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MG Midget and Sprite Technical - Body Tub Modifications

I am interested in hearing what body tub modifications and tricks other may have used which improve or enhance durability - keep rust at bay etc. The sort of little tweaks that can be done when repairing a tub and before the paint stage. I am not meaning modifications for fitting different engines / gearboxes.

As a starter these are some things that I have done:

Drill a 5/8" drain hole in the outer sill top directly beneath the A post hinges. It allows any water that gets into the hinge box to drain away into the sill.

Drill a number of extra drain holes along the bottom edges of the sills! Drill extra drain holes in the bottom of doors (wind-up window ones)

Fill the narrow cavity between the boot floor and rear wings up to the level of the floor with resin and seal off with seam sealer (sq bodied Sprite)

Same treatment for the triangular cavities at the back of the rear wings and across the down-turned joint between the rear floor and rear valance. All brought up to a level with the floor so there are no water traps that don't dry out.

Weld a 30mm wide strip around the lower rear edge of the rear inner arches - it acts as a drip rail so that water and mud is shed off rather than blasted up under the rear floor.

any oher ideas / modifications worth considering?

Guy
Guy Weller

I'd beef up the ARB mounts as well.
Brad
B Richards

ineffective breather ensures liberal automatic oil coating ;)
robnrrugby

I'd weld a couple of plates each side to fill in the triangular sections between the front wheel arch and engine compartment; cracks appear in these (in my case due to heavy braking loads with improved brakes and sticky tyres. See pic. I think many racers do this as part of chassis prep.

(I'm refraining from crack refs here' we've been through them already.)

Also - I noticed on mine that the horiz bulkhead joint has opened up - possibly due to my shortened tray.

A


Anthony Cutler

Interesting modifications Guy.

I'm in the process of rebuilding the back end of my midget and all those flanges and small gaps between metal, eg. wheel arch to outer wing, seem insane to me. I've always thought that BMC/BL must have had a special design team thinking of ways to build IN rust traps.

Be good to see a few pics of your mods (where you can fit a camera lol).

John

J Marklew

Thanks,
Brad - I had forgotten about ARB mounts - I did those as well.
Ant - I have just replaced the triangular webs on the tub I am doing. Although this one is only for road use they do seem very flimsy and I had wondered about welding a box section tube inside the sloping upper section. Or is yours strengthened horizontally, parallel to the main chassis legs?

I do wonder at the lightness of the A frame fulcrum point brackets - I have had these crack before.

Any other ideas?
Guy Weller

I know someone who has drilled holes in the bottom of their sills, but has welded small lengths of pipes to these, pointed back and angled away from the elements.

It acts as a redimentary 'non return' valve, letting water out but stopping water splash up and ingress into the sill holes.

Same with floorpans; someone I know with an MGB has put holes in the footwells and then plates over these underneath, welding front, left and right, but with a gap at the back, which let the water drain out 'backwards' but stop splashes pushing their way in.

Not sure how general we're being, but I would personally:

- Change the bonnet hinges to be 'quick release'
- Strengthen the front suspension area
- Strenghten the ARB area
- Weld and seal off all chassis rail gaps, especially at the front
- Remove the 'lips' at the bottom edges of each front and back panel (make it a curled over lovely 'rounded' edge, not sharp flange of steel) so crap doesn't get caught there and the flanges don't rust!
- Modify the radiator mounts so it can be 'slotted' in and out.

Mainly though, I'd really like a I'm-pipe-dreaming removable section of the gearbox bellhousing so the clutch can be worked on without engine out!
Rich Amos (1 Sprite 1 Midget!)

Rich,
I have done the rad mod - mine now takes out by undoing two nuts, which are on welded in studs so there is no fiddling about.

I have toyed with the last idea - well not a removable bell housing panel, but a removable gearbox without disturbing the engine. With a 5 -speed using a removable cross member/ gearbox mount I reckon one is half way there. Shorten the under-tunnel floor (or retain a bolt-out section for strength) and one should be able to drop the gearbox out by just removing the prop shaft. Its just awkward getting at those bell housing bolts.

Guy
Guy Weller

How about enlarging the clutch slave access / back-of-hand-lacerating aperture in the driver's footwell? It was a "delete option" on my heritage shell so I had to cut it from scratch anyway - so I made it a sensible size. Then I fabricated a matching cover from some scrap sheet steel - old mouse mat glued on one side to seal it, padded matching trim vinyl on the other, screwed into place.
Gearbox filler access hole could benefit from similar treatment?
Steve Clark

There may be ways of modifying the bellhousing/ear engine plate to feature captive nuts or something similar to ease removing the bolts. It's one of those things I'm sure many have thought about but non brave enough to try!
Rich Amos (1 Sprite 1 Midget!)

