Radiator question

[Rufas]

I have a 1970 GMC 2500. That my parents purchased new in 1970. Five years ago I went completely throught it. It's not a frame off restoration but close.

The engine is a 300 hp 350 SBC crate engine from GM performance. The engine has a small Weiand 142 supercharger, FiTech EFI, original 4 core radiator (great condition) and 700R trans. It's fully bagged with Ridetech 4 link rear suspension.

The truck runs great, no issues at all. Engine temps runs between 179⁰ and 183⁰ while driving. Because of the supercharger I can't run a fan clutch. Belt system is serpentine with a 19 inch 6 blade fan and factory fan shroud. The only issue is when stopped in traffic I get a slow increase in engine temp. Temp will keep climbing until I start moving, then immediately the temps will decrease.

Before I installed the 6 blade fan and shroud I had duel electric fans with shroud. That did not cool as well as the fan blade and shroud.

I've done research here on aluminum radiators but I wondering if going to an aluminum radiator will really help cooling at idle. I really don't want to spend hundreds of dollars on an aluminum radiator and not fix this cooling issue.

Who makes a good aluminum radiator that not going to break my bank account. What brand, type, rows, fin count per inch etc.

Any info is greatly appreciated.

Last photo is how this truck looked in 1970.

[Steeveedee]

It is more of an air flow issue at idle, since it cools down when you are moving. I guess you could try a fan with more blades or a higher pitch?

[Rufas]

Originally Posted by Steeveedee

It is more of an air flow issue at idle, since it cools down when you are moving. I guess you could try a fan with more blades or a higher pitch?

It's a heavy duty 19 inxh, 6 blade medal non flex fan. Nothing else available. It's also reverse rotation so what choices there are, are very limited. I can go a larger diameter because of the opening of the fan shroud. The fan moves tons of air wirh lots of fan roar.

[72c20customcamper]

What does it creep up to? Does it overheat or just gets to say 210 ? All engines will creep up after running at speed and then stopping and idling . If it gets to hot at idle and cools at speed 40 mph or so it’s an airflow problem not a radiator problem . Location of the fan blade can effect the performance to far in or out of the shroud will greatly effect it . The fan blades should be about half way into the shroud . I would start with making sure the shroud is sealed all around the radiator air like water will follow the path of least resistance

Edit: also the head temp may be getting up there but the actual water temp may be much lower . I’ve seen my gauge go to 215+ in the head but the fans don’t kick in because the water temp hasn’t reach 195 the sensor for my fans are in the radiator next to the inlet hose

[PbFut]

Electric fans put the original electric system into fits unless you up the alternator and rework the battery guage wiring. I put electric fans on my truck but now realize it was not worth the effort. Is it possible the serpantine system you are using is spinning pump and fan too slow? Can you reduce the pulley size on the water pump increasing the pump rotation per engine rpm?

[Rufas]

Originally Posted by 72c20customcamper

What does it creep up to? Does it overheat or just gets to say 210 ? All engines will creep up after running at speed and then stopping and idling . If it gets to hot at idle and cools at speed 40 mph or so it’s an airflow problem not a radiator problem . Location of the fan blade can effect the performance to far in or out of the shroud will greatly effect it . The fan blades should be about half way into the shroud . I would start with making sure the shroud is sealed all around the radiator air like water will follow the path of least resistance

Edit: also the head temp may be getting up there but the actual water temp may be much lower . I’ve seen my gauge go to 215+ in the head but the fans don’t kick in because the water temp hasn’t reach 195 the sensor for my fans are in the radiator next to the inlet hose

The fan shroud is tight fitting around the radiator. The fan is slightly to far into the shroud opening. But because of the supercharger pulley and belt I can't move the fan out any. The fan is less than 1/4 inch from pulley and belt.

You make a good point about sensor location. The high temp I'm worried about is the head temp. So far 215° has been the highest temp, but the outside temp was only 77°. The radiator inlet temp was just under 200°. What concerns me is the summer time temps here typically approach 120°. Most days temp hover around 115°. So I can imagine this condition will get worse.

[Rufas]

Originally Posted by PbFut

Electric fans put the original electric system into fits unless you up the alternator and rework the battery gauge wiring. I put electric fans on my truck but now realize it was not worth the effort. Is it possible the serpentine system you are using is spinning pump and fan too slow? Can you reduce the pulley size on the water pump increasing the pump rotation per engine rpm?

All wiring in this truck has been replaced. I have a PowerMaster 160 amp alternator. The 160 amp alternator without using the the electric fans is now an overkill. Eight gauge wires ran directly from the battery to the electric fans via relays. Alternator output cable is six gauge.

