I might also add, putting the original plastic/fibreglass shroud on the back of the radiator can also make a fairly big difference in how much air the fan pulls thru. I got a spare 1200 radiator with my 120Y when I bought it, and it had the shroud attached to it. Got bored on a rainy day and put it on my 1200 sedan's radiator. Started it up, and the fan sucked a s***load of grass seeds and leaves out of the radiator fins, so it really does make quite a bit of difference.

Just make sure you have good engine mounts if you install a shroud. If the engine moves quite a bit when torquing/revving you might have to make a larger shroud or replace your mounts, as they have a nasty habit of smashing fan blades and shrouds (the fan is attached to the motor so it moves where the motor moves, the shroud is attached to the radiator, and they dont move anywhere....so 2+2=...)

Spot on about crud from the block...........in the Miata (MX5) I raced I put in a low milage short block. First race fine, second one cooling issues...........sure enough crud from the block plugged a perfectly good radiator.


Tom

My big bore 1200 engine was used in my 1000 sedan for years behind a stock/original radiator & even fully loaded & towing a boat, no problem, then for a couple of years in my 1200 ute with a stock/original radiator, no problem, then back into my 1000 sedan, again without problem.

I will be using a heavy duty 1000 radiator in front of my A13 & it only got that core because the original one was rotted & had to be replaced anyway. The extra few dollars for the heavy duty core was not a concern, so I got it because I could & because I want to fit aircon later on.

For A series applications on the street, the stock size is just fine.

yeah, ive never had issues with the standard radiators before.
i guess mine just has some crud in it, but ill leave the gemmy one in for now, i dont have time at the moment to get my stock one cleaned out before my trip tomorrow.

And yet, when I got my 1200 coupe, the radiator was in a bad way, so I had it re-cored with a standard replacement.
I also cleaned out the cylinder block, replaced the t/stat, the water pump & the fan belt.
I included a cheesecloth condom type filter in the radiator, which proved a wise move, & have not had a problem since.

Even in the mid day heat of last summer, along the Hume Highway at full highway cruise speed [110k, or 68mph] the temperature actually fell slightly, compared to town driving. & it sat almost dead on the halfway mark on the gauge.

Since the vehicle needs X amount of power to move at that speed, regardless of what engine is producing it, then it would seem reasonable to assume that the same amount of heat would be produced, regardless of the engine type, capacity or form of induction.

If my stock radiator has no problem handling it, then I see no reason why a clean & fully serviceable one wouldn't handle a larger engine that was performing the same highway cruise duties.

Lets get back to the cheesecloth condom.

When my radiator was out for servicing, the crud in the block that I couldn't reach dried out, & like clay, it apparently shrinks & cracks. When the engine is returned to service, these little blocks of crud expand & shrink with the heating & cooling cycles of the engine & some break off.
At higher engine speeds they are carried into the coolant circulation stream & up into the radiator which acts as a filter to ensure that this crud doesn't return to the block.
In other words, a new radiator can be rendered unserviceable within a very short time because of this.

I was amazed at just how much crud was captured in the cheesecloth condom filter & I have washed it out three times now with very little in it the last time I did it.

A partially blocked radiator will handle the low heat output at low speeds, but may not have the reserve capacity to handle the higher heat output at higher speeds.
Have a good look inside the 1200 radiator & see if you can see any crud in the few tubes that are able to be viewed. Reverse flush it if you see anything at all.
No point in wasting a perfectly good radiator if you can clean it out.

id keep the gemmi one if possible, you will appreciate it in summer for sure.

Quote:
yeah had a brand newwy.
but the rest of you were spot on. went out to 120fly's and he had a spare gemmy radiator there. it worked a treat, temps dont go over halfway on the guage now.
ill get a new one made when i get back off my holidays.

I will back up what Freak and 1200GXman said, with astock A12 newly rebuilt engine and new radiator, as soon as we went above 4000 RPM's the car ran hot...............just shy of the hot mark. Even in bumper to bumper traffic with 110 dergree Vegas heat it was fine............get on the freeway and within 1/4 mile the temp would spike. Intially we used a B210 / 120Y radiator and that helped...........the 3 core GX radiator solved it for good. Even at the track when it's 106+ and me buzzzing the engine to 8K it still stays between 180-200 degrees.

Tom

Is this the twin carb A series motor that you have had for ages? Quick question. Did you replace the thermostat after it had been sitting for so long? Forgive my ignorance but I can not remember having read anything on your engine build up.

Bigger or tripple cored radiator is the only solution. The higher revs generate more heat and the increased airflow is too fast for efficiency. All the 1200s ive had standard or modified run hot on the highway with standard radiators.