could just box in the ends of the batwing with a couple of pieces of 1/8 sheet alu... should be plenty strong... :bounce::bounce:

We're pretty much on the same wavelength here. I was planning on adding some additional material bridging the weld area but I hadn't gotten far enough to figure out the configuration yet.

 

[69427]

New bolt pattern bolt-hole question

I've got most of the batwing mods complete (about 90% done with the welding), but have a question regarding the (newly drilled) cover holes that I did to match the C3 cover pattern. Most of the new holes are on the flat part of the cover, and my experience with aluminum parts (and I suppose other material parts) is that there is a raised island of material surrounding the bolt holes. I can speculate what the purpose of those islands is, so I'm trying to duplicate those on the cover. I've thought of cutting out some aluminum washer-shaped pieces and welding them over the bolt holes, or (and I'm not sure this would actually work) seeing if I can place a short length (quarter inch) of 3/4-1" diameter copper tubing around the hole and then MIG some material thickness inside the copper ring (and hopefully get the ring off after each weld). I'm just looking for some input/advice on this task.

Thanks.

 

[BBShark]

Would a washer of the same thickness (as the raised island) work? Is this to insure the gasket is not over compressed?

 

[69427]

Would a washer of the same thickness (as the raised island) work? Is this to insure the gasket is not over compressed?

I don't really have a good answer. I've just been curious if this raised section surrounding the bolt holes is there to radially distribute the clamping force better, or if it's there to be a sacrificial material to be lightly chewed up when the washerless bolts are spun into the bolt holes.

(As I've said in a few prior posts, I'm just an electrical guy playing with stuff that I'm not really qualified to mess with. :wink: )

 

[Grampy]

The raised area around bolt holes are typically found on cast components where the draft in the cast surface would create a slightly tilted clamping surface and induce some bending in the fastener. The raise areas can be spot faced (or cast without draft) perpendicular to the bolt holes to eliminate this undesired bending.

If everything is flat and perpendicular just add a washer and bolt it up.

Grampy

 

[69427]

Made a little more progress on the batwing. Got the ends welded back up, but still need to drill and tap a hole for the lube fill port. Probably will do it in the area just above the spring arc and below the lower two threaded holes for the toe-rods. That's pretty close to the same level on a C3 cover.



Still need to pop out the rubber bushings and install the urethane ones I've had gathering dust on the shelf. Also, I need to do a little more grinding/cleanup in a couple areas, and then a light sandblast to even out the texture between the cast area and the welded/ground/sanded areas.

So far it still looks like 6-8 pound weight reduction compared to the present C3 batwing and toe-bracket on the car.

 

[Twin_Turbo]

Those busings are a bitch to get out. Easiest is to drill holes through or holesaw. Pop out the center pin then the bushing and cut a slit in the shell and chisel it to collapse. Chamfer the batwing and pop the urethanes in.

Sent from my GT-I9505 using Tapatalk

 

[69427]

Got the exhaust system pulled out, along with the spring, toe rods and camber bracket removed. I welded up a few lengths of scrap tubing and angle iron to make a bridgework to support the differential in its current spatial position, and then took my sawzall to the batwing brackets on the frame (so I'm reasonably committed now). I just need to drain the lube now and I can unbolt the C3 batwing.

So far it looks like the net weight reduction should be about 10-11 pounds. Five pounds coming from the C4 batwing, and another 5-6 coming from not needing the steel adapter brackets to bolt up the C4 spring and C6 toe rods to the C3 batwing, and a slight material removal to make the camber bracket fit the C4 batwing.

Recently had Windows Hate point One installed on my computer, and now I can't get any pictures downloaded from my camera card, but I'll get some posted when I get the damn system issue figured out.

 

[Sam Cogley]

What's the camera problem? I've had good luck with 8.1 and 10, might be able to help if I have some more details.

 

[69427]

What's the camera problem? I've had good luck with 8.1 and 10, might be able to help if I have some more details.

I appreciate it. Presently when I plug the camera memory card into the slot on the tower, I get a full greenish blue screen saying how many files it found, this screen lasts for about 3/4 of a second, and then the screen changes back to the main screen with all the usual icons and shortcuts. No opportunity to look things over or store or delete things.
Previously, the card would download and the screen would contain all the pictures that were in the card. I then had plenty of time to label, date, and store the file in the picture section.

Just a bit annoyed and mystified why things can't be simple when it was only a modest software update.

Thanks again for any help.

 

[Sam Cogley]

Have you tried going to File Explorer to see if the card shows up there? It should be an option under the start menu. If that doesn't work, and the camera has a USB port, you could try connecting the camera to a USB port on your computer to see if it will show up as an external drive in the File Explorer.

 

[69427]

Have you tried going to File Explorer to see if the card shows up there? It should be an option under the start menu. If that doesn't work, and the camera has a USB port, you could try connecting the camera to a USB port on your computer to see if it will show up as an external drive in the File Explorer.

Went to File explorer and found the pictures in the G file. Thanks. Now I just need to figure out what's involved getting them all in a single date file.