For those real "cool" cats: What's your recipe?
 

There are those here whose cooling system is aces. Their cars never get off the thermostat, or they can idle in a drive thru for an hour with the AC on, in 110 degree heat.

I was wondering if anyone with these highly successful cooling systems would be able to share their formula with common criteria. Maybe even include stats on performance in various ambient temps. Looking to see what WORKS.;)

Platform (year and model):

Engine (mild to wild):

Water pump config (8 bolt, 11 bolt):

Water pump style (cast impeller, stamped impeller, special aftermarket):

Water pump pulley size (small/med/large diameter):

Lower hose spring:

Radiator (# rows, material, brand):

Tstat:

Cooling fan configuration (blades, clutch specs, electric, etc.):

Typical use factors, like ambient temp, AC, etc.:

Any special mods:


So I'll get the party started with the template, even tho I wouldn't consider my setup an example of highly successful. In fact, mine needs some help.

Platform (year and model): 1967 Firebird

Engine (mild to wild): mild 350P, I would put it at a 2 out of 4. Hotter than stock. FiTech.

Water pump config (8 bolt, 11 bolt): 11 bolt

Water pump style (cast impeller, stamped impeller, special aftermarket): Factory style cast

Water pump pulley size (small/med/large diameter): Small diameter

Lower hose spring: No, but have one arriving this week!

Radiator (# rows, material, brand): 4 core Champion, aluminum.

Tstat: 180

Cooling fan configuration (blades, clutch specs, electric, etc.): 19" GM, Hayden 2797 clutch

Typical use factors, like ambient temp, AC, etc.: Super hot summers. Car has AC, but is not used currently. Temps creep at idle, temps creep while cruising.

Any special mods: divider plate clearanced.

No secret formula here but scirrotica solved all my idle temp woes with this cheap flex fan:

https://www.summitracing.com/parts/DER-17019

Will keep that in mind. I have a factory shroud, good fan depth. Maybe the system is fully coated with scum, or my divider plate rotted away unknowingly. I've always kept a good antifreeze mix. I have baffles between the bumper and core support to keep air going into the radiator. I can't imagine my open RA hood scoop inserts are drastically interrupting under hood air flow much.

It's not that mine DOESN'T work, but it definitely underperforms.

I'