The water pump pulley is the smallest available. Any smaller and the pulley would rub on the water pump housing.

[72c20customcamper]

Originally Posted by Rufas

The fan shroud is tight fitting around the radiator. The fan is slightly to far into the shroud opening. But because of the supercharger pulley and belt I can't move the fan out any. The fan is less than 1/4 inch from pulley and belt.

You make a good point about sensor location. The high temp I'm worried about is the head temp. So far 215° has been the highest temp, but the outside temp was only 77°. The radiator inlet temp was just under 200°. What concerns me is the summer time temps here typically approach 120°. Most days temp hover around 115°. So I can imagine this condition will get worse.

215 in the head is not overheating at idle . The fan being to far in is a problem it will cause the air to swirl and for lack of a better word cavitate in the shroud . My Chevelle will hit 215 -225 in the head before the fans kick in . You said you had electric fans what brand ? I had some Flex-A-Lite fans on it and it was always borderline would take a good while for the temp to go down I replaced them with an aluminum fan shroud and Spal fans the temps will almost instantly drop as soon as they kick in . They use less power and cool 100% better than the Flex fans rated at the same CFM the Flex fans also had an aluminum shroud .

My new truck build I’m putting in a Cold case with dual Spal fans with the aluminum shroud that can with the radiator. The fans that came with the radiator just look cheap in my opinion.

[Rufas]

Originally Posted by 72c20customcamper

215 in the head is not overheating at idle . The fan being to far in is a problem it will cause the air to swirl and for lack of a better word cavitate in the shroud . My Chevelle will hit 215 -225 in the head before the fans kick in . You said you had electric fans what brand ? I had some Flex-A-Lite fans on it and it was always borderline would take a good while for the temp to go down I replaced them with an aluminum fan shroud and Spal fans the temps will almost instantly drop as soon as they kick in . They use less power and cool 100% better than the Flex fans rated at the same CFM the Flex fans also had an aluminum shroud .

My new truck build I’m putting in a Cold case with dual Spal fans with the aluminum shroud that can with the radiator. The fans that came with the radiator just look cheap in my opinion.

The electric fans I replaced were Spal fans with shroud. They would kick in and I still had temp crepe. At freeway speeds the temp still increased when they kicked it. Speeds below 60 mph they worked ok. Those fans seemed to be restrictive above 60 mph.

Now with the 6 blade heavy duty fan (non flex) and no fan clutch I can cruise freeway speeds and climb hills greater than 6% and my temp stay between 179° to 185°.

My radiator is the original Harrison 4 core. It's in great shape but I'm starting to wonder if have it 'rodded' out would help. The problem is finding a radiator shop that can still do that.

[72c20customcamper]

Originally Posted by Rufas

The electric fans I replaced were Spal fans with shroud. They would kick in and I still had temp crepe. At freeway speeds the temp still increased when they kicked it. Speeds below 60 mph they worked ok. Those fans seemed to be restrictive above 60 mph.

Now with the 6 blade heavy duty fan (non flex) and no fan clutch I can cruise freeway speeds and climb hills greater than 6% and my temp stay between 179° to 185°.

My radiator is the original Harrison 4 core. It's in great shape but I'm starting to wonder if have it 'rodded' out would help. The problem is finding a radiator shop that can still do that.

The electric fans shouldn’t be coming on at highway speeds . Mine never do so with this bit more info I would say the radiator needs attention . Your fan right now being it’s not a clutch fan is “on” 100 percent of the time .

Not easy finding a radiator shop these days as with all the competition of aftermarket items and the EPA guidelines most shops closed their doors .

[425HP409]

Originally Posted by Rufas

The fan shroud is tight fitting around the radiator. The fan is slightly to far into the shroud opening. But because of the supercharger pulley and belt I can't move the fan out any. The fan is less than 1/4 inch from pulley and belt.

You make a good point about sensor location. The high temp I'm worried about is the head temp. So far 215° has been the highest temp, but the outside temp was only 77°. The radiator inlet temp was just under 200°. What concerns me is the summer time temps here typically approach 120°. Most days temp hover around 115°. So I can imagine this condition will get worse.

The problem appears from what you have said is that the fan is too far in the shroud. It must be about half in and half out. By being too far into the shroud, at idle the fan will just cavitate air around in the shroud as opposed to pulling it through the radiator and out the back of the shroud. You also mentioned fan roar, this can be caused by the fan being too far into the radiator causing a cavitation. Since you can't move your fan back, a solution would be to trim the shroud.

