Time for a Radiator Upgrade...?

[Bextreme04]

.60 over 350. running this combo for 21/2 years now. I didn't put the 160 in for the trans specifically. one of the best running small blocks i've ever had. Tell me why you think this is too cold even though i have no intention of changing it.

As with most things, engine operating temp is a compromise and running hotter or colder is really dependent on what you are doing with it. Colder is better if you are running WOT a lot and you want every little bit of extra top-end horsepower you could possibly get. It has been shown on a dyno that colder coolant temp will almost always translate to a few extra horsepower on the top end.

The warmer temp(210 operating temp on a 195 thermostat) is what OEM's usually spec for their engines. There are a few reasons why this is the standard and the big one relates to how close that temp is to the boiling point of water. By running the engine a few degrees over the boiling point of water it ensures that any moisture contamination in the oil is burned off to help with longevity and cleanliness of the engine internals and oil. It also aids in fuel mixture in the intake and combustion efficiency while also letting the oil run a little thinner to lower rotating losses.

In other words, cold is better for drag racing and hot is better for driving efficiency and longevity. YMMV

You wont start getting into danger areas for the engine until the 240-250 degree temp range and 50-50 coolant doesn't boil until 260+ in most cases with a functional pressurized system.

 

[AuroraGirl]

Looking at your pictures, the radiator is obviously plugged. By the time a radiator is that old, it's corroded junk. Just put a new one in and be done. If you waste your money trying to clean it, it will probably leak.

The radiator in my '73 was plugged and leaking. I put a new 4 core in it. No use messing around trying to fix junk.

a professional shop can clean them and also fix leaks and pressure test, usuallyy. but the cost does run about a new aluminum rad, too. so thats something to consider.

also not using tap water goes a long way for cooling system maintenance. basically if it doesnt have minerals and is just the coolant and pure water, the scaling is minimal because there isnt any contamination added and the galvanic and rust corrosion is down because there isnt an electroylte for corrosion to occur. THe minerals in water make it conductive, if its got no minerals its a lot harder for the process to happen that is what attacks that solder joints and leaves scale on the whole system.

 

[AuroraGirl]

@7900_Blazer

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This is just a randomn example I found, but when I mentioned your fan sits far into your shroud, it should barely protrude out the back but not sit inside it. if you drop the spacer, get a new fan, and install a fan clutch, I have a feeling you would probably be right where you need to be. Im not sure who made your truck have a direct drive fan, but im guessing that is not a good combo for a flex fan. constantly stressed id think. The position on the shroud encourages proper airflow too
my bad, I just looked up, apparently a flex fan doesnt use a cluthc. I would recommend a solid fan and clutch tho, personally. but its by design but i think its still sitting too far, maybe.

If you decide to keep the fan you have, if you want a different spacer I have a **** load I could prob find you one a different length if it was ever needed

 

[Bextreme04]

I'm still pretty sure the flex fan was put on there to try and overcome the lack of cooling at idle. I saw an enginemasters episode where they were looking at power loss from fans and the flex fan lost as much power as a solid fan with no clutch, to the tune of something like 30hp at higher RPM. It doesn't really cool any better either. I would fix the rest of the cooling issues(radiator and add the overflow back on) then replace the fan and spacer with the correct fan and clutch. Make sure you have a good quality new cap on there too. You should have coolant all the way up to the very top of the radiator when you open the cap, you should never see air in the radiator when you open the cap cold.

All of this will help your cooling, but will still not fix the underlying issue that the stock non-return line fuel system easily gets into vapor lock, and you should add the return line to get rid of your drivability and reliability issues. Even with a perfectly operating cooling system you can get vapor lock on the non-return line system, but it will usually show up as the temperatures shoot up on engine shut-off

 

