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GT6 MK3 Sill alignment

Alex Lowe

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Hi all 

Having trouble with the fitment of my new outer sills the top seems to be too far inwards leaving a lip where it meets the door. This was not present during test fitting as now i have welded the previous parts in place being lower a post, inner sill and strengthener. 

So now im at a bit of a loss as to how best to correct this one.


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On 12/09/2020 at 22:58, Brooky said:

Alex  so if you pull the sill top towards you so the outer is then flush with the door where you want it  how much of a gap is there between the top lip of outer sill and inner/strengthener lip?

Hi Brooky there is a gap of about 2/3mm when pulled out to the desired position. 

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I  expected sills  just to fit like a nut on a bolt with the correct thread.

They don’t.

I can’t explain why, but they don’t.

It seems they often need a quite large degree of adjustment -and added metal.

The sill may well need expanding outwards by  cutting and inserting a fillet of metal:

- and the relationship floor/sill isn’t always straightforward as the replacement floor flange can vary in depth and depending on this there may be a variation in sill flange/floor flange as per diag.

-Just  replacing the parts “as is” and keeping everything wonderfully braced may be fine - but very likely there will result the commonly seen “lower door edge step-out”

Take your time ...and  Good  Luck!




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Most difficult!

At risk of getting banned form the Forum for repeating myself I still want to say that the various aspects of panel fit/alignment on Spit/GT6 are not to be viewed in isolation: Everything from the valances back to the B-post has to be 'worked in' together. The only reliable datum points are the outer corners of the scuttle  and their relation to the upper, outer, corners of the bonnet (right height together, 5/32 to 3/16th inch gap).

But down to the specifics of your issue:

I'd want to check two things next (following on from Alex, previous post)

a) How does the lower (rear) edge of he door sit in relation to the forward extension ('foot') or the rear wing? If this is a nice fit then that acts as a reference point. But if that also is 2 - 3mm inward then that will need to be corrected before fitting the sill.

b) Does the door follow a nice line with the trailing edge of the bonnet? And, if so, is the rear edge of the door in a nice line with the forward edge of the wing. With the available adjustment on the doorside hinge plates it may be worth playing with these lines to see of any of the 2 -3 mm can be taken up with slight rotation of the door.

If every other aspect is good then the likely issue is how well the sill is made and it is commonly reported that repro sills are pressed too skinny in the middle section under the door. So it then becomes a case of getting extra width in the tread plate part of the sill. Easy to say, less easy to  achieve elegantly. Three ways that I can think of:

a) Simple and brutal: Slice along the length and re-weld. As previous post above. Simple but risks a lot of disortion.

b) More elegant and adjustable: Slice off the lip and make an entirely new lip section from 1.0mm steel with a joddled edge. Weld the lip section in position then position of sill can be finalised by sliding in and out over the joddled face. Then weld.

c) Panel beating; If the lip has enough upstand it may be possible to move 90 degree fold by beating over a heavy rectangular steel bar. But gaining 3 mm width would mean sacrificing 3mm in height of the lip. More tricky and requires more equipment.

If, even with all the best efforts it doesn’t come up quite right all is not lost. It’s not too hard to ‘bulk up’ the top edge of the sill with a tough, hard setting, filler. While not to be recommended as first port of call, filler can add an extra couple of mm of improvement in pursuit of the best appearance realistically possible. By ‘tough /hard’I mean a metalised filler e.g. Alusoft.

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Chris - I was considering 're-profiling' the sill near the rear of the driver's door where the shut lines are the worst. Before I do, I intend to try adjusting the door to get a better fit as I have noticed some interesting 'packing' under the hinges. I want to get the fit as best I can before stripping the paint etc. and adding re-profiling. The annoying point is that the fit is fairly good up to a point about half way along the door. This confirms the theories about the sill even though it was fitted 30 years ago there is no guarantee that the pressing was any better then, than now.

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