sills - advice please..

[tim-d]

Folks - have decided my diy welding not up to scratch so am shortly going to have my efforts ripped off and professionally redone - have put front floor repair panels both inside and underneath - floor now effectively triple skinned but its the sills I'm not happy with - have doubled both inner sills - all relatively easy but the new outers that were pattern panels from moss fit well but it's just my capability and finishing letting it down - going to supply some heritage panels for it this time all well coated in several layers of hammerite inside - however in conversation t'other day was advised that when completely moisture free to fill sills with expanding foam of the building variety - on face value this seems like a good plan - messy and must ensure totally filled to eradicate any moisture traps - but anyone care to offer an opinion as to the pro's & cons of doing this? surely given propensity of mini's to rot mfr would have done this if there was a benefit in it? the only cons I can come up with is that moisture will eventually get in through the sill vents and the mess!

[Dino42]

tim-d said:

surely given propensity of mini's to rot mfr would have done this if there was a benefit in it?

They did !
The original '59 mk1 had foam filled sills, they stopped doing it after a year or so - presumably cost cutting?

You could certainly try it, but make sure you use closed cell foam, if it is open cell and therefore absorbs water, you'll be in a worse state.
Also foam filled sills are a real pain to repair.
Personally I'd be more worried about the multilayer panels, that'll surely encourage rot.
I'd just plaster the rect in Waxoil.

[Skyedriver]

And when you weld them on the paint burns off anyway

[GHW]

Firstly, triple-skinning the floor is a big no-no. The rotten panel you've covered up will only keep on rotting and spread the rust to the two new panels, so in 18 months you'll just have to rip it all out and do it all over again.

As for the sills - they're there to let water (condensation) drain from the rest of the car - so if you block them up you'll create water traps above them. Best to put new sills on, then thoroughly rustproof the insides with dinitrol or waxoyl (no point rustproofing before welding because it'll all burn off), then finally make sure all the drain holes are unblocked.

[cooperman]

If you do decide to faom fill and use that expanding stuff, make sure that you drill lots of expansion holes in the inner sills or the expansion can split the welds. I know a guy who did that on a Triumph 2000 and he had a real problem as he had to do the whole jonb again and very nasty fumes and vapours came off when he cut the stretched and damaged ones off the car.
By the way, the reason the foam filled sills were only on the '59 cars is exactly that. A bodyshop guy was taken to hospital after fumes from welding that area (gas in those days) overcame him and he was hospitalised.

[love machine]

I have one in the garage with foam filled sills with no rust. I think they used to do it right. Nearly every 59/60 I have seen has good sills (foam filled)