I'm POR15 ing my floor, before car gets repainted.
As I can't get into the crossmember properly to de-rust it and the floor beneath, I'm considering doing a Don Holland and breaking out the holesaw kit.
I reckon 3, 20mm holes each side on top, and maybe a couple in the back each side won't really affect its strength.
Wha do y'all reckon...??
It'll be covered in carpet anyway so uglininess is not a problem.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

i think it will be ok but what do i know lol...
im in the process of painting my floor and a couple of holes would make things easier.

matt

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i like to drive on rails

In my totally unprofessional opinion, I think it will be fine just stay close to the middle as the bends are where the strength is.

I shoulda done this too

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Yeah go crazy with the holesaw doc

You could just buy a flexible end to go on the gun...used to use them when I worked at endrust many years ago...how we used to do all the sills. Its just a piece of flexible hose with a 360 degree outward tip on the end...

Saves cutting holes...

I've considered this problem, and thought spraying it in ala Waxol etc which gets referred to a lot in the UK. However, I have no real idea at the moment. What I'd be tempted to do is cut the holes, spray inside as best I could then weld the holes back up. Since you're not spraying up onto the "ceiling" of the crossmember, it shouldn't catch fire. Failing that, find some big grommets. That way you keep the moisture out (perhaps), but can check your work at a later date. Or weld reinforcement in before you spray. In NZ, holes in the parcel shelf can be made legal by reinforcing the edge, for example.

Well, after detailing a Hyundai Elantra at work today, I noticed that have about 5 or 6 evenly spaced grommets on the underside of the sill. I think I'm going to copy this idea and put some in the mini, at least I can then inspect the things and possible rust treat if at any point it starts showing the bad signs

Woops, also, with my crossmember, it was easy beacuse I replace all my floor, so I had the crossmember all open from underneath, which did show some usefull info.
1, the top of the inside of the crossmember was indeed the healthiest part of the mini (still had factory black coating (rotodip???) in perfect condition, but the bottom corner areas it had started to deteriorate with surface rust)
2. its a piece of piss to clean and re-treat with no underside flooring
3. As a result, my floor is not level

No need for putting grommets in a crossmember, there's daylight under it already where the floor channels are.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

A Mini is 4 foot inside.
Every 4" from the top to each side (alternate, total of five each side pax/driver) surly cant do a great deal of strength lose with a 20ml hole and stray something inside. you could always sealed with covered gromet additionaly

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Stop Licking the Dog...I Don't Care Who Started It

The crossmember must give a lot of strength to the body structure (I tinkin)

Therefore, if you open up that area I would be looking at how you could brace the weakness you may have introduced

In other words, I have no eye deer

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"Show me the Mini!"

Didn't seem to bother Don Holland, he took to near every panel with ye olde holesaw...

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

I believe the crossmember gives a lot of side strength, and probably gives some rigidity against twist....

recall that the holes in the top edge of the inner guard of a post '75 (ish) clubman are there to create a crumple zone - you'd be adding the same thing to the crossmember

call me paranoid, but if I was going to do that, I'd get a nice fat washer and seam weld it around the drilled hole

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did I tell you that I won a trophy?

have Kev your doors do creak now

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Stop Licking the Dog...I Don't Care Who Started It

It's not the doors- it was the LH rear companion box, doing a Rolf Harris...
so I hit it with ye olde hammer and a block of wood.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.