[peats]

well unless you have a high compression ratio esp compared to stock for the year, the engines are lower compression in general and they run cooler to begin with. if its not smogged, if it has headers, etc, it wont be holding a lot of heat in the engine. and at 160 you are slightly below the optimium temperature for combustion chamber, potentially, and that is more dependent on your heat range of plug and if you hae forced induction often times, and of course, timing over all. i dont know your setup obviously, but if its, for example, a bored over 350 with no smog components and maybe just external HP gains maybe getting it near 300, maybe sub, with the factory heat range plug and stock timing spec, maybe you run manifolds or maybe not, you could be below optimum temp. Power isnt gonna be like suffered suffered, but unless you drive rather exclusively a good 30+ min a day, you may be keeping the crank case cool enough and not dried out. when cool they condense moisture and then you get creamy oil. Hotter temps, closer to the boil point, dont need as long to evaporate the water in the oil. but short trips will negate that idea almost no matter what


but, say, you are pushing some ponies and maybe have some high compression heads or you run 91 etc because it would ping otherwise, or maybe you have a turbo etc etc, you very well may need that 160 t stat to keep your combustion chamber the right temp. i dont know your truck tho

basically its not like your killing anything, but if you were a stock situation you could potentially make more efficient cleanliness of your crankcase and also with the right plugs keep them from fouling. I forgot to mention that, having the wrong heat range or significantly lower temps around in there could make your plugs foul more.


should have saw how milkshake I got my park avenues crank case when I ran without a t stat for a couple days and it was a cool, foggy evening and it was hot the time I parked. Took a while to get it not milkshake, but it was a no-stat scenario vs a lower. If i use a 180(lower my car calls for) in winter and dont block the radiatiro, the car struggles to break 150, 160 in driving scenarios. In city it will eventually get 180 but that temp stuff is significant to the PCM for torque converter lockup, but thats a electronioc controlled transaxle, i doubt you have that worry in your truck

 

[peats]

well unless you have a high compression ratio esp compared to stock for the year, the engines are lower compression in general and they run cooler to begin with. if its not smogged, if it has headers, etc, it wont be holding a lot of heat in the engine. and at 160 you are slightly below the optimium temperature for combustion chamber, potentially, and that is more dependent on your heat range of plug and if you hae forced induction often times, and of course, timing over all. i dont know your setup obviously, but if its, for example, a bored over 350 with no smog components and maybe just external HP gains maybe getting it near 300, maybe sub, with the factory heat range plug and stock timing spec, maybe you run manifolds or maybe not, you could be below optimum temp. Power isnt gonna be like suffered suffered, but unless you drive rather exclusively a good 30+ min a day, you may be keeping the crank case cool enough and not dried out. when cool they condense moisture and then you get creamy oil. Hotter temps, closer to the boil point, dont need as long to evaporate the water in the oil. but short trips will negate that idea almost no matter what


but, say, you are pushing some ponies and maybe have some high compression heads or you run 91 etc because it would ping otherwise, or maybe you have a turbo etc etc, you very well may need that 160 t stat to keep your combustion chamber the right temp. i dont know your truck tho

basically its not like your killing anything, but if you were a stock situation you could potentially make more efficient cleanliness of your crankcase and also with the right plugs keep them from fouling. I forgot to mention that, having the wrong heat range or significantly lower temps around in there could make your plugs foul more.


should have saw how milkshake I got my park avenues crank case when I ran without a t stat for a couple days and it was a cool, foggy evening and it was hot the time I parked. Took a while to get it not milkshake, but it was a no-stat scenario vs a lower. If i use a 180(lower my car calls for) in winter and dont block the radiatiro, the car struggles to break 150, 160 in driving scenarios. In city it will eventually get 180 but that temp stuff is significant to the PCM for torque converter lockup, but thats a electronioc controlled transaxle, i doubt you have that worry in your truck

well unless you have a high compression ratio esp compared to stock for the year, the engines are lower compression in general and they run cooler to begin with. if its not smogged, if it has headers, etc, it wont be holding a lot of heat in the engine. and at 160 you are slightly below the optimium temperature for combustion chamber, potentially, and that is more dependent on your heat range of plug and if you hae forced induction often times, and of course, timing over all. i dont know your setup obviously, but if its, for example, a bored over 350 with no smog components and maybe just external HP gains maybe getting it near 300, maybe sub, with the factory heat range plug and stock timing spec, maybe you run manifolds or maybe not, you could be below optimum temp. Power isnt gonna be like suffered suffered, but unless you drive rather exclusively a good 30+ min a day, you may be keeping the crank case cool enough and not dried out. when cool they condense moisture and then you get creamy oil. Hotter temps, closer to the boil point, dont need as long to evaporate the water in the oil. but short trips will negate that idea almost no matter what


but, say, you are pushing some ponies and maybe have some high compression heads or you run 91 etc because it would ping otherwise, or maybe you have a turbo etc etc, you very well may need that 160 t stat to keep your combustion chamber the right temp. i dont know your truck tho

basically its not like your killing anything, but if you were a stock situation you could potentially make more efficient cleanliness of your crankcase and also with the right plugs keep them from fouling. I forgot to mention that, having the wrong heat range or significantly lower temps around in there could make your plugs foul more.


