V8 Radiator vs. Stock Rad Feedback

[Elbert]

also remember that a fan shroud shouldn't just be a flat part bolted to the radiator with a ring that fits the fan tacked to it. It needs to allow air to flow well from all parts and corners of the radiator.


FWIW, I am running a stock radiator (OEM style replacement from the radiator barn anyways) with a modded stock FJ60 shroud with an all stock (except for valve train) vortec with a OEM fan cluttch from a chevy truck, and an OEM fan from a chevy truck. It runs well and I have been in the desert multiple times in lots of conditions with no overheating issues. I have towed a bunch also, but nothing really over 5000lbs.

Only time temp start to climb *slightly* is in the summer when I am headed up the the Eisenhower tunnel on I-70 and I have had it floored at 5500-6000 rpm for 10 or 15 minutes to crest the top at 80mph or so. That's when I see the stock gauge climb a bit to the middle area (200-210ish) and flip on the heat for a bit. I compared my stock gauge for hundreds of miles to the output of the water temp sensor (GM) in the head using my computer while I was tuning so I feel like i know what it reads.

In town even on the hottest days with the AC running it does fine. Now hottest days here are just over 100 and the air is thinner and drier, so it may be different than your area but it si a fair test i think.. I think we had a string of 100+ days for a week or so and it never gave any issues.

Now all that being said, I think that it is basically at it's limit. It works but it is at it's limit. Otherwise it wouldn't warm up on the hard climbs up I-70.

Elbert, I bet if you made that shroud flow a little bit better it'd work a bit better.

Hey...glad to see you post up...all good info.

I've been concerend with my shroud for some time in regard to air flow across the entire core. I recognize that and hopefully we will be able to get something better soon. My truck has never overheated but I know its not running as cool / efficient as it should.

I'm going to $hitCan present shroud and my buddy is going to see what we can do in regard to setting up something like the link I posted above (same idea on OEM shrouds about flow across the core).

 

[Elbert]

maybe some of you other guys (V8-Swap) will post up pics of your radiator/cooling solutions. Details regarding what you are using (fan, fan clutch, radiator, shroud details,details on cooling issues / solutions) real temp information.

 

[phishincruisin]

I run the stock (aftermarket replacement) radiator with my swap. I use the Ford Contour fans controller by the GM PCM, through some heavy duty relays. One comes on at 200 F, the other at 204 F. I've only had my fans come on once while highway driving and that was my "test run" driving from MT, to Moab to VT. Same place as rover mentions on I-70. Its just too much fun to haul ass at 80 going up the hill headed east. You get a lot of WTF looks from other drivers.
FWIW, I wouldn't waste my time turning the heat on if I got up to 210 F, these motors can handle that temp. I goofed up and my hot wire for my relay's came disconnected so my fans wouldn't trigger on one day wheeling(totally my own fault being lazy and not replacing a crimp connector). I noticed my temp was just in the red on my stock gauge and I was reading 260 F on my Scan Gauge. Popped the hood to reconnect the fans while leaving the engine running and it cooled down to under 200 very quickly. Engine still runs fine after that little incident, and that was the only time I've thought that it would be better to have a mech fan.

 

[Elbert]

Elbert,

Thanks for the pics. As you've already said, there are a lot of variables, fan shroud obviously being one of them.

Here's what gets me, you see reports of guys running no fan shroud and cooling just fine. Based on these reports and my own experience, I'm leaning towards believing that fan shrouds help protect the user from a spinning fan (as in the case of your stock photos), but I think their benefit to overall cooling is maybe smaller than we think. A nice shroud will probably make cooling more efficient, minimizing actual fan clutch lock-up and increasing fuel economy.

In my scenario, now that I have a fan clutch that is actually locking like it's supposed to, I believe I could take off my fan shroud and undo ALL of the things I listed in my previous post that I've done over the years and I would probably still cool just fine. The affects of a properly locking fan clutch were that dramatic for me.

Just my theory based on my experiences. And I don't plan on reversing anything I've previously done.

