i have a 1978 chevy k-20 with a 454 big block and i can't seen to keep it cool. it has a heavy duty 4 core radiator, no thermostat, and dual electric fans. this is a mud truck not a street truck so i am not moving very fast. the truck get ran very hard when i get it out. it stays cool for about 15 min. when it warms up it wants to run between 190 degrees and 200 degrees. after that it jumps to about 220 and i usually shut it off at 230. any ideas would be helpful.  

This is easy to fix. You have done two big things wrong here. First no Tstat, you always run one as many engine run hotter without one. Try a 180. Next scrap the electric fans. I do not understand why so many think that they are the in thing to have in a off road vehicle that is going slow and working hard. You need a good engine driven one with a cowl/shroud around it. You can either use a properly calibrated HD clutch fan or a flex fan (I would go with flex fan if you play hard in heat, sure you will hear it but it is good because it is keeping engine cool and under hood temps cool too.) but SCRAP THE ELECTRICS. The reason for this is that a engine driven fan can easily move 30 to 40 thousand CFM when needed even with the pressure drop for restrict of core. To do this it takes HP 7 to 10 HP and more and you cannot do that easily with a electric fan. To do so would take 300 to 400 amps at 12 volts minimum (are about as much as your starter) BB's make a lot of heat and it takes a lot of air to move it out of radiator effectively. (the hotter it is out the more air you have to move) Your aftermarket fans cannot begin to deal with this. They advertise high CFM flow but it pales to your real needs here and that rating is not with a core stack nor does it factor in how as air heated up and expands going through core this adds to back pressure and between core and expanding air you are likely not even getting 1/2 of its CFM rating.(if even that) Do what I say and your cooling problems will be history.  

i will try the t-stat but there is no room between the radiator and water pump for an engine driven fan.  

You are not going to fix this with electric fans and a BB and off road operation. You need to move a lot of air at low speeds. Relocate radiator a bit or use a thinner one if need be but get a engine driven fan in there. It is strange that you have no room because there should be a lot of room if engine and radiator is in correct place in that body style.  

i thought about moving the radiator to the bed but i don't want to loose my entire bed. i already have a large fuel cell in the bed. the electric fans pull twice as much air as my previous mechanical fan. i think a different radiator and water pump are in order. i have been looking at aluminum radiators and higher flowing water pumps  

1978k-20:
i thought about moving the radiator to the bed but i don't want to loose my entire bed. i already have a large fuel cell in the bed. the electric fans pull twice as much air as my previous mechanical fan. i think a different radiator and water pump are in order. i have been looking at aluminum radiators and higher flowing water pumps

You are mistaken on the real world capacity of aftermarket electric fans. It takes HP to move serious air and that takes engine power or a LOT of electrical power. It takes about 80 amps to generate one HP with 12V electric which means you would need to overload electric system to get the needed HP for a serious fan in there. If mechanical fan was not cutting it it was because you had wrong one as a proper one can move air that electrics can only dream about. Electrics can work on small cars with small heat loads and that relies on ram air for most cooling. My 2000 K3500 never thinks about overheating even with A/C on and towing a very heavy trailer even in traffic. Hottest it has ever been was near 210 and that was briefly on only a few times and it is usually around 190 or so. It had a 10 bladed HD clutch fan and it moves serious air when needed and I have even heard it come in a speed on grade with a heavy trailer when it is hot and temp gauge stays stable. Even my old 89 4x4 burb has never overheated or close to it since I bought it new and it has seen temps of over 105 in travels and I always use A/C and never run with windows down. A few years ago I was driving thru Mesa Verdi in southern CO when it was in high 90's in thin air and it is slow going with steep grades and windy roads and it stayed cool and we did too with A/C while the HD clutch fan on it clawed in the air needed to do the job. (it was really "talking" at times too) Another summer I started up the BearTooth Pass climb from MT with a GVW of around 7500 lbs (we were really loaded down) and  when it was 100 out and we climbed long and hard and did not get below 90's until we had climbed close to 4000 feet and it never lost its cool or though about it. If it had been electric only, it would have puked out very early in the climb.  

you are doing some thing totally different with your truck than what i am doing. your truck is moving down the road at high way speeds. i am not and my engine speed is a lot higher also. i appreciate the advice but the electric fans are going no where. no room for a mechanical fan. i think i might have an air pocket stuck some where in the cooling system that can't get out.  