should have saw how milkshake I got my park avenues crank case when I ran without a t stat for a couple days and it was a cool, foggy evening and it was hot the time I parked. Took a while to get it not milkshake, but it was a no-stat scenario vs a lower. If i use a 180(lower my car calls for) in winter and dont block the radiatiro, the car struggles to break 150, 160 in driving scenarios. In city it will eventually get 180 but that temp stuff is significant to the PCM for torque converter lockup, but thats a electronioc controlled transaxle, i doubt you have that worry in your truck

 

[AuroraGirl]

I'm still pretty sure the flex fan was put on there to try and overcome the lack of cooling at idle. I saw an enginemasters episode where they were looking at power loss from fans and the flex fan lost as much power as a solid fan with no clutch, to the tune of something like 30hp at higher RPM. It doesn't really cool any better either. I would fix the rest of the cooling issues(radiator and add the overflow back on) then replace the fan and spacer with the correct fan and clutch. Make sure you have a good quality new cap on there too. You should have coolant all the way up to the very top of the radiator when you open the cap, you should never see air in the radiator when you open the cap cold.

All of this will help your cooling, but will still not fix the underlying issue that the stock non-return line fuel system easily gets into vapor lock, and you should add the return line to get rid of your drivability and reliability issues. Even with a perfectly operating cooling system you can get vapor lock on the non-return line system, but it will usually show up as the temperatures shoot up on engine shut-off

would a 75 have a vapor line returning to the tank? if he doesnt have a charcoal system working, could he get a 3 port filter and just plumb into the vapor line?

trying to think of a way to allow him to test the theory while also not making it a lot of work, basically if it can be easy and then he sees what we mean, that is good for everyone

but i agree. ALl very good ideas, thanks for the bit about the flex fan. never liked them. I just assume have a clutch and solid fan. it just works

 

[AuroraGirl]

As with most things, engine operating temp is a compromise and running hotter or colder is really dependent on what you are doing with it. Colder is better if you are running WOT a lot and you want every little bit of extra top-end horsepower you could possibly get. It has been shown on a dyno that colder coolant temp will almost always translate to a few extra horsepower on the top end.

The warmer temp(210 operating temp on a 195 thermostat) is what OEM's usually spec for their engines. There are a few reasons why this is the standard and the big one relates to how close that temp is to the boiling point of water. By running the engine a few degrees over the boiling point of water it ensures that any moisture contamination in the oil is burned off to help with longevity and cleanliness of the engine internals and oil. It also aids in fuel mixture in the intake and combustion efficiency while also letting the oil run a little thinner to lower rotating losses.

In other words, cold is better for drag racing and hot is better for driving efficiency and longevity. YMMV

You wont start getting into danger areas for the engine until the 240-250 degree temp range and 50-50 coolant doesn't boil until 260+ in most cases with a functional pressurized system.

how much psi is a square usually running? i know my car runs 16 psi on the OE cap, but my ford is 13 PSI and if you dont bleed the system that 13 psi really shows its face when you have air pockets lol.
My old aurora was 18 psi. BUt i assume a square is 15, 16?

 

[peats]

sorry for the technical snafoo, i'm not computer savvy. flat top pistons, RV style cam, aluminum intake, quadrajet,hedders, 2 1/2 " exhaust. running 170 deg. oil is clean at 3,000 mi. and have'nt even looked at the plugs since install (25k). no emissions. essentially no issues with running at 170. we can all have our opinions, that's what this forum is about. i have run my 406 sb k5 with the exact same setup for 12 years now again with zero issues. just saying.

