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MG MGB Technical - Floors,Sill,Rockers.....oh my!

Hi folks

I'm a long time watcher and first time poster. This is my first MGB resto. My '75 is in need of alot of metal. The floors, cross-member, inner and out sill are badly rusted out. I have already removed the floors and crossmember. The car is supported in the middle by an adjustanle jack-stand.
My question to you is what should I do first? Install the floor and cross-member or the sills?
I haven't cut the sills out yet. I have all the parts primed and ready to go in...just unsure of the best sequence.

Thanks in advance.

Dave
D Stillie

OK, you have cut both floors out? The first rule of mgb restoration, one side at a time.

First thing you need to do is put the doors on the car. How are those door gaps? If they are nice and even things are good to go. If not, the body has shifted and is out of line. If that is the case you need jacks and stands all over the place to get the body straight again. The Bently manual has a diagram that shows you exactly how to straighten things up again.

Now, once you know the body is straight replace the floors and crossmembers than remove ONE of the sills and replace that before moving on to the other side.

You must measure and check at EVERY stage to make sure the body stays straight. Leaving the doors on gives and excellent quick check, if the gap changes something has moved.
The Wiz

Don't remember where I saw the pics, but after you get the door gaps right, weld a bar across the door opening on the inside (both sides). I went as far as to make an X brace for the inside to try to prevent twist as I rotated the body shell. I replaced/repaired the inner sills with the floor pan out. My inner sills were to the point that I had to make new pieces that contained the L shaped floor pan rest, so they had to go in before the floor. Not too bad a job if you like twisting yourself up like a pretzle and screwing yourself under the dashboard to weld.

Now I have a T project. Looks like all I need is a hammer and nails!

Tom
tom

Wiz:

Thanks for your quick reply. The body has squared up nicely with the help of the adjustable jack-stand in the middle, it did have a bit of a sag without it. Both doors are still in place too. The reason both floors are out is to replace the crossmember. Believe me the floors weren't adding anything to the structure of this car, that's how badly the were rusted!

Thanks again

Dave
D Stillie

Dave, it is vital to weld a brace in each door opening to hold the car in place. Jacks or stands is just not enough. Get the doors in perfect alignment and then weld a length of say 1 inch square tubing fron the inside of the A post to the inside of the B post at the top. Do this at the bottom as well to be sure that the opening stays square. Do the other side as well and I'd be inclined to cross brace for absolute rigidity. Bolted or clamped on braces are completely useless, but you only have to tack weld. With the car sitting on its wheels check that the gaps are correct. After that it's one side at a time for the sills but remove the cross member and replace at this point. Refit the floors last. Check the job at every step of the way. Lowering the car to the ground to transfer its weight to the wheels at frequent intervals is recommended to ensure that the doors still fit well. This is probably the single most important job on the B as failure to get this right will mean that the car will never be square.
Iain MacKintosh

Iain,

Is it necessary to brace the door opening on the GT body when doing the same work? I'm about to start.

Mike
Mike Howlett

I reccomend buying the book "Practical Classics Guide to MGB GT Restoration". Reasonably priced & full of information. Barrie E
Barrie Egerton

D:

Not near London Ontario by chance?

Pete
Pete

Thanks for all your help. The welded in braces sounds like a good tip.
I'm from Burlington Ontario BTW.
D Stillie

Mike, strictly speaking it's not but when you remove the sill there really isn't much left. I always go for belt and braces to be safe. It's not much of a task and it gives you peace of mind, besides if you weld the brace on the insides of the A and B post you can leave the doors on for constant alignment checks.
Iain MacKintosh

The bracing that Iain mentions is particularly inportant if you want to be able to move the shell about in a sill less state or perhaps turn it on its side either in a frame or on a couple of old tyres.
David Witham

Well made point David and one that I was afraid of that Dave Stille mightn't quite have grasped as he was using jacks, stands etc. He must now brace the car whilst it is in alignment so that it can be locked. The slight difficulty he may have is that when he finally lowers the car to the ground and removes the braces the gaps will move a bit, lets just hope that its not too much. For that very reason these cars should be braced before any dismantling takes place and with the whole weight of the car on its wheels.

I wonder if it would be worth if he braced his car with the door gaps just 1mm wider at the top than the bottom and the sag would correct this. It's no big deal if it doesn't because the door edge can be built up but if there is not enough of a gap you really are a bit snookered.
Iain MacKintosh

Send an email. I can help you get started with pictures and advice.
Lee Miller

This thread was discussed between 24/10/2005 and 26/10/2005

MG MGB Technical index

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