My belief is that a shroud is critical to directing air flow across the radiator, more so when A/C is operational as that increases temps too. I believe that the shroud basically allows air to be pulled more efficiently through the device it "shrouds" ie the radiator, and thus air flows better through the radiator as opposed to flowing around or by the radiator. I also think it makes the fan more efficient...in that the fan is pulling air through the radiator more effictively as the shroud (note the GM pickup pics) ...a ducted or shrouded fan...in summary to me makes the fan more effecient and better at pulling air through or across the shrouded device (radiator) and moving air across or through the A/C condensor.

 

[Elbert]

Here is a couple pics of my set up FWIW

Looks good...did you build that yourself (shroud)?

Looks like a fixed flex fan?

I like the setback from the radiator core.

 

[Elbert]

another crazy observation: (i'm on a roll so why stop now

Notice on my GM pickup....(where there is plenty of room under the hood) you see that the radiator fan is completley captured by the fan shroud (All OEM Stock setup) and this thing cools very well... Many times I've run through the smokey mountains (I know...but its what I have close) in the summer, truck loaded, trailer plus loaded 60 and never any issue with cooling. And when the fan clutch comes on its like a tornado kicking in (which is what you want)...A/C blasting etc...nevery any issues.

Many of these other setups (mine included at present) have teh fan sitting roughly half in half out of hte fan shroud.

Anyone have any insight into a fully shrouded radiator fan vs. one that is paritcally shrouded? I don't have a 99 GM truck to post up pics from but I bet the stock GM shroud solution on the 99 is that the fan is fully shrouded. I know that some have said it is a safety thing (it may be) but I think it may be a design feature too? What you say?

 

[Toadhopper]

also remember that a fan shroud shouldn't just be a flat part bolted to the radiator with a ring that fits the fan tacked to it. It needs to allow air to flow well from all parts and corners of the radiator.

FWIW, I am running a stock radiator (OEM style replacement from the radiator barn anyways) with a modded stock FJ60 shroud with an all stock (except for valve train) vortec with a OEM fan cluttch from a chevy truck, and an OEM fan from a chevy truck. It runs well and I have been in the desert multiple times in lots of conditions with no overheating issues. I have towed a bunch also, but nothing really over 5000lbs.

Only time temp start to climb *slightly* is in the summer when I am headed up the the Eisenhower tunnel on I-70 and I have had it floored at 5500-6000 rpm for 10 or 15 minutes to crest the top at 80mph or so. That's when I see the stock gauge climb a bit to the middle area (200-210ish) and flip on the heat for a bit. I compared my stock gauge for hundreds of miles to the output of the water temp sensor (GM) in the head using my computer while I was tuning so I feel like i know what it reads.

In town even on the hottest days with the AC running it does fine. Now hottest days here are just over 100 and the air is thinner and drier, so it may be different than your area but it si a fair test i think.. I think we had a string of 100+ days for a week or so and it never gave any issues.

Now all that being said, I think that it is basically at it's limit. It works but it is at it's limit. Otherwise it wouldn't warm up on the hard climbs up I-70.

Elbert, I bet if you made that shroud flow a little bit better it'd work a bit better.

Well I can definitely say I dont have a moulded set up on my shroud which is something I need to consider making. I just took another look at the shroud and you're right, there are huge pockets (the corners) that are pretty much isolated and cut off from circulation! I took a look at your pics and it seemed like you jigsawed the pieces together to create the moulded effect. I'm not sure I have the skills to fab that and maintain the centered position of the ring. I wonder if there is a GM fan shroud that has the right fit, taper and offset? I'm guessing NO since you'd probably have used it if it were available.

 

[Kurtis]

I have a 350 tbi, the stock radiator, A/C, oil cooler, transmission cooler. I run a truck fan clutch and truck fan with a shroud. I also live in Arizona so it is the most extreme test possible. The truck runs great around town, on the highway etc. With the stock radiator it will heat up when idling. I'll let it heat up and it will never go past 230 on my mechanical gauge. It typically runs right around 195-205 with the stock thermostat and normal driving.