 

[AuroraGirl]

sorry for the technical snafoo, i'm not computer savvy. flat top pistons, RV style cam, aluminum intake, quadrajet,hedders, 2 1/2 " exhaust. running 170 deg. oil is clean at 3,000 mi. and have'nt even looked at the plugs since install (25k). no emissions. essentially no issues with running at 170. we can all have our opinions, that's what this forum is about. i have run my 406 sb k5 with the exact same setup for 12 years now again with zero issues. just saying.

im not saying it would cause issues tho,im saying there is potentially a better temp but the reasons for it arent like world changing. Infact, if you are someone who keeps up the oil religious and you dont just drive from store to store like grandpa who only takes left turns, you probably are fine. bex outlined the good reasons i missed, which he also explained some benefits to the lower temp too.

do you live in a cold climate by chance?

in cold weather you would be surprised at how much different 20 degrees can make the comfort feel, although, a single cab truck like most squares would not have the same space to heat as a full size luxury car, so the heating point may only apply to my car then lol but

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if i dont put a 180(cold t stat) in this beast in the summer monthsm it gets hot. I mean HOT. 215 if the wind isnt blowing at your car hot. 220 in traffic. The humidity and old radiator i think contribute there. BUt if I get into boost, those temps go up fastttt. And I will experience a lot of knock retard which is the computer pulling timing to prevent knock, but it will do it much more proactively than actual knock occurs, which is great to not chip a a piston, but basically, I benefit from the cooler temps in that the computer wont pre-emptively pull timing when you want the boost boost vroom vroom.
in winter time, 180 makes the car run really cold, and even with a 195 you have to block your radiator or give warm up extra time if you want to lock your torque converter and have full heat and proper operating temps. IT wont ever get there if you take off and its cold. Because the low comprression(because boost) the engine just doesnt make a lot of heat when not in boost, and -30 is no joke to warm up on cars here lol

 

[AuroraGirl]

sorry for the technical snafoo, i'm not computer savvy. flat top pistons, RV style cam, aluminum intake, quadrajet,hedders, 2 1/2 " exhaust. running 170 deg. oil is clean at 3,000 mi. and have'nt even looked at the plugs since install (25k). no emissions. essentially no issues with running at 170. we can all have our opinions, that's what this forum is about. i have run my 406 sb k5 with the exact same setup for 12 years now again with zero issues. just saying.

and what kind of plugs you run? My car has ac delco 41-101 which is an NGK iridium, and that handles heat better than platinum, and copper does the best but my waste-spark ignition would eat whatever plugs are connected to the primary tower on the coil if you use them, so you need to replace more often. If I were to use copper i would just put new ones in back, run the wires to the front ones that will waste spark more often, and then replace the easily accessible front ones more often. If I had to kinda thing.

 

[peats]

sounds like your engine is very sensitive to temp. i was mostly trying to help the original post because i have a similar setup that work for me. i would start with a new rad and the stat of his choice and i think he will be fine.

 

[Bextreme04]

would a 75 have a vapor line returning to the tank? if he doesnt have a charcoal system working, could he get a 3 port filter and just plumb into the vapor line?

trying to think of a way to allow him to test the theory while also not making it a lot of work, basically if it can be easy and then he sees what we mean, that is good for everyone

but i agree. ALl very good ideas, thanks for the bit about the flex fan. never liked them. I just assume have a clutch and solid fan. it just works

The problem is that you wouldn't want to replace a vapor line with a return line because the vapor line is replacing the tank vent in applications that have it. The heavy duty trucks(like mine) don't have a vapor return and instead run a hose and wobble check valve on that line to prevent the tank from pressurizing or developing a vaccum. I think that might be the difference in available caps that get people all messed up too. If you have the vapor line running to a canister, you need a vented cap to allow the system to function properly and for vapor to get recovered through the system. HD trucks with a check valve on the vent get the non-vented caps because all of the venting happens through the sending unit vent port. He needs a 4 port sending unit that has filler vent, feed, return, and tank vent on it. He either runs the vent to a check valve and runs a non-vented cap, or he runs the vent to a vapor canister and runs a vented cap.

There really isn't any theory to test on this. The non-return line system is KNOWN to cause vapor lock. The engine cooling system on his truck is KNOWN to be totally f#&$ed up and needs service. If he fixes both of those problems he should never have another problem like this again no matter how hot it gets outside or what he is doing to the truck.