[72c20customcamper]

Originally Posted by 425HP409

The problem appears from what you have said is that the fan is too far in the shroud. It must be about half in and half out. By being too far into the shroud, at idle the fan will just cavitate air around in the shroud as opposed to pulling it through the radiator and out the back of the shroud. You also mentioned fan roar, this can be caused by the fan being too far into the radiator causing a cavitation. Since you can't move your fan back, a solution would be to trim the shroud.

I think his fan roar is also the fan is direct drive always on . I’m leaning more towards the radiator now that he stated the electric fans would come on at highway speeds . That shouldn’t happen the fans can’t pull as much air as the flow at 60mph . Only time I heard electric fans come on at highway speeds is when I’m towing . Don’t cool it at all since the cfm going through the radiator is higher than the fans capacity .

[68 P.O.S.]

These statements tell me its not the radiator; it is an airflow problem: "Engine temps runs between 179⁰ and 183⁰ while driving" & "The only issue is when stopped in traffic I get a slow increase in engine temp". If the radiator was the problem, the temp would also increase at speed.

Looks like your choices are to either trim the shroud back to expose more of the fan, or reinstall and correctly setup those electric fans. If your e-fans were still running at speed, they weren't setup properly.

[weq92f]

.

Last summer I solved my idle temp creep. In my case it was an airflow problem.

The solution for me was to replace my dual electric fans with spal fans that actually move air. The two 14" fans I had been running were cheap generic 40 dollar fans off eBay that I purchased from Champion radiator with them saying it would cool up to 500 HP or whatever. Those fans were a ripoff.

I had my Copper/Brass 4 core original radiator rodded/repaired and with it all back together with the spal fans and a 190 degree thermostat, all is well in summer idling. At speed the temps hover below the the threshold of fan activation (190). At idle the fans will cycle on/off keeping the temps below 200. I have the system wired to activate one of the dual 14" spals and a pusher fan on my condenser whenever the A/C clutch is engaged. Otherwise, one fan activates at 190 and the second activates at 195.

Before these changes, I had to turn off the A/C at stop lights sometimes to stop the heat creep.


Hth,

-Kevin

[Rufas]

Originally Posted by 72c20customcamper

The electric fans shouldn’t be coming on at highway speeds . Mine never do so with this bit more info I would say the radiator needs attention . Your fan right now being it’s not a clutch fan is “on” 100 percent of the time .

Not easy finding a radiator shop these days as with all the competition of aftermarket items and the EPA guidelines most shops closed their doors .

The reason the fans come on at freeway speeds is I have set the fans 'ON' temp to 190°. So anytime, regardless of speed, when the temp exceeds 190° the fans come on. Even with the fans on the temp would increase.

I don't have any temp creep with the medal fan installed.

[Rufas]

Originally Posted by 425HP409

The problem appears from what you have said is that the fan is too far in the shroud. It must be about half in and half out. By being too far into the shroud, at idle the fan will just cavitate air around in the shroud as opposed to pulling it through the radiator and out the back of the shroud. You also mentioned fan roar, this can be caused by the fan being too far into the radiator causing a cavitation. Since you can't move your fan back, a solution would be to trim the shroud.

The main reason for fan roar is there is not any fan clutch. The fan runs 100% of engine speed all the time.

[weq92f]

Originally Posted by Rufas

The main reason for fan roar is there is not any fan clutch. The fan runs 100% of engine speed all the time.

.

Yep I had straight fan before going to electric. It was loud and I think caused the BBC to drink more fuel.

-klb

[72c20customcamper]

Originally Posted by 68 P.O.S.

These statements tell me its not the radiator; it is an airflow problem: "Engine temps runs between 179⁰ and 183⁰ while driving" & "The only issue is when stopped in traffic I get a slow increase in engine temp". If the radiator was the problem, the temp would also increase at speed.

Looks like your choices are to either trim the shroud back to expose more of the fan, or reinstall and correctly setup those electric fans. If your e-fans were still running at speed, they weren't setup properly.

Yes but his fan is running at full force 100% at highway speed since it’s direct drive .The op also stated that with the electrics they would come in at highway speed .Electric Fans should not come on above 40mph let alone highway speeds unless you are lugging going up hill towing . That indicates a radiator problem, it may be a combo of both .

I can drive all day at 40 and up fans never kick in temp may climb going up hill but never go 190 in the head . The water temp would be 10 degrees lower . I do have a Dewitt’s 2 row with 1.25 “ tubes .

Also the OP stated the temp went to about 215 max at idle which is pretty much normal for any engine . There’s always a rise it head temp after running and coming to a stop