On my Frog:
Triangular gussets behind the front suspension into box sections (with same access hole, stronger and crud can't get in.
Sill finishers reversed so they are a box not a double skin, same to rear wing/ inner wings (on the Frog)
Drain holes in sills with covers similar to those mentioned above.
Just about everything seam welded.
Rear wings behind wheels box section again rather than the double skin.

This is all uppermost in my mind at the moment as repairing the Mk IV clutch release highlighted the need for a reshell (don't ask), I wheeled my spare shell into daylight today to consider what needs replacing to use it, I'll be pinching any more good ideas.

I read somewhere that Frontline raise the door gap part of the sill 2" with 3mm plate to add some strength, I'll probably do that on the reshell.
Paul (MkI

I have in my shed a '74 that has done 108,000 miles. It has been rust proofed at various times and drowned in oil, and is quite rust free. In this case, maintenance of drain holes and regular cleaning out of crud has ensured the shell survived. I don't know what underbody coating was used but it is white and still very soft, and still very much attached to the steel, unlike the tar coatings that were often used. They became hard and brittle and trapped moisture underneath.
On the '73 I am building I painted the inside of the sills, pillars and skins before assembly, and closed all the small gaps where panels intersect. The sills are sealed up so water can't get in from the A&B pillars. I tried ensure that water can't get inside the A pillar but if it does it drains out onto the top of the sill under the door. It has been seam sealed everywhere before painting, and since painting it went back on the rotisserie to be flooded in thinned waxoil before having waxoil sprayed through all the cavities. It was messy and took quite a bit of cleaning up afterwards but I'm confident(ish) that all surfaces are coated and moisture cannot reach steel even in the joints. The traps in the rear quarters I've left open so that if they ever get wet they can get dry again. I intend fixing the seat runners to the floor with the carpet cut around them so that the carpets can easily be removed if/when they get wet. I'll also now modify the radiator mounting so removal is an easy job (thanks Rich, Guy).
The race car has been seam welded and there is no static flex in the body. The roll cage helps with the stiffening also. Some racing spridgets have had square tube inserted and welded inside the chassis legs and this has stiffened up the front even more. No stress fractures evident yet.
Mike Allen

Hi again.

See the chassis mods by Jonathan Smith - raised sills in particular - for his KMidget.

A


Anthony Cutler

Mike,
Interesting, your approach is slightly different regarding the sills, A and B post. I assume that water will get in and add extra means of it draining out. You make sure it doesn't get in in the first place. I wasn't really listing seam sealer but I think a thick sealer really is your friend. It not only covers seams, but can be moulded shaped and smoothed into all those little cavities to encourage water to run out, rather than get held in with all the road crud that gets blasted at the cars. I also think that (at least in the UK climate) a major problem is condensation on the inside surfaces of the car as temperatures drop in the evening. The inside of the rear wheel arches being an obvious area where condensation forms and then runs down into the narrowing gap where inner and outer wheel arches meet at the lip above the rear wheel. Difficult to do much about this other than use of plenty and repeated applications of waxoyl sprayed forward of the boot sides.

But I have strayed "off topic" on my own thread! This was meant to be about body tub modifications, not about anti-rust treatments!

Guy
Guy Weller



Guy,
I cut a 5" hole in the boot floor exactly over the sender unit so I don't have to drop the tank to service the s.u. Also lets me check the top of the tank for rust. Thin sheet of m.s. with "mouse-mat" gasket to cover it .
Arthur Jessop

Arthur, Now that's a good one I hadn't thought of doing! At the moment my Frog has so much rust in the boot floor it doesn't need an access hole cutting! But when I weld the new floor in I will be doing that modification!

Guy
Guy Weller

Guy, have you become Guy MkI,MkIV? Is there something in the air round here? Excellent news.

If it's a Frog shell the wheel arch double skin can be avoided to some extent by tweaking the inner wing so the lip is reversed then seam weld as a box section, that was what I did to my Frog shell. Can't do this with the later square arches due to fat tyre contact issues, not sure if it would work with the later round arch.
Paul (MkI

Could be, Paul. Although I think strictly speaking there is no such thing as either a MK1 Sprite (they were just Sprites) and my blue car isn't actually a MK IV, like yours it is just an Austin Sprite.

I think I understand what you mean by reversing the inner wing lip, but don't quite see how that then makes a box section. I do like the idea of reversing the sill fillers - only I have already welded the near-side ones on in the normal way!

Guy
Guy Weller

This thread was discussed between 23/10/2008 and 24/10/2008

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