 

[Bextreme04]

sorry for the technical snafoo, i'm not computer savvy. flat top pistons, RV style cam, aluminum intake, quadrajet,hedders, 2 1/2 " exhaust. running 170 deg. oil is clean at 3,000 mi. and have'nt even looked at the plugs since install (25k). no emissions. essentially no issues with running at 170. we can all have our opinions, that's what this forum is about. i have run my 406 sb k5 with the exact same setup for 12 years now again with zero issues. just saying.

Its not really the kind of thing you would notice until you tear the motor apart and look at what may or may not be built up inside of there. I'm sure either way is fine and you might only notice the difference at the gas pump or with a specific side-by-side test. I'm sure the difference in mileage could be easily lost in the mix and variability in carb adjustment, intake differences, etc.. anyways. I'm also sure that the differences are more or less pronounced depending on where/how it is used and the environment you live in like @AuroraGirl stated. A colder thermostat or a high flow race one might make your heater not work as well as it could or cause the engine to not even be able to warm up at all in very cold climates. You might also NEED to run a colder thermostat in VERY hot climates or in vehicles that do heavy mountain towing regularly just to keep it operating in an acceptable temp range.

I'd be interested to see if your engine(or other guys engines) that are running the cold T-stats because they saw racecar guys doing it find that they have extra buildup of corrosion inside the engine or show signs of the milky oil/water sludge gunk in the upper engine area. I've seen that on a few racing engines that do a lot of hot/cold cycling and never really get up to hot conditions. Most tracks require you to not run anti-freeze anyways and you have to have something like distilled water and water wetter in there, which has a lower boiling point.

 

[AuroraGirl]

The problem is that you wouldn't want to replace a vapor line with a return line because the vapor line is replacing the tank vent in applications that have it. The heavy duty trucks(like mine) don't have a vapor return and instead run a hose and wobble check valve on that line to prevent the tank from pressurizing or developing a vaccum. I think that might be the difference in available caps that get people all messed up too. If you have the vapor line running to a canister, you need a vented cap to allow the system to function properly and for vapor to get recovered through the system. HD trucks with a check valve on the vent get the non-vented caps because all of the venting happens through the sending unit vent port. He needs a 4 port sending unit that has filler vent, feed, return, and tank vent on it. He either runs the vent to a check valve and runs a non-vented cap, or he runs the vent to a vapor canister and runs a vented cap.

There really isn't any theory to test on this. The non-return line system is KNOWN to cause vapor lock. The engine cooling system on his truck is KNOWN to be totally f#&$ed up and needs service. If he fixes both of those problems he should never have another problem like this again no matter how hot it gets outside or what he is doing to the truck.

i agree, i was being optimistic because he wasnt really digging the suggestion for return line, was hoping to make it more appealing but you are right, thanks for the insight. my 80 k25(Oh we have the same truck thats cool) was over 8600 gvw or whatever, does that mean I should have had a sealed cap and what all you said? because I most definitely have a differential vent stuck in a short piece of hose on the vent tube and a cap with a vent in it. my grandpa did that. i dotn actually know if i had a canister OE or not, but I imagine yes..? I dont seem to have that bracket on the core support for it, i think. but it could have been removed.

 

[Bextreme04]

i agree, i was being optimistic because he wasnt really digging the suggestion for return line, was hoping to make it more appealing but you are right, thanks for the insight. my 80 k25(Oh we have the same truck thats cool) was over 8600 gvw or whatever, does that mean I should have had a sealed cap and what all you said? because I most definitely have a differential vent stuck in a short piece of hose on the vent tube and a cap with a vent in it. my grandpa did that. i dotn actually know if i had a canister OE or not, but I imagine yes..? I dont seem to have that bracket on the core support for it, i think. but it could have been removed.

Mine is also the 8600GVW and federal emissions. No, canister on mine and I also have the vent tube and cap similar to the differential caps. In our situation it doesn't really hurt anything to have the vented cap. It's just extra venting. The problem comes when you run a non-vented cap on a canister system. Then you end up with a vacuum in the tank and fuel starvation when the pump can't overcome it.