From my experience as well a/c and no a/c is night and day in terms of stress on the cooling system. If you don't have a/c you really have no idea of how close you are to your cooling capacity. Without the a/c on the truck will run at 195 in 117 degree heat idling, pulling grades or offroading.
I am going to switch to an aluminum radiator next time. I am also going to get the 62 version with the built in transmission cooler as I feel that I just plain have to much stuff up front. I also have a pusher fan for the A/C when it comes on witch really helps the temps.

I have a question for you guys though, I honestly can not tell that my fan is ever engaging. It pulls air but I am used to my 06 2500hd which sounds like the truck is getting ready for liftoff when it kicks in. At 230 I would defiantly assume the fan would be running... I have never overheated and put well over 20k on my swap with no issue and plenty of runs up the mountains fully loaded. When your 5.7 fans kick in how loud is it? It seems as if it is engaged but the difference is hardly noticeable to me.

Do you have any luck with a specific fan clutch on your 5.7 motors? I thought I bought the hd version for a 1993 suburban when I did my swap 3 years ago but I don't really remember anymore. I was tempted to throw a flex-lite fan on for a second to see what was going on.

 

[Toadhopper]

I have a 350 tbi, the stock radiator, A/C, oil cooler, transmission cooler. I run a truck fan clutch and truck fan with a shroud. I also live in Arizona so it is the most extreme test possible. The truck runs great around town, on the highway etc. With the stock radiator it will heat up when idling. I'll let it heat up and it will never go past 230 on my mechanical gauge. It typically runs right around 195-205 with the stock thermostat and normal driving.

From my experience as well a/c and no a/c is night and day in terms of stress on the cooling system. If you don't have a/c you really have no idea of how close you are to your cooling capacity. Without the a/c on the truck will run at 195 in 117 degree heat idling, pulling grades or offroading.
I am going to switch to an aluminum radiator next time. I am also going to get the 62 version with the built in transmission cooler as I feel that I just plain have to much stuff up front. I also have a pusher fan for the A/C when it comes on witch really helps the temps.

I have a question for you guys though, I honestly can not tell that my fan is ever engaging. It pulls air but I am used to my 06 2500hd which sounds like the truck is getting ready for liftoff when it kicks in. At 230 I would defiantly assume the fan would be running... I have never overheated and put well over 20k on my swap with no issue and plenty of runs up the mountains fully loaded. When your 5.7 fans kick in how loud is it? It seems as if it is engaged but the difference is hardly noticeable to me.

Do you have any luck with a specific fan clutch on your 5.7 motors? I thought I bought the hd version for a 1993 suburban when I did my swap 3 years ago but I don't really remember anymore. I was tempted to throw a flex-lite fan on for a second to see what was going on.

Hey Kurtis,
As I mentioned I'm running the Hayes HD fan clutch and it never seems to change. Its ALWAYS stiff and never freespins so I think its the wrong one to run.
I know the OEM ones are supposed to be the longest lasting and most accurate, but as mentioned earlier the distance the clutch is from the rad had alot to do with whether/when it engages. Ebert mentioned the clutch is about 5 inches from the rad on his chevy truck, but I bet its different for different models. I know what you mean about the AC stressing the cooling system, so I really want to get a handle on mine before I re-hook up my AC. Id also like to hear what people are running. What make/ model did your sroud come off of? Does it fit well?

 

[Elbert]

Agree please post up if you have a/c functional and condensor in front of the radiator.

FYI when my fan clutch engages on my 60, you can certainly hear it, its a 5.7 vortec, not as loud as my 6.0 pickup but certainly noticeable.

Sent by a DROID

 

[rover67]

My ac is functional and condenser is in front of the rad. When the fan clutch kicks in full force it sounds like it could suck a small child through the front grill..... Usually that docent happen unless I've been stationary for a while in pretty decent heat.

The shroud wasn't too hard to make. I cut away the Fj60 shroud until it slid in, the stuck a sharpie on the fan blade.... Spun it and had a trace of where I needed the ring. Fab the ring, tack it in, then fill in the gaps with patches.

 

[rover67]

Also as mentioned above... My motor starts to get too hot around 250-260. It has been there a few times due to electrical issues with the old countour fans is the only way I know. And by too hot I mean starting to miss and not run. Somehow no hg issues ( per religious oil analysis) so I assume all is well.

