Fabrication of Rear Chassis Extension per MGB V8 Book

Robert J · June 21, 2012, 03:48:42 PM

Hello All;

I am elbows deep in to my V8 MGB build. The engine I am installing is pretty powerful (331 stroker, 9 to 1 compression) so I would really like the added confidence offered by installing a set of rear chassis extensions as shown on Pg. 128 of the MGB V8 book.

Now, I know a lot of talk will go back and forth about weather these are needed. In the end, I think it is small insurance for the added stiffness.

My question is, who the heck can bend a set of these for me? I live in an industrial area with literally dozens of sheet metal bending shops. Every one of them cites reasons why they can't or won't bend these for me. The main issue seems to be the distance between one bend and the next not allowing enough room for the bending brake to fit.

Any ideas, suggestions or especially suppliers would be appreciated!
MGB stiffener.jpg

Jim Stabe · June 21, 2012, 04:12:15 PM

Robert

I can't read some of the dimensions on the scanned drawing but looking at the general shape, the shops are likely having an issue with the height being greater than the width. I am assuming that they would be using a press brake to do the job and the 2nd edge at the bottom would cause the already folded edge to hit the upper portion of the die. This problem can be overcome with offset upper dies but not many shops will have them. The way I would make the part is to do it in two pieces and weld them together. I would probably make the weld seam at one of the lower corners since it would be easy to dress out after welding.

This is a standard die set

An offset set like this would allow the part to be made

Good luck

Jim

rficalora · June 21, 2012, 04:19:01 PM

Use some wood & clamps & bend yourself.

Or, get some 1x2 or 1 1/2 x 2 box section & use it instead of the bent sheet metal.

The latter is what I did. I think it was 3/16" thick if I recall - could go a little thinner; thicker is just heavier. I plug welded to the floor about every 6" and seam welded it at the ends to the existing cross member & spring hanger.

ex-tyke · June 21, 2012, 04:24:45 PM

Contact Ted Lathrup at Fast Cars Inc
http://www.fastcarsinc.com/

Ted has a quality part that is pre-bent, trimmed to fit the MGB chassis irregularities and ready to weld in. Here's a photo of Ted's product tacked welded to my car before final welding.....

MGB chassis reinf 1.jpg

Robert J · June 21, 2012, 05:07:45 PM

I have been considering fabricating it myself of course, it would just be nice to have one with all the bends done. I'll check with Fast Cars. If the cost is too great, I will fabricate them.

Thanks everyone.

Jim Stabe · June 21, 2012, 05:08:11 PM

After seeing Graham's picture, I agree with Rob and just use a piece of rectangular tubing.

Robert J · June 21, 2012, 05:16:49 PM

Well, the initial design as shown in the MGB V8 book has a lip on the edge that is useful for welding to the floor pan. It can also be made to lay up and on to the Chassis center beam in such a way that the welds would offer more strength than if standard rectangular tubing was used. If made correctly, it would be better than rectangular tubing. I am not sure that the Fast Cars option includes the overlap on the front of the leaf spring perches either.

kstevusa · June 21, 2012, 09:14:03 PM

Wow! That is the part I call the sub-frame connectors. I did these years ago and have been very pleased with them. Mine are out of 1X4 square tubing and attach to the spring hangers and the center X-member and welds to floor. Graham, thanks for picture, I had no idea what was being discussed.
subframe connectors.jpg

mgb260 · June 21, 2012, 10:53:20 PM

There are Jeep floor mount repair channels that are flanged also. I also like what Geoff did between floor and firewall.

Here is where to get the channel: http://stores.ebay.com/PARKER-METAL-PRODUCTS?_trksid=p4340.l2563

Robert J · June 22, 2012, 01:07:09 PM

Great Stuff! Now I know what I am working on this weekend.

mgb260 · June 22, 2012, 06:19:08 PM

Robert, Document and pictures here!

rficalora · June 22, 2012, 11:03:38 PM

Kelly, those pictures look familiar. I think I must have stolen the rectangular tube idea from you.

Robert J · July 02, 2012, 01:31:28 PM

I just placed an order for rectangle stock. I'll follow up shortly.

flitner · July 02, 2012, 04:03:29 PM

I used 2x3x3/16 rectangle tube on mine, not so much for body support as the truss built into the rockers is a very strong backbone in itself, but the tube gave me a mounting area for the trailing arms of the 4 bar.

mgbazza · July 08, 2012, 09:33:51 AM

Bob, don't feel bad about "stealing" the rectangular tube idea from Kelly because he "stole" it from me ! Barrie E

kstevusa · July 08, 2012, 01:40:03 PM

Barrie, thanks, but you will notice they are totally opposite your design. Since the water swirls counter-clockwise up north, it required reverseing. your design only works where water swirls clockwise

. Seriously, I could tell immediately when I dropped the car and began the test drive there was positive change and the car felt more solid. Thanks from the sweltering southeast USA.