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MG MGB Technical - sills or floorpan

please help i am in the process of rebuilding my roadster and i am not sure how to proceed next,as i am replacing both sills and floorpans, the question i have is which to replace first the sills or floorpan or does it matter?? thanks in advance. also any advice on rebuilding greatfully recieved
David Hamnett

David,

I'd lean towards sills first because the floor panels lay on that structure.

Take care when drilling out the spot welds.

Are you doing this with the car in a shell state, or is the engine etc in place?
glg gimbut

If you haven't got Lyndsay Porter's 'Guide to Purchase and DIY Restoration of the MGB', republished as 'The mgb restoration Manual', then you should have.
Paul Hunt

glg, yes the car is in a shell state no engine, wings etc.
will do sills first then. thanks

Paul have got the book,the reason i was asking question is someone has welded a new floor on top of the old floor(don't ask me why, full length floorpans on both sides double thick ???)noticed when took seats out the floor sprang as new is only welded around the outer edge so a perfectly good floor has to be cut out (looks quite new as well).thanks
David Hamnett

Dave,

All I know about this was from watching my body man do the work. So, no warrantees implied!

Something he did, was to add some reinforcing on the shell to keep the structure sound before cutting out pieces.

And just a thought, refer to a good shop manual that has measurments and dimensions of the shell.

Any other thoughts out there?

good luck.

glg
glg gimbut

An interesting looking site covering this type of thing is http://www.paneldoctor.com/
Hope it helps.
Randy
1977 MGB
randy olson

Randy, an excellent site just what i needed thanks very much.can continue with mine with a little less trepidation seeing how bad that mg was
David Hamnett

If your car is quite rotted I recommend that you weld braces in the door openings and in the passenger compartment. As soon as remove the rockers and floors the car could twist and make your life even more miserable.
Mike MaGee

Don't remove the floors until you're done with the sills. Leave them there to aid in keeping the body straight - every little bit helps. If you have to do the inner sills and castle sections, cut out just enough floor to get those out. By the time you're done with the sill/rocker assemblies on a side and have a good solid section there, the floors will add a very small amount of support to the body (as opposed to BEFORE there's solid structure through the sills) and you can safely press and pry and generally manhandle them into position without fear of any body twisting.

Leave the doors on while you're doing it so you can check the door gaps and alignment throughout the process. This will indicate how things are lining up. If you've ever seen a car with body sag, indicated by closer door gaps at the top of the door than the bottom, that's what happens when you cut out the whole sill assembly. Besides the regular jackpoints used to support the work, use several bottle jacks spaced along whatever area you can, as close to the sills as you can, to adjust the body's alignment and check this with the door gap. For some reason, the above website showed them cutting out everything and leaving nothing to support the body or maintain alignment - no doors on, no supports underneath, no supports welded into the doorways, no nothing. I can only guess that they cut out everything, had the owner take his walk through the car while the car would have folded up, and then hung the door back up and did something to realign the car and supported it while they welded in the new steel. One problem with taking the door off and rehanging it is you have adjust the door to fit (whenever you do it anyway), then adjust the body to account for the sag they created, probably readjust the door, and hope the cycle of adjustments ended up making the body straight as opposed to fairly straight with a door hung to account for body misalignment. Sure is'nt how I have or will do the job. In the beginning, they say it isn't meant to be a how to guide - I think that's right.

If you cut carefully, you might be able to save the good floor.

Good luck with it, it's a big important job, but the most important prerequisites are the ability to weld, the ability to know what questions to ask ( you seem to have that!), and patience (you have an MG!).
Wade Keene

If a car was in a bad a state as shown on the above website, wouldn't a reshell be a better way to go ? If you have the time and skill to do it yourself I can see repairing it would give a lot satisfaction (I guess)! But if you are paying someone else for their time and skill, wouldn't a reshell make more sense.

Also, after having all the work done, you have to still worry about adequately rust proofing all areas, where as a new shell comes galvenised (I believe).

Has anyone been in this situation and done the maths ?

Charlie.
Charles Goozee

charles, i am doing 90% of the work myself,apart from welding and worked out how much the parts were, sills £140,2 second hand wings £80,inner wing n/s £35 (stoneleigh)dashside panel n/s £28.50 splash panels £12. rear wing halves £100.
new floorpans (if rquired as top ones are new depends on cutting ability) £95.so call it £500 as opposed to £3250 for a new shell.Also the satisfaction of knowing what i have to work with after.it will be waxoiled and fully rustproofed.
David Hamnett

David:

Interesting statement "except for the welding"! If you are going to pay for a mobile welder to stay or come around everytime you need a tack weld, this will be a very expensive project. If your welder is a mate who works by the pint it may not be too bad! A MIG welder is cheap and it will give you a lot of satisfaction to do your own welding.

The trick with this job is the project management: pick a time allotment and a job to do. Stick to that time and that job and the project WILL get done.



Pete
Pete

This thread got me to looking back at pictures I'd taken when doing the same task.
In the case of a customer's MGB (GHN3 #939), the floors were so bad that they couldn't possibly offer any support. I completely removed the floors and dressed the edges. I welded in the new floors on three sides and then removed the outer rockers and inner membrane. The inner sills only required partial replacement.

I have since made a couple of fixtures that clamp to the edge of the door opening. The fixture consists of two (2) 1.5" tubes that are RH/LH threaded so that they could be used on all the cars I worked on (MGs, Healeys & TRs). The mounting points are at the two (2) forward hinges and aft at the lockplate. The fixtures allow you to "jack" the opening (if you will) to set the correct alignment of door gaps. Lock the tubes and you're set for the job. Incidently, they are designed to allow the doors to remain in place and be closed to CONTINOUSLY check for proper alignment.

As for the MIG welding, you should try it. In a matter of hours, you could teach a nine year old to make satisfactory welds. Practise will only make you better.
Randy Forbes

Randy,
Any chance you could send or post pictures of your fixtures?

Cheers!
Rob
Rob Edwards

randy, i would also be interested in seeing a post of your fixtures,thanks

pete,yes it is a friend who is doing the welding (superb bodyman also) he is only getting a couple of beers as all the money is going on mg at moment (only kidding might get him 3 beers).
thanks for all the help everyone
David Hamnett

Sorry guys, real pictures will have to wait. The fixtures are in storage in Florida (along with half of my Healey).

I may be able to turn up pictures of them in use on a GT-6+, but I haven't come across them in a brief scan of the photo box.

Worst case, I can do a rough sketch (I'm no draftsman...) but you'll be on your own as far as dimensions go.

In all honesty, these fixtures cost me close to $300.00 to fabricate myself. As cool as they are, it's hard to justify for a one-time project.

I'm leaving tomorrow for a Z3 Fest just north of Atlanta, so if you don't hear from me for a week, don't take it personal:))
E-mail me directly to jog my memory!
Randy Forbes

David and Rob:
You have mail.
Best that I could do for now is to send you a rough sketch.
Simple tool, bolts on (no need to do any temporary welding on body for supports). Doors will close (and latch) with support fixture in place.
Works great and was well worth the effort for me.
Randy Forbes

David - must be the same person who replaced my drivers side. Apart from sealing the gap round the hole in the lower floor I have left it as there was nothing wrong with the upper floor. When the seat rails are bolted in it is to the welded nuts in the lower floor, which is welded to the cross-member so perfectly adequate.
Paul Hunt

This thread was discussed between 01/04/2003 and 09/04/2003

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