Another Overheating Question.....A long Post

[drag-200stang]

mraley,

Nice car!!! I ran .060 over on a YF tri-power, over 11:1 compression (this is when you could get good gas), headers, 266 duration solid lifter cam, with a 4-speed top loader. This was a daily driver. Stock cooling system except for after market fan with no overheating issues. Your automatic probably puts more heat into the cooling system. I agree with others on less overbore is best.

 

[MustangSix]

I think sixpacker hit it in his post. An overbored engine produces more heat. It's the additional heat, not the thinner wall, that causes a problem.

I'll hazzard one more observation as well. Usually when an engine is ready for an overbore, it's probably got a lot of miles. The rest of the cooling system has seen better days. There's years of accumulated rust and debris in the block. When the engine is reassembled, the cooling system is now probably marginal for the increased power and displacement, so you get an overheat. Blame the overbore.

Speaking of rebuilds, I helped a guy with a 289 cure a serious overheat problem. Seems he put the left head gasket on backwards. The engine sealed, but the coolant bypassed the block and head. Of course, he blamed it on the machinist and the overbore until I showed him where the gasket was marked "front".

 

[Anonymous]

Bad news. I added the world's largest fan shroud (3.5" from NPD). It's running hotter now if anything. It felt well below 90F on my way home today, and even at speed the engine was up nearly to 3/4 on the temp gauge. I would guess that shroud is so thick that it's too close to the motor and is actually restricting the air flow. Too bad, I paid 80 bucks for it. Maybe I'll try to return it.

Anyone know who makes an aluminum radiator for a 200?

BTW, the old 60-over 289 block had been recently rebuilt by the previous owner. I imagine they hot tanked it before they bored it out, but I don't know if I could tell the difference. Rust was coming out and clogged my radiator twice. I added one of those Gano coolant filters which worked really well.

The new block is brand new standard bore. I went with a 302 crank, so the displacement is very close to a 60-over 289 (298ci).

What really convinces me about 60-over not being a good idea is that my 200 is running hotter now, especially around town. Of course I also changed to a 250 head and a hotter cam, 2-barrel carb, headers... I still don't see why that would produce more heat if I'm just loafing around with it.

It used to have a 195 deg thermostat, now it's 180. Maybe a little extra backpressure in the block was helping the cooling?