Since I blew the welch plug out of the LS's motor and replaced it, the radiator is holding a lot of pressure, after even a short run and even after it has cooled down. It blows a lot of excess water (more than normal) out of the over flow hose when hot in to the catch bottle I have set up ..

Could it be a air block in the system or could it be the radiator itself?

I would like to put a bigger radiator in so can anyone suggest what sort I could use or would it be better to get a new one built?

Remember, it's an LS with the thermo housing facing backwards and the over flow pipe down the side...

I'm more-or-less replying to this as a bump for you... and to start some discussion

There's nothing inadequate about a standard mini cooling system - as long as everything is up to spec, the standard system will cope with all climates and needs... they raced at bathurst with the standard cooling system... only the biggest baddest fire breathing engines need anything extra

Blowing a welsh plug out of the motor is a symptom, not a cause. I reckon you could put the biggest radiator imaginable in, and it'd still misbehave.

what sort of temperature does the car run normally?
what's the condition of your thermostat, water pump and the radiator itself?
does the car run OK? could it have popped a head gasket into the water jacket?

whenever I have a radiator out of a car, I run water through the engine and heater from the garden hose, clamp the nozzle into the top hose with the thermostat removed and run the water out the bottom hose till it is clean, then do it in reverse, same thing with the radiator when it's out of the car, fill it with water and shake it like mad, flush it both ways... I regularly get radiators disassembled and cleaned out as well

(however, I've seen pictures of clubmans on here with radiators running right across the front of the car, out of a mazda 323 or something - measure it up and search the wreckers)

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did I tell you that I won a trophy?

Hi skssgn...

what sort of temperature does the car run normally?
82C is the normal temp it runs at..

what's the condition of your thermostat, water pump and the radiator itself?
Thermostat is brand new three weeks ago, water pump and reco radiator put in when the motor was rebuilt 4000k's ago..

does the car run OK?
Yep, no problems there, runs like a top.

Just was wondering why the system stays pressurised tho??

If it's holding lots more pressure than it should (and it sounds like it is) then I'd agree with skssgn -- sounds like you might have a head gasket leak into the water jacket.

If the motor is newly rebuilt that might make sense too, as you'll only just have fitted the head gasket If that's the case, has it been retorqued since it was fitted? Maybe do that, it might nip the gasket up just enough to seal.

All conjecture, of course...

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Simon

The adventures of an owner builder in the Tallarook Ranges

make sure it has the right radiator cap, as there are different pressure ratings.

a standard jobbie should be fine on a smallblock, but you could fit a 2-core which is what i am running on mine which i recommend.

There are different length radiator necks, most Oz radiators are long and the UK ones short. Don't mix em up...
Last time I saw this problem it was on a member's car at Wakefield Pk, it blew a welch plug, then 2 radiator hoses on the way home before we sussed that the cap was too long and not relieving under pressure as the water expanded.

re the 2 core vs 3- a reconditioned Oz 3 core (all 16 fins/inch from 1965 on) rad cools my 1360 as well or better than the UK 2 core.
Forget the cheapo UK 3 core, it doesn't have enough fins... and they are made flimsy- the side shrouds fall off the tanks.
Mine is a wall ornament now.

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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.

agreed, same here, the side shroud fell off and it couldnt cool my engine before it was supercharged.