I know switching heat on at 210 is conservative, but I do it anyways.

And Elbert, nice to see ya to man, been com in here a bit less frequently lately.

Also, as another FYI my swap has 100k miles on it. Probably 50k with the mechanical fan?

 

[mmuthart]

Hey Kurtis,
As I mentioned I'm running the Hayes HD fan clutch and it never seems to change. Its ALWAYS stiff and never freespins so I think its the wrong one to run.
I know the OEM ones are supposed to be the longest lasting and most accurate, but as mentioned earlier the distance the clutch is from the rad had alot to do with whether/when it engages. Ebert mentioned the clutch is about 5 inches from the rad on his chevy truck, but I bet its different for different models. I know what you mean about the AC stressing the cooling system, so I really want to get a handle on mine before I re-hook up my AC. Id also like to hear what people are running. What make/ model did your sroud come off of? Does it fit well?

Toadhopper,

The fan clutch shouldn't spin freely. If it did, it would indicate it lost it's hydraulic fluid.

The fact that you've never heard the 'whoosh' may be your problem and is exactly what I was missing for 10 years! Dependingn on your level of sound proofing, it may be more or less noticiable. But if you get in a high temp situation and are listening for it, you should hear, it's loud.

 

[Toadhopper]

Toadhopper,

The fan clutch shouldn't spin freely. If it did, it would indicate it lost it's hydraulic fluid.

The fact that you've never heard the 'whoosh' may be your problem and is exactly what I was missing for 10 years! Dependingn on your level of sound proofing, it may be more or less noticiable. But if you get in a high temp situation and are listening for it, you should hear, it's loud.

Yea, But the fan wont even spin a quarter turn when completely cold. Is that normal? I've heard you should get a half turn at cold, but let me know your thoughts.

 

[Toadhopper]

My ac is functional and condenser is in front of the rad. When the fan clutch kicks in full force it sounds like it could suck a small child through the front grill..... Usually that docent happen unless I've been stationary for a while in pretty decent heat.

The shroud wasn't too hard to make. I cut away the Fj60 shroud until it slid in, the stuck a sharpie on the fan blade.... Spun it and had a trace of where I needed the ring. Fab the ring, tack it in, then fill in the gaps with patches.

Nice low tech technique! I have the ring and the base of the FJ60 shroud so I think I'll separate the two tack the ring and try your patching technique until I get the taper I'm looking for. I'd really like to get the OEM fan clutch, aluminum radiator, 12 blade Cadillac fan blade, and OEM H2O pump in there all at once and just use the "kill every bird" approach!
Bryan

 

[spotcruiser]

This is what I did for cooling of the '96 5.7l in my 40. It runs between 195F (where the thermo begins to open) and 204.9F at 70 on the highway in 4th gear (it runs at 199F at 70 in 5th gear). It's a Griffin 19x22 rad (I couldn't really go larger without causing other issues), stock '96 fan clutch with a later-model 11-blade nylon fan, and a homemade fiberglass shroud. I had a local guy weld the aluminum flanges on the tanks of the rad for mounting of the shroud to the rad and mounting of the rad to the frame. It all works great. With a 60-series, you should be able to use a wider radiator and get more airflow around the engine, so better overall cooling. It's pretty tight in the 40.

 

[spotcruiser]

Just a couple of pics showing the shroud construction. The method was similar to what you see in the hot rod forums, but a friend showed me his technique using two pieces of particle board with the correct holes sawed in them, spaced for the offset between the fan center and the radiator core, and then spaced for the desired depth of the shroud. It's a little messy to build (mostly dust during sanding), but it's not difficult, and the results can't be argued with.

 

[spotcruiser]

Few more.

 

[Toadhopper]

Wholly Custom Craftsmanship Batman!

 

[Elbert]

Yea, But the fan wont even spin a quarter turn when completely cold. Is that normal? I've heard you should get a half turn at cold, but let me know your thoughts.

Don't think you said what type of fan and fan clutch you have.

The normal way in which a GM fan clutch works is that when cold (engine off) the fan would spin with some minor resistance. When fully warmed up the (engine off) fan should be fairly hard to turn by hand.