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Hello all.Can anyone say what time slot rigid foam was injected into mk1 sills?Thanks.

From some time around mid 1960, I think, starting with Austin 7 body number 41416, Countryman 2203. I'm not sure when it ended, perhaps whenever they re-designed the sills?

Tim

That’s an interesting question. I didn’t know about filling the sills with foam by the factory.
I have spotted foam in the sills up to the A posts of my August 1960 Morris Mini and thought that was something done by a later owner.
Does that mean I should keep the foam once I‘m starting the restoration?

Regards Daniel

Foam filling was done by the factory for a period, but I think they also instructed the dealers to 'retrofit' foam to earlier cars that missed out, as part of the additional body sealing that they realised was needed after the Mini was released.

You hear two versions of whether it was effective or not. 1) The factory bought back some old vehicles several years later and discovered that the foam had perfectly protected the inside of the sills and 2) It was a dreadful water trap and the sills rusted even faster with the foam in there.

Tim

There is a bit of information here about foamed sills.

https://mk1-performance-conversions.co. ... randa.html

Generally speaking factory fitted foam worked well to protect the sills, but could create a water trap above the foam. This however wasn't the primary reason it was used. It was used to stop water getting through the badly designed floor & filling the inside of the car with filthy water. In certain conditions condensation could get trapped in the panels above the foam & this is where the rot took place.

When restoring a car with foamed sills there are a couple of good reasons as to why you should remove it;

1) The foam when burned is highly flammable & gives off toxic fumes, neither are good when you are welding.

2) Mini's nowadays rarely see wet weather so a good coat of cavity wax once the repairs are complete will do as good if not a better job in protecting the insides of the body that the foam ever did.

If you do want to retain the origianl foam or something like it. Thoroughly WAX The panel cavities before injecting foam, but make sure your welding is excellent & you don't over do it. I have seen badly injected foam blow newly welded sills right off a car!

The water leaks/rigid foam in sills and the foam welding repair precautions for Dealers are pointed out with diagrams (1st Feb 1961),
See page 13 here:-
https://mk1-performance-conversions.co. ... ni-pt4.pdf

ekjken wrote: ↑Tue Jun 20, 2023 8:40 pm Hello all.Can anyone say what time slot rigid foam was injected into mk1 sills?Thanks.

They started in early October 1960 @ Longbridge.

mk1 wrote: ↑Thu Jun 22, 2023 9:21 am
2) Mini's nowadays rarely see wet weather so a good coat of cavity wax once the repairs are complete will do as good if not a better job in protecting the insides of the body that the foam ever did.

Thanks for clarification, Mark‘s second way is what I also thought about the foam. I will do it that way once I‘m starting with the bodywork.

Thanks very much to all who replied to my question on rigid foam in sills.

mab01uk wrote: ↑Thu Jun 22, 2023 9:30 am The water leaks/rigid foam in sills and the foam welding repair precautions for Dealers are pointed out with diagrams (1st Feb 1961),
See page 13 here:-
https://mk1-performance-conversions.co. ... ni-pt4.pdf

That's an invalid link.

winabbey wrote: ↑Fri Jun 30, 2023 4:18 am

mab01uk wrote: ↑Thu Jun 22, 2023 9:30 am The water leaks/rigid foam in sills and the foam welding repair precautions for Dealers are pointed out with diagrams (1st Feb 1961),
See page 13 here:-
https://mk1-performance-conversions.co. ... ni-pt4.pdf

That's an invalid link.

The link was still valid when I posted it....the link was to a colour page of a BMC document for 1959-61 Minis for BMC Dealers regarding safety when welding sills with rigid foam. I sent a scan of the original documents some years ago to the Mk1 site but it looks like it has now been deleted or moved by Mark during his recent reorganisations of the the Mk1 Performance website?

Here is my scan of page 13 on Rigid Foam:-

It was also reckoned that foam injection increased body rigidity by 8%.

I think I read that in either a Vizard book/article or the Marshall/Fraser Mini book.

Certainly the 59-60 cars were remarkably rot resistant compared to later ones. I only had one 1959 shell - 618AOG - and that was perfect when I had it in 1986/7. It had the mud shields under the front wings to protect the A panels. I bare metalled it before painting it and every panel was original.

The naughty young rascals round these parts are using that expanding foam stuff to fill the speed camera boxes. Apparently it increases the rigidity of the box part so much, that they pop the sides. Maybe they are doing it to protect the boxes but, sadly, the expanding foam knackers the cameras and other electronic stuff inside too.

I think I saw just such an exploded example on the way to Cirencester last week. They really need a jolly good spanking...... as do the scoundrels filling them up!

The fact the foam was added later in 1960 explains why my April 60 had no foam. I thought they all had foam so was surprised when none was found. My flat sills are good with just one patch required.

As Peter says, the 'risk' with injecting foam is that it can destroy the structure, if too much is added.
The trick is to add a little at a time, and let it do its thing.... (Ideally with the hollow section 'standing up' so it fills completely)

The foam used these days is polyurethane; available from Glass-Fibre suppliers as 2 liquids which are mixed together (don't get it on your skin..!!).

The advantages are:
it absorbs a certain amount of moisture during its curing;
sticks like s**t to a blanket (as the saying goes...);
and is 'closed-cell' so can't absorb liquids after curing...

But as Mark says, it's not really necessary these days..