Over 20 years ago I had a 71 sedan with a 4spd. My brother-in-law worked at a Datsun dealer and owned the car before me. He drove it for a long time when I bought it. He had replaced the rings and done a valve job on it in the past. He told me that If I ever rebuild the engine don't bore it out at all. Just hone the cylinders and put new rings in it because the thinner cylinder walls will cause it to overheat. Being a young kid I did exactly what he said not to do. I had it bored 30 thousandths and put new pistons in and had the head totally redone. Wouldn't you know it? It constantly overheated. My question is... was that typical for a 1200 engine that's been bored? What about the A14 and A15 engines? Did I totally screw up that engine? I sold it not too long after the engine was rebuilt so I don't know how long it ran.
I was wondering so I thought I'd go to the professionals.
What about it guys?

Thanks

I would think the small radiators on the stock 1200 is more of an issue , living in a similar desert climate I can tell you when ours was a street car it ran really warm over 4000 RPM's , which would be any time you were on the freeway.

Some of the other guys here have actaully bored ther engines and can answer better than I , but after 5 years or so on this forum I've never heard of any issues.

Tom

that sounds like nonsence to me.
why would the thickness of the walls make it overheat more?

I'd say if the engine is old enough to need a bore then you need a new radiator core.

i have an A15 bored slightly and a15's have the thinnest walls, doesn't overheat with a working radiator and fan.

did you ever actually overheat?

Never actually overheated but dang near did all the time. With the cylinder walls being thinner,wouldn't that allow more heat to transfer to the water jackets creating and overheating condition?

The heat has to go somewhere, the engine soaks up heat until something like water ( or oil ) soaks the heat up and radiates the heat away, otherwise the whole thing would get very hot and glow.

you might say a thinner cylinder wall would warm the coolant up slightly faster, but the same amount of heat has to be carried away, and a few thousandths of metal don't take very long for the heat to move through.

a little higher compression and a little harder driving might overheat a car with a radiator not quite up to the task already.

Makes sense. Thanks for the info. I'm going to be putting in AC in my 73 coupe. Would you or anyone else know what type of car I can get a bigger radiator from that would be a descent fit for my 1200?

i think i used an early nissan sentra radiator since it had a bung for an electric fan already and i had several and it was from a 1.6 liter so it's more than big enough. Then had it recored with a higher density core and added an electric fan. Also, sentras had A/C so you could get the whole thing together, with AC you will want an electric fan anyways.

another thing, factory temp gauges have weird scales, the lowest on mark might be 170 and the middle 200 deg and start of red maybe 220 or something. I'd be freaked if my engine got up to 212 ever, the temp will also vary with the ambient temp, so when it starts to get warm out you might get a 10 -15 deg increase in the temp on the road, that could put you right up to the red mark, which isn't really bad if you know what temp it's at.

they dont actually overheat from boring but there is more direct thermal heal transfered from the combustion camber to the coolant and oil gallaries from my understanding... the a12 stock radiator cant cope well with heat, as most aussies know.
As with a14/a15 transplants a radiator swap to a bigger unit usually keeps it all in check.

This has always been my experience

I bored my 1200 block 3mm [0.120"] & drove it for about 100,000 miles, then bored it another .5mm [0.020] & drove it for another 60, or 70,000 miles & never had a problem. I'd say that your brother in law still has plenty to learn about the motor trade.

When an engine is dismantled for reconditioning, the coolant galleries dry out & the crud that has accumulated there over the years shrinks & cracks. If the welch plugs are not removed, & this stuff properly cleaned out, then a great deal of this crud comes loose in the freshly rebuilt engine & starts to circulate. Fortunately the OEM coolant filter quickly traps this foreign material to prevent it from returning to the block. This filter is better known as your radiator.

If the block is properly cleaned, the radiator serviced & cleaned & a cheezecloth [or other] filter is used in the cooling system, you will have no problems at all.

I run a stock 1200 with auto trans & my most recent problem was overcooling, but I have a new radiator core & a regularly serviced filter & I am constantly surprised at just how much rubbish it traps. A new thermostat fixed the problem for me.

Make sure that youre whole cooling system is clean & serviceable, & you too will enjoy trouble free motoring.

intresting,im going to be converting my 120y a12 auto to a a14 manual soon i was going to buy a brand new radiator same as wat i got. as mine is almost stuffed will this be bigger enough??? or will i need bigger??
any ideas anyone..