Frankenstein 454 swap. Overheating at idle.

[83Burban]

Just a guess but, it sounds like your fans aren't moving enough air through the radiator to me.

I don't really know how to tell. It seems like they are pulling pretty hard. Its a nearly brand new 3 row aluminium. The gap between the shroud and the fans is minimal. Should I try to fill the space with backer rod?

 

[83Burban]

I've got a coolant over flow bottle on the way, the bottle on the truck is more home made nonsense. Had a drain **** on the very bottom...that was shut...smh, opening it will just have it pissing coolant all over the place. Idk how detrimental this might be, but I know it's not right.

Just changed the radiator cap. I don't know what psi the cap the new rad came with, there are no markings. But I just put a 16psi duralast cap with pressure release valve on it.

I got a new temp switch....im pretty positive the one in it is functioning properly...but they are cheap and easy to change, so why not?

And just my luck, its snowing in Kansas City. And my blower motor or relay just took a dump on me.

 

[83Burban]

Going to double check the electric fans. Make sure they are, in fact, pulling air. There's certainly not air being blown out the grill. But I guess one of them might have the blades backwords?

Im also going to take some aluminium tape to the vents in the shroud. As well as tape off the small gap all the way around the shroud. Make sure that ALL the air is, in fact, being pulled through the rad.

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[QBuff02]

That is a good point to make sure both your fans are configured to "pull" air through the radiator. Hit a deer one time in an older car with a dual fan setup. Front of car completely destroyed, think- barely any braking before impact at 60mph with 130lb deer.. Got the car back from the body shop a month later and the a/c just wasn't working for **** at lower speeds and around town, so I hooked my a/c gauges up figuring it was low on charge and by the gauges the a/c system was spot on. Just so happens that I dropped one of the caps for the valves in front of the car while it was running and when I bent down to pick it up I felt hot air hitting my face. come to find out the Body shop wired one of the new fans up backwards so I had a puller and a pusher! Re-pinned the two wires to the one that was pushing air back out through the grill and problems immediately went away.

 

[Bextreme04]

Couple things.... 210 isn't really overheating, its the normal operating temp for a Gen V, Gen VI. It should be lower with the radiator and thermostat you are running though. With all the other nonsense cobbled together crap that is going on with that motor, I wonder if you have Mark IV heads on a Gen V block and they used the wrong headgaskets? It is a common issue for there to be major overheating issues when this is done. There are specific special headgaskets that have to be used when you do that. What is the block casting number and cylinder head casting numbers? Also, those electric fans are tiny and that shroud is not very good either. The factory GMT-800 fans for a small block are way bigger than that and the big block radiator is also much bigger than that.

 

[83Burban]

Ive done a lot of crawling around looking for numbers of any kind and have come up with squat. Im going to get it out of the snow this afternoon to work on it and I'll do some more checking. I'll bust out the Degreaser and a brush if needs be. But its really not all that dirty. I know the block numbers are supposed to be by the bell housing. But all ive found says 7.4

It does not stay at 210. Was just passed 220 and climbing when I shut it down last night.

As far as the radiator goes, the shroud / rad were sold together as one unit. But should be easy enough to fit a different shroud. Based on some lite research, I was under the impression that aluminum radiators are much more efficient than their copper predecessors. It cost a pretty penny, but I know that looks and $$$ does not allways mean its actually quality. Seems really well built compared to the plastic stuff I pulled out of it.

It was supposedly for a BBC, And designed to handle high output engines. It fits the mounts properly. Were it any wider, it would reach out passed the grill and would not really have access to air, or at least thats how it seems... but ive been very wrong before.

It's 33.5" x 20", three core, solid aluminum. Fans are 12" 12v- 80w. Seems to be flowing coolant properly. Both blades are in the same orientation and seem to be pulling.

Looking for different shroud options.

 

[83Burban]

Ive wondered about incorrect gaskets. But she really seems to run well. Temps stay at 185 constant when running down the hwy. Even at like 35mph she stays cool.

I would imagine my over heating would be worse at speed if gaskets were the issue?

 

[83Burban]

Lol I'm learning lessons the hard way, guys. Thanks for being patient. Hopefully some other wayword soul will benifit from my struggle.

