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MG MGB Technical - Webasto - hole location?

Folks, I'm approaching the critical moment, following bare-metal stripping etc. on our 73 BGT,where we enlarge a pre-existing hole in the roof and fit a new Webasto sunroof. Couldn't find much in the archives, so could anyone clarify for me, specific to the BGT, what is the optimal distance from the front seam or a suitable datum point, for the front edge of the hole to be measured? I've read of the need to ensure sunvisors open up freely - presumably meaning " don't cut the webasto hole too far forward"? - but any advice will be greatly appreciated. With thanks, John Hall.
J.P. Hall

John, a couple of photos which may help. The Webasto is a 34" x 34" and was fitted by the MG dealer when the car was first sold. The first pic shows inside the car and its position relative to the sun visors - there's about 3mm clearance between the visors and the Webasto deflector fittings. The second pic shows the distance from the front of the roof. The datum point I have used is the front crease in the roof panel (highlighted here in chinagraph pencil). The distance of 254mm is from the crease to the inside edge of the Webasto aluminium edging.

Brian Shaw

Second photo

Brian Shaw

B- Very classy looking ride. Vic

vem myers

Brian - thanks very much for the prompt response; wow, you have a massive deflector! - the deflector which came with mine( from R.S.Coachbuilt in London) is a set of skinny little bits of darkened perspex - probably less intrusive, but I hope it works! Not that I have any hair to blow around. One point from your photo (interior) - I wonder whether the aluminium trim finishes at or near the actual hole, at the front - what do you think? John.

Oh and vem (is it Vic?) - what is the significance of two ladies in a conversation on a lounge? I must be missing something! JPH.
J.P. Hall

John - I'll take a closer look at that tomorrow and hopefully post more info. I would guess the trim fixing screws you can see in the photo go through the roof panel and into the (wooden?) Webasto frame.
Brian Shaw

I just removed a few screws and lifted the trim. The roof panel cutout is 3 to 4mm inside the trim where I took the measurement from, so that makes it 250 to 251mm back from the roof panel crease. The deflector is smoked grey Perspex 200mm wide x 5mm thick.
Brian Shaw

Brian, you couldn't have been more helpful - thanks very much mate! Please put your car back together now, as I promise not to ask for any more detail! Because we're working with a pre-existing hole, you've helped me figure out how far from the front edge to try to locate the Webasto framework; we'll offer up the sunvisors to see how it all fits, but my feeling is that we'll just make it. Worst case scenario, we fit the Webasto and then have the visors made slightly narrower - wouldn't be a problem.

PS - noting that you are in Chester, can I mention that my (elderly) father and I will be visiting Shrewsbury for a few days in April; I've been contacted by a fellow MG enthusiast ( Martin Williamson) in Chester re. possibly hiring an MG6. Perhaps a beer and sandwich some time?? Regards, John Hall.
J.P. Hall

Hi John
Just caught your post.
I have two GTs (one a V8) and both are original UK cars each with a Webasto sunroof. Whilst the V8 is completed I have been able to measure the hole dimensions and it's relative location of the other car which I'm currently restoring.
The actual cut out is 775mm x 775mm with the front of the opening 235mm back from the lip that sits above the windscreen opening and the rear 155mm in from the fold around the tailgate opening.
The V8 appears to have similar dimensions although I haven't undone any of the perimeter fittings.
FWIW I wouldn't bother with the wind deflector - my car is perfectly comfortable at any (read "high") speed.
Peter Malkin

Gooday Peter - thanks for your help; I like the sound of 235mm if that is from the front crease line as described by Brian in his message. I'll be checking mine on Wed. Morning, and will let you know my findings! John.
J.P. Hall

This thread was discussed between 06/01/2012 and 08/01/2012

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