MG Sports Cars

engine swaps and other performance upgrades, plus "factory" and Costello V8s

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rficalora
Rob Ficalora
Willis, TX
(2540 posts)

Registered:
10/24/2007 02:46PM

Main British Car:
'76 MGB w/CB front, Sebring rear, early metal dash Ford 302

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Who's done the modification to make the rear cross member removeable?
Posted by: rficalora
Date: May 12, 2018 07:36AM

I'm thinking about and looking for ideas of ways to do it where I wouldn't have to remove the seats & carpet when welding. The way I've seen it done, the cross member is cut out, a plate is welded to each end and to each end of the piece removed, and it's then bolted back in.

I'm concerned that the heat from welding the plates on the ends will melt the carpet &/or be a fire hazard. So, I've been thinking about other ways to do it. One idea is to make sections of U-channel that are a snug slip fit inside the cross member. Weld the plate to that and bolt that assembly to the cross member. The cross member is pretty thin, but I'm thinking I'd use 16 gauge for the u-channel sections for strength.

Anyone have a better idea?


ex-tyke
Graham Creswick
Chatham, Ontario, Canada
(1031 posts)

Registered:
10/25/2007 11:17AM

Main British Car:
1976 MGB Ford 302

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Re: Who's done the modification to make the rear cross member removeable?
Posted by: ex-tyke
Date: May 12, 2018 09:14AM

Here's another approach which might be carpet friendly....Bill Guzman's tubular xmbr from the British V8 photo gallery.
Guzman MGB xmbr.JPG



Edited 1 time(s). Last edit at 05/12/2018 09:15AM by ex-tyke.


rficalora
Rob Ficalora
Willis, TX
(2540 posts)

Registered:
10/24/2007 02:46PM

Main British Car:
'76 MGB w/CB front, Sebring rear, early metal dash Ford 302

authors avatar
Re: Who's done the modification to make the rear cross member removeable?
Posted by: rficalora
Date: May 12, 2018 09:27AM

I'd seen that Graham. It's welding the plates that cap off the cross member sections that remain on the car and become what that middle piece bolts to that concerns me.


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(5648 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

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Re: Who's done the modification to make the rear cross member removeable?
Posted by: BlownMGB-V8
Date: May 12, 2018 09:44AM

Bill's design is pretty good. It's also possible to tack the nuts on. I've used thicker plates and tapped them. I've also used square tube with a thick enough wall to attach a transmission mount to it.

As far as your welds are concerned, you are not going to be able to weld the top, just the sides and bottom. So the only place you need to worry about it is at the top of the sides and you have a layer of sheet metal between that and your carpet. Just do short tacks there and let it cool. The rest won't be a problem.

Jim


40indianss
don foote

(37 posts)

Registered:
08/01/2013 04:35PM

Main British Car:


Re: Who's done the modification to make the rear cross member removeable?
Posted by: 40indianss
Date: May 13, 2018 10:18PM

Reuse the piece that was cut out. Weld a piece of 14-16 gauge on each end and front and back side. Drill two 5/16-3/8" holes into the tabs where they overlap the remnants of the original crossmember, mark the holes for drilling. Make four tubular sleeves about 2" long with 5/16 or 3/8 I'd. These will have an od about 1/2" so drill that size hole in the four marked holes in the crossmember remnants. Insert the four sleeves into each hole and weld into crossmember then grind smooth. Insert removeable section so four bolts can be inserted into sleeved holes and overlapping tabs on removeable centerpiece. Tighten nuts and bolts and done. The sleeves will prevent crushing the sheet metal crossmember from over tightening. The centerpiece is now easily removeable when removing the transmission without the hassles of the original crossmember


MGBV8
Carl Floyd
Kingsport, TN
(3497 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
79 MGB, Buick 215

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Re: Who's done the modification to make the rear cross member removeable?
Posted by: MGBV8
Date: May 14, 2018 11:08AM

Stock fixed crossmember:

Stock Fixed Crossmember.JPG


MGBV8
Carl Floyd
Kingsport, TN
(3497 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
79 MGB, Buick 215

authors avatar
Re: Who's done the modification to make the rear cross member removeable?
Posted by: MGBV8
Date: May 14, 2018 11:08AM

Removeble fixed crossmembers:

BillGuzman

Bill Guzman Crossmember.JPG

Hank R

Hank R Crossmember.jpg

Grant70B

Grant70B Crossmember.JPG

Jimmy N

Jimmy N Crossmember.jpg



Edited 1 time(s). Last edit at 05/14/2018 11:10AM by MGBV8.



rficalora
Rob Ficalora
Willis, TX
(2540 posts)

Registered:
10/24/2007 02:46PM

Main British Car:
'76 MGB w/CB front, Sebring rear, early metal dash Ford 302

authors avatar
Re: Who's done the modification to make the rear cross member removeable?
Posted by: rficalora
Date: May 14, 2018 02:55PM

What Dan describes & what Jimmy N did are along the lines of what I was thinking. But Jim B has me re-thinking about how much the welding heat would be a problem. Will decide which way I go when I get the car up on the lift & have another look at it but leaning toward the traditional approach. Makes for a cleaner looking solution.


MGBV8
Carl Floyd
Kingsport, TN
(3497 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
79 MGB, Buick 215

authors avatar
Re: Who's done the modification to make the rear cross member removeable?
Posted by: MGBV8
Date: May 14, 2018 03:41PM

Not sure that it is really needed, but Dan & Jimmy's approach could also be done with rectangular tubing that has the top notched on each end.


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(5648 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

authors avatar
Re: Who's done the modification to make the rear cross member removeable?
Posted by: BlownMGB-V8
Date: May 14, 2018 06:43PM

I like the appearance of that last one, best to size it so that it can spring out just a little when it is unbolted. That will make it easier to fit up. The spacer tubes are a necessity with that design. I'd close the top.

Jim


74ls1tr6
Calvin Grannis
Elk Grove,CA
(1144 posts)

Registered:
11/10/2007 10:05AM

Main British Car:
74 TR6 / 71 MGB GT TR6/Ls1 71 MGB GT/Ls1

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Re: Who's done the modification to make the rear cross member removeable?
Posted by: 74ls1tr6
Date: May 16, 2018 02:16PM

Rob, my setup is a little different because that crossmember is my transmission mount. But if you do your cut right, you would be tack welding in the tunnel area of your driveshaft . 3 tack welds right next to each other, like laying quarters, then have your air hose to cool right after, then repeat.


You may have seen this when you have come over on Brenda's GT. The box is made out of 1/4" plate for the T56. But for welding you get the idea.
IMG_20180516_111057.jpg

IMG_20180516_111040.jpg

IMG_20180516_111107.jpg



Edited 2 time(s). Last edit at 05/16/2018 02:30PM by 74ls1tr6.


rficalora
Rob Ficalora
Willis, TX
(2540 posts)

Registered:
10/24/2007 02:46PM

Main British Car:
'76 MGB w/CB front, Sebring rear, early metal dash Ford 302

authors avatar
Re: Who's done the modification to make the rear cross member removeable?
Posted by: rficalora
Date: May 16, 2018 02:19PM

Wait, those pics imply you're actually making progress on Brenda's car... Could it be true?


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