Hi guys I have read the posts on blocking the coolant bypass hole.What are the pros & cons of doing this & do most engines have this mod done these days.Also I need a new radiator for my Cooper S.What is the best radiator to add extra cooling ie. 2, 3 or 4core ? I dont want aluminium as I am trying to keep origional appearance.
Cheers

Only advantage of blocking the bypass is there is 1 less hose to blow. But they don't blow unless you use the concertina type (which S doesn't use, they run heater hose there).

If buying a new radiator I would get the UK super 2 core.
The UK 4 core is good too. May need body or shroud trimming to fit, I can't remember.

The `Cooper' UK cheap 3 core made my motor run hotter than the stock Oz one. I'd not use it on a 1275 or bigger.

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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've had mine blocked for 15+ years, no issues

Especially as originality is a concern, I suggest getting your current radiator cleaned out (tanks removed and cores cleaned) rather than buying a new one or getting it recored. If your existing radiator is too far gone, try to buy another one in good condition and have that cleaned out.

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did I tell you that I won a trophy?

So the radiators supplied by Minisport that look pretty origional are not that good as far as origionallity goes?

They are not identical to an Oz made one, no.
Oz Cooper S, Deluxe, Mini K & MiniMatic all had an Oz made 3 core radiator with 16 gills (fins)/inch in the core.
The UK Cooper one I bought some years ago for our 1293 only had 8 fins/inch. They may have changed this since.

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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 have a couple of spares down here. I think one in particular will clean up quite well if you wish.

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SooperDooperMiniCooperExpertEngineering

All garage work involves equal measures of enthusiasm, ingenuity and a fair degree of irresponsibility.

Thanks for the help Mick,I think I will go with a new radiator as the motor & associated parts are new.
Cheers