Hi folks,

Brought my 1988 round nose Mini over from the UK a few years ago when I emigrated… Re-building the engine at the moment and wondered what size oil cooler/ radiator I would need to keep a 1380 engine cool?

I have a 4 core radiator and a 10 row oil cooler, both of which worked OK in the UK on a hot summer day (yes there is the odd hot day in the UK! )

Question is; is this enough for a hot day here in Melbourne? If not what more will I need?

I am sure you will get many a reply to say a oil cooler is not necessary, unless you have track time planned.

Run what you have, it'll work fine.
But as junior said a cooler isn't really needed for road work, if you are running decent 20W/50 oil. Mine is now on the shelf. I get the same pressure (70psi) with or without it.
I use KMart's KMX 20W/50(used to use Castrol Edge Sport 25W/50).

But beware, some well known oils (eg GTX) need a cooler to stop pressure going south on the freeway.

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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.

4 core and 10 row sounds good.

imo oil cooler is a must have.

Thanks folks, wouldn't want to fry the engine after rebuilding! Will run with what I have got.

I agree a cooler is essential, not just to maintain oil pressure but to make sure the gearbox lasts, The plastic bearing carriers for first and third motion shafts go brittle and collapse if they get too hot, temp is about 95 degrees from memory. Had this happen to me so always run a cooler with oilstat since then...

IMO it's mainly dirty, acidic oil that buggers the bearings' plastic cages, not the temperature.
The plastic cages have been around for a while, I've never had a problem with them but I do change the oil every 1500 miles. Religiously.

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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.

to determin IF a cooler is required, install a temp guage in the gearbox below the oil level and drive around on a hot day. I think you will be surprised . the oil removes quite a lot of the heat from the block and this is transfered to the gear box.

As for the "plastic" cages in the new bearings go to NTN [they manufacture all the RHP brgs] and Torrington websites and read up about the peramiters and conditions for the use of plastic cage bearings. MAXIMUM temp 120 deg C.[ at this temp the plastic starts to deform] continuous operating temp 105 deg C. the plastic compound used is chemical and hydrocarbon resistant, but definately is not heat resistant.

The biggest factor with the plastic deteriation is the hot oil impregnation of the plastic surface and the continual heating/cooling of the plastic. this causes it to become brittle over a period of time. I have seen plastic caged bearings that have done bugger all work that have cracked.

If you do run a cooler, I would, then set it up with a thermostatic control valve that diverts thru cooler once oil temp has reached 60 deg c.

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Research is the difference between speculation and investment. Anyone who copys some one else will always be second
www.minisprintgt.com

I don't think an oil cooler is a must. However, Cooper S's had them standard so when I built my car I thought why not?

I use a Serck 13 row cooler just like everyone else. Make sure you get the braided hose though! Why? Not because they perform any better but they sure do look cool!

On a side note, I recently picked up a 1275 motor that had one of the old MK1 S oil cooler setups which is a 9 row I think mounted sideways above the oil cooler with small steel tubes similar to the standard Mini hooking them up, very odd indeed. I'll give that a try sometime and see if they perform any different. Probably not but would be interesting anyways.

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1964 Morris 850, 1330 Supercharged - 81.8hp atws.
1975 Leyland Mini S 1100S powered - Nice and reliable.
1977 Leyland Mini LS - Project LS-T

I did the oil temp test with a spare gauge and a dipstick probe temp sender. It clearly showed how good the alloy sump is as an oil cooler, especially when the hailstorm hit!
The water temp was still up high and the oil temp was not reading.

some of the largest bearings in the gearbox, such as the AAU1365 double roller, have non-metallic retainers. I have used and bought RHP bearings for this Rover part number. While searching the web, I came up with this table on this RHP webpage.

http://www.ahrinternational.com/retainer_materials.htm

Without knowing exactly which non-metallic material is used for the retainer,
most of the materials listed in the table have very high temperatures listed. It doesn't say so, but I would imagine that these temps specified are to be interpreted as maximum temperatures.

I have seen oil temps as high as 250 F without any apparent retainer damage.

Has anyone observed heat damage to non-metallic bearing retainers removed from Mini gearboxes ?

There are only 2 ways these non-metallic retainers (cages) present, I find:
1. Intact, or-
2. In little bits spread all over the box and all the balls in the bearing sitting in a semicircle around the bottom of the race.

I find the broken cages are usually all black and grotty looking, to match the crappy oil they ran in.

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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.