I've been doin' a top overhaul, since the thermostadt went out on our '65 -240cu.in.six cyl. Recently installed a new 350 Holley, ran good for a while, but it overheated, and blued and weakened all the valve springs, so we got exaust leaks. I'd never had weak valve spring syndrome before, in any of my vehicles.
I was replacing everything outside the engine with new stuff and I was surprised to discover a transmission cooler/heater piped (steel tubing and rubber) )into the engine block and returning to the radiator. The hoses and steel going to the transmission were all rotten and leaking. If I'd waited a month or so it would'a ruptured for sure. Anybody know what' s the chance of water leaks inside the automatic transmission with a forty year old cooler???

 

You would get trans fluid in the coolant if there was a leak in the trans cooler system. The tranny fluid is a higher pressure than the cooling systyem, so it forces the trans fluid into the coolant.

 

What happens when the cooling system is at operating temperature or higher and the engine is turned off, causing loss of transmission fluid pressure? Would that not allow the coolant to enter the fluid line? I'm not sure, just wondering.

I don't understand how a failed thermostat caused all that head damage. I always thought aluminum heads were the ones that caused problems after overheating. I sure have overheated my share of engines and never had to fix anything other than what caused the overheating. I wonder if there was some pre-existing condition that was compounded by the high temp.

 

Sounds like your problem could have also been a lean condition, possibly when the carb was changed. Jets too small, vacuum leak, etc. What color are the plugs? Are you pulling the head? If so, check piston condition.

 

I concur with Greg, ATF may intrude into cooling system when the engine is running because of High PSI, true enough. With "Op Temp" shutdown, coolant PSI rises while ATF PSI drops & Coolant will indeed intrude into A/T, wreaking Havoc the next time a start up occurs if/ when it does intrude. 1st it kills the clutches then the seals & O-rings and it makes the ATF as thick as Elmers Glue.

Also Valve springs do wear out & go bad over time. Inline engines tend to suffer from that more, especially in the center cylinders near where the exhaust manifold has the greater bulk & mass. Cleaning springs in carburetor cleaning dip tank stuff kills 'em too.

I'm curious how so much heat was generated to cause valve springs to lose temper, but rest of an engine is unscathed by it. It would seem to me mass of an engine block & cylinder head is more heat sensitive than coiled springs with oil bathing them. If the internal temp got hot enough to ruin the springs, there has to be other damage, or so it would seem to me. I know I'd check that out for sure if it was mine.

I had an experience with asphalt residue/ dust, caused by those grinders used to re- surface asphalt roadways. A 66 E-200 Vans have a low forward belly pan air induction to reach midship position of radiator & engine. Dust lodged in radiator fins & in no miles at all engine heat was off the scale. Engine would not shut down with key turned off. Eventually it did quit, but by then damage was total, complete & fatal.

It took a crate engine to repair, or more corectly it took a replacement engine and I opted for a crate engine to repair it. I ran that Van for several more years, until the salt from an ex riding on the beach [against my wishes & without my knowledge] took its' toll on the unit body (frameless) construction. A tough loss that Ol' Van, don't miss that "Ex" tho'. Heh heh heh heh. . . .


FBp

 

I just went through this with my 66 2wd, the cooler is mounted on the trans with water going from the bottom radiator hose and the block to the cooler. On mine the cooler was plugged and the line were rotten and leaking. dI put in a radiator for a 78 F-100 with a cooler inn it and removed all of the old system, plugged the holes in the block and put in new bottom radiator hose. Ran new lines, using 4' off premade 5/16" brake line.

 

If you had tranny fluid in the water system it would look just like pepto. And it is no fun to clean out of the water system.