BIW differences in the engine room

[lagolag]

Hi,
I'm new to the group and I'm waiting to take delivery of a 230SL 1967 in june -21, luckily I have my SL55 to drive while waiting.
But while waiting I have watched lots of pictures and I notice that there are differences in the side walls of the engine bay,
some have holes and it seems as if they occurred in the end of 1966 as I've seen 250SL without it but it's strange as
I've also seen 280SL without these holes and that puzzles me more as 280SL production started in the end of 1967.
If anyone can give a good explanation, I would be grateful, just curious.
Thanks,
Regards Lars

[doitwright]

My understanding is that the holes were put in to allow air to escape when the chassis was dipped during production. According to a restoration done by MotoringInvestments.com the holes originally had rubber plugs and would have been installed prior the car being painted. In mist cases, the plugs eventually deteriorated from engine heat and fell out.

[doitwright]

Photo Taken from http://historic.motoringinvestments.com/MainPage.htm

[Pawel66]

On the pages of Motoring Investments there are pictures of this "Holy Grail" - the preserved 280SL. On those pictures these plugs have remains of the body paint on them (the paint is falling off the plugs over time, as it does not stick to rubber as well as to chassis). I take it the plugs were painted body color, which was confirmed, if I remember correctly, by several Members.

[neelyrc]

Lars, you mention specifically the holes and plugs in a 280SL in your original post. 

Attaching are a couple of pictures of the area under discussion on my factory original 280SL, Chassis 007749, January, 1969, build.

The plugs shown are original from the factory and as can be seen they retain the original factory paint in body color.  Please note the plugs on my car are plain without any inscription and thus differ from those in the photo attached to Post #2 above.       

[Pawel66]

Indeed, the plugs you can get from MB today for those spots have the inscriptions. They are "universal" plugs that go in many paces in the car.

[teahead]

so to be correct, the plugs should be painted body color?

[neelyrc]

Yes. At least in January 1969 they were definitely painted body color.

[lagolag]

Thank you all for your answers! 
The question remains from when this change was introduced in production, we know for example when the floor in the trunkwas changed 09/1964 and the fixations for 3-point belts were introduced 03/1966. We know that 250SL started to be produced 11/1966 (6 pieces) and 280SL 11/1967 (7 pieces) all according to available statistics. The picture I have in my initial question is from the car I bought and it should be built 11/1966 based on VIN. 
It should therefore be extremely rare with 250SL without holes and completely impossible to find a 280SL without holes, if the holes in the pictures are plugged, it should be as visible as the spot welds on the wings.

Regards Lars

[mbzse]

This has been thoroughly discussed. Is it not in the Tech Manual(?)

Anyway, the holes and their plugs were introduced on the 280SL bodywork at chassis No 5620, beginning of October 1968.
The rubber plugs were painted over with the car's body colour at factory.

A tech change document was issued from the Factory with instructions for drilling the holes on cars already delivered, see attached. This was to be done at the Dealerships.
These cars then were fitted with plugs that were _not_painted.

Some info on _why_ the holes were introduced in this old posting:
https://www.sl113.org/forums/index.php?topic=15001.msg103029#msg103029

[Pawel66]

Thanks Hans!

I have not seen those posts.

[lagolag]

Thanks Hans!

That explains it all.

Regards Lars

[Cees Klumper]

Forgive my ignorance, but what does 'BIW' mean, in the name of this thread? ("BIW differences in the engine room"). Doesn't seem to be a typo.

[lagolag]

BIW is the industri term for Boddy In White - the metall boddy.

[Shvegel]

Well, to make it even more confusing the later 1970 and 1971 cars had the holes but not the plugs.

[MikeSimon]

My car, 22774, December 1970 production has the holes and no plugs. Whether they have never been in there or were lost over the years, I don't know.
But...why in the hell did the factory issue a bulletin to drill the holes in cars that were already delivered, if the holes were intended to allow air to escape during "dipping"....??

[Shvegel]

I have a few pictures of very original cars that shows the holes but no plugs.

I think the thought process went something like this:

The front reinforcements are corroding.

Drill holes so they dry out inside.

Dip chassis in primer to keep rust at bay.  Problem solved! (Bwahahah).

Dirt is splashing out of the holes when you hit a puddle.  Plug holes!

Umm, it looks like the primer isn't working quite as well as we hoped it would.

Remove the plugs to let the reinforcements dry out.

I studied the "Holy Grail" rather extensively early on not realizing how many things changed during the run of the Pagoda so I had my painter install the plugs and paint the car so the proper rings of primer were around the holes.  Well, I later realized the plugs were not supposed to be there and had to repaint my engine compartment to cover up the very rings of primer I paid someone to make. Oddly enough it looks like the lower frame area does indeed still have plugs even on the latest cars.

Judging by the funky vacuum switch by the battery and the metal coolant bottle I am guessing this is a very late car.