 

[Bextreme04]

Ive done a lot of crawling around looking for numbers of any kind and have come up with squat. Im going to get it out of the snow this afternoon to work on it and I'll do some more checking. I'll bust out the Degreaser and a brush if needs be. But its really not all that dirty. I know the block numbers are supposed to be by the bell housing. But all ive found says 7.4

It does not stay at 210. Was just passed 220 and climbing when I shut it down last night.

As far as the radiator goes, the shroud / rad were sold together as one unit. But should be easy enough to fit a different shroud. Based on some lite research, I was under the impression that aluminum radiators are much more efficient than their copper predecessors. It cost a pretty penny, but I know that looks and $$$ does not allways mean its actually quality. Seems really well built compared to the plastic stuff I pulled out of it.

It was supposedly for a BBC, And designed to handle high output engines. It fits the mounts properly. Were it any wider, it would reach out passed the grill and would not really have access to air, or at least thats how it seems... but ive been very wrong before.

It's 33.5" x 20", three core, solid aluminum. Fans are 12" 12v- 80w. Seems to be flowing coolant properly. Both blades are in the same orientation and seem to be pulling.

Looking for different shroud options.

Aluminum is not more efficient than copper/brass. They are lighter, and cheaper... and the more efficient design of the internal passages in the core(turbulators) make them almost as efficient as the older radiators. Race cars don't use the aluminum radiators because they are more efficient, they use them for weight reduction and because they don't need the higher heat dissipation due to them never really operating in the low air flow environments that you are now having issues with.

The stock aluminum big block radiator for a GMT 400 is a 34"x20" core with plastic tanks adding another 4-6" to the width. The stock fan for that motor is a 9-blade reverse flow 19" fan that flows WAY more air than those electrics you have. I think you had a combination of poor coolant flow from the wrong pump and a poor airflow condition from the shroud/fans you are using. 80watts is pathetic amount of airflow.... a large mechanical fan like the stock big block fans can consume up to 40hp. Horsepower has a direct conversion to wattage since they are both measures of power. 1hp = 745watts... so the factory big block fan can consume as much as 29,800 watts. You are pushing 160watts worth of airflow with those dinky fans. Its not a direct correlation because fans are most effective at a specific RPM and the electrics will be ALWAYS at peak efficiency where-as the mechanical is almost NEVER at peak efficiency, but still... you need more powerful fans to keep it cool at idle.

The block casting number for a 5th or 6th Gen BBC will be on the top of the passenger side rear of the bell housing. Head casting number will be under the valve covers. Original engine application stamping will be on a flat machined surface either centered above the timing cover or in front of the passenger side head.

 

[Bextreme04]

Hit the two circled spots with brake cleaner and a wire brush... you should see a stamped number in one of those spots that will give you the original engine application.

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[83Burban]

Thanks for all the knowledge. I went ahead and added the plastic shroud back on. Had to be trimmed to fit. Then, I taped up the vents in the face of the shroud. Once it dries out im going to tape up the 1/4" gap on the bottom. Truck never got over 210. But the high today is about 45°

Looking for some better fans. Found some that are 120w and should bolt right on.

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[Bextreme04]

Just for reference on fan and radiator size. Here’s the stock GMT-400 454 radiator that will be going in mine along with a stock 2011 Silverado 2500 electric fan setup on it. The fan CORE is 34”x19” and as thick as my stock 4-core brass radiator. Each fan has its own 30-amp relay.

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[Bextreme04]

The fans are about 15" each. @Catbox has some SPAL electric fans on his BBC and no issues I believe. Maybe he has something to add?

 

[Catbox]

I did have a set of Flex A Lite fans on my 454.
We were having some kind of weird feedback issue with the fans that was killing alternators.
After 3 alternators, we ended up reinstalling the stock fan and shroud a couple months ago.
I even bought their own specific $160 digital fan controller, still killed the alternator.

But, when it was working it never had an issue.
The fans are 12 inch fans and move tons of air when they are on.
Idling in the driveway, rock steady.
70 down the freeway, same.

 

[83Burban]

Im running a "painless" wiring harness for the fans. This truck has a dual bat set up and I think an over sized alt due to having front and rear AC. But I may be wrong.

Looking at replacement fans....most seem to be labled in amps, not wats. Amps x volts = wats correct? Ive found some fans that are supposed to be 1455cfm at 13.5amp. If that conversion is correct they would be 160ish watt fans, correct?