454 radiator

[THE "10" SILVERADO]

Alright, went for a freeway cruise and overheated after 20 miles. I've got a plastic/aluminum radiator in my 77 350 and I'm not getting enough cooling. What is required to switch to a 4 core 454 radiator? Thought I didn't need one and found out I was wrong. I think I'll need the upper bracket as the 4 cores are taller. Anything else?

Thanks,
Michael
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[mrolds88]

Michael, is it a new radiator? What was the original application? Is the thermostat opening all the way? I would double check the thermostat first. I usually take a gutted 180* t stat housing and make a run wih it. See what temps are running then. As far as swapping a 454 radiator, I believe a new set of lower mounts and an upper bracket will do.

[THE "10" SILVERADO]

Originally Posted by mrolds88

Michael, is it a new radiator? What was the original application? Is the thermostat opening all the way? I would double check the thermostat first. I usually take a gutted 180* t stat housing and make a run wih it. See what temps are running then. As far as swapping a 454 radiator, I believe a new set of lower mounts and an upper bracket will do.

New radiator. Swapped old 350 for new so same application. Also my thermostat isnt really working so I'm not exactly sure how hot I am running. Never had a problem till now
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[INSIDIOUS '86]

Well we can tell its not getting enough cooling. If the temp creeps up like that after 20miles on the highway then A: it's not cooling sufficiently B: it's not flowing enough or is flowing to much.

You can try a high flow thermostat and shut off flow to your heater core.

I a big block has a lot of water in it and the radiator that small can only cool a small percentage of that which is why the temp creeps up till it overheats.

I know the big block core supports have nutsert a up top to mount the rad support. So you may need some nutserts as well and the hose size may may be different on the bbc rad but I'm not sure of that
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[donut]

Overheated as what? Puking water or just warmer than you like? What's your fan configuration? Thermostat not working, or just the gauge? Any bubbles in the rad? Cross contamination between engine and coolant? ie oil where it shouldn't be or water in the crankcase?

How's the cooling at idle?
Yes lots of questions, but many overheating threads the OP is actually running where it should be. (OMG, I'm overheating, I've spent hundreds and still creeping up to 200*)

[THE "10" SILVERADO]

Originally Posted by donut

Overheated as what? Puking water or just warmer than you like? What's your fan configuration? Thermostat not working, or just the gauge? Any bubbles in the rad? Cross contamination between engine and coolant? ie oil where it shouldn't be or water in the crankcase?

How's the cooling at idle?
Yes lots of questions, but many overheating threads the OP is actually running where it should be. (OMG, I'm overheating, I've spent hundreds and still creeping up to 200*)

Well my gauge doesn't work at all. I've been trying to troubleshoot since it's stuck on cold all the time but I've been out of town for three weeks and haven't had time.

I've driven around town alot and never had a problem, but I was crusing at 2800rpms and it just got to hot. Pulled over for gas and it was puking water through the cap and shooting steam. Luckily I needed gas when I did.

EDIT: As for fan I have the stock 7 blade fan with a HD fan clutch. Clutch is new and working fine (I believe).

Water seemed clean, didn't see any bubbles or brown coolant (so I don't think any oil contamination).

Put a new thermostat in a couple of months ago when I finished the engine (so far only 2k miles on engine) so I think it should be working fine.

[superwade57]

Originally Posted by INSIDIOUS '86

Well we can tell its not getting enough cooling. If the temp creeps up like that after 20miles on the highway then A: it's not cooling sufficiently B: it's not flowing enough or is flowing to much.

You can try a high flow thermostat and shut off flow to your heater core.

I a big block has a lot of water in it and the radiator that small can only cool a small percentage of that which is why the temp creeps up till it overheats.

I know the big block core supports have nutsert a up top to mount the rad support. So you may need some nutserts as well and the hose size may may be different on the bbc rad but I'm not sure of that
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Upper hose is larger into rad. Its the same as thermostat neck.

What about an elec fan from a 2000-2002 jeep grand cherokee. Theres threads on it here...fits perfect into sbc shroud with very little mods. Add a relay and a thermo switch flows like 4000 cfm and will cost you under 2 bills to do.
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[donut]

You shouldn't need to go to a 454 rad. In my mind, something changed. Unless you were having cooling issues before and that's why the new radiator.
INSIDIOUS '86, made some good points that should be addressed. It cools around town but not on the highway, that kinda points to flow. Either lack of air, or to much water/not enough water.
I'm assuming the rad cap was changed with the new rad? If the cap won't hold pressure, then the coolant will boil at a lower temp. (same with little weepers on hose connections. If they won't hold pressure...) I'm also assuming new hoses, so a collapsed hose could "not" be the culprit.
How about the water pump? I have seen some with the impellers half rotted off. Also had one the impeller broke. It would spin fine at lower rpm, but the crack would allow it to freewheel at higher rpm.

Quick thought, are you sure the new rad is the correct one? No point in a ton of troubleshooting if the rad is wrong from the get go.

[THE "10" SILVERADO]

Originally Posted by donut

You shouldn't need to go to a 454 rad. In my mind, something changed. Unless you were having cooling issues before and that's why the new radiator.
INSIDIOUS '86, made some good points that should be addressed. It cools around town but not on the highway, that kinda points to flow. Either lack of air, or to much water/not enough water.
I'm assuming the rad cap was changed with the new rad? If the cap won't hold pressure, then the coolant will boil at a lower temp. (same with little weepers on hose connections. If they won't hold pressure...) I'm also assuming new hoses, so a collapsed hose could "not" be the culprit.
How about the water pump? I have seen some with the impellers half rotted off. Also had one the impeller broke. It would spin fine at lower rpm, but the crack would allow it to freewheel at higher rpm.

Quick thought, are you sure the new rad is the correct one? No point in a ton of troubleshooting if the rad is wrong from the get go.

First off thanks for helping troubleshoot with me, I'll try to answer everything.

I was going to have the old radiator flushed/cleaned for new engine. Local radiator shop said it had already been worked on previously and that I shouldn't throw money into it. Took it to O'Rielly's and bought a plastic/aluminum radiator the same size (it was a bit thinner than the previous copper core one though but I figured modern tech allowed it to be thinner?).

Water pump is also new. I didn't reuse anything on the new motor except the starter which was fresh already.

UPDATE: I ended up leaving the truck at a gas station because I was busy yesterday. I went ahead and bought a new radiator cap (even though the other was new as well) and drove home. Instead of doing 75 at 3.1k rmps I stayed around 65 at 2.5k rpms. Got home and popped hood and nothing seemed out of the ordinary.

Thinking that possibly the cap just failed and allowed the coolant to boil over even though it wasn't too hot? Not sure. Set aside tomorrow just to fix temp gauge for peace of mind. Still wondering if maybe I should upgrade to a bigger radiator if one of my friends has one laying around which is quite possible.

[INSIDIOUS '86]

When you stop the water isn't flowing anymore and will start to heat soak some ang get hotter. Usually the cap won't blow off unless it reaches a certain pressure but if its failed it can boil over while it heat soaks like that.

Do you know what rpm your turning on the highway?
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[THE "10" SILVERADO]

Originally Posted by INSIDIOUS '86

When you stop the water isn't flowing anymore and will start to heat soak some ang get hotter. Usually the cap won't blow off unless it reaches a certain pressure but if its failed it can boil over while it heat soaks like that.

Do you know what rpm your turning on the highway?
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2500-3100 rpms if I'm going 65-75.