Hey Sno

Gotta love those that come on and ask for help but dont want to listen to any advice. They think they know what the problem is and that your solution is wrong. Well if they know what the problem is why did they ask the question in the 1st place?? You say your engine is running a lot harder than his. So is your electric fan running faster to compensate for this? You may not be getting the 60-70mph wind through the grill that he was but if you had a mechanical fan it would also be pulling in 2 times more air due to running such higher rpms. Im gonna have to agree with Sno. It sounds like you either need to totally revamp what your setup or get use to taking breaks every 30 minutes.  

never said my engine is working harder. my point is that his truck is going down the high way mine is not. this is not the first time i have had a problem keeping this truck cool. i could not keep the small block cool with a mechanical fan and it had a shroud on it.  

Riddle me this, what electric fans are you using and do they have a shroud?  

they are off a 98 olds aurora. thay have the factory shrouds/mounting brakets thay come on them  

not sure on the exact diameter. they move a lot of air.  

fedspunisher:
Hey Sno

Gotta love those that come on and ask for help but dont want to listen to any advice. They think they know what the problem is and that your solution is wrong. Well if they know what the problem is why did they ask the question in the 1st place?? You say your engine is running a lot harder than his. So is your electric fan running faster to compensate for this? You may not be getting the 60-70mph wind through the grill that he was but if you had a mechanical fan it would also be pulling in 2 times more air due to running such higher rpms. Im gonna have to agree with Sno. It sounds like you either need to totally revamp what your setup or get use to taking breaks every 30 minutes.

You guys do not get it, it takes HP to move a lot of air effectively and unless your electrics are using a couple hundred amps for starters, they do not have the HP to do it. You take a engine driven fan that can use 10 HP and more moving air at time and replace it with maybe 1/4 HP of electrics.

Lets do some math here. It takes .24 BTU to heat one pound of air 1 degree F and there is  approx 387 Cubic feet in one pound of air at standard temp and pressure. So if you want to dissipate say 400,000 BTU you need to move 400,000 /.24 = about 2,100,000 cubic feet of heat heated one degree or about 42,000 CFM for a 50 degree air rise or 21,000 CFM with 100 degree rise. To make say 250 HP with a gas motor you need to burn fuel at a rate of about 16 to 20 gallons a hour or about 2 to 2.5 million BTU's of heat release in fuel. About 25% is converted to work, about 50% goes down tail pipe and around 25% around cooling. (some time least thru pipe and more through cooling) Assuming this that means 500,000 BTU needs to be "lost" through radiator.  Real world you are not going to see 100 degree rise and more like 50 give or take and as air is warmed and closer to core temp, less heat is removed from it. This is why you need a serious engine driven fan. BTW, approx 4 square feet of radiator area will see about 20,000 CFM at 60 MPH with no fan. Also lower temp Tstat's REDUCE radiator efficiency because there is less temp differential between core and air passing thru it.

There is a lot more to proper cooling than meets the eye here.  

Lets muddy the water a little bit more here. At lower RPM's a greater percentage of the heat of the "burn" is transferred to block/cooling system because it is in cylinder longer per expansion cycle and during this time some more of the heat is transfer to it. Example, at 2000 RPM if you consider a 120 degree power expansion stoke that means burning mixture is in cylinder for 10 ms. As mixture expands it cools too but is is still confined longer than at say 4000 RPM when power stroke lasts 5 ms. Granted more combustion is taking place in block as far as fuel consumed but the total time of power stroke is the same (ie you get two 5 ms strokes at 4000 RPM in same time frame as you get one at 2000 RPM). Since hot gas spends less time in cylinder during burn cycle at higher RPM's (it is expanded and dumped quicker) less heat is transferred to cylinder as a percentage of total power/heat consumed. It is also dumped quicker and EGT rises as higher average percentage of heat is dumped through exhaust. This is why it can be harder to cool a engine at 2000 RPM making over 100 HP than same engine making same HP at 4000 RPM. When they design a cooling system they take a "guess" at the average heat load (average HP and RPM) that has to be dumped and cool accordingly. Big blocks can be tuff to cool because they have more power but more surface area to the grab/take heat for expanding gasses. All of this can be overcome with proper positive airflow with proper engine driven fan though.  

I was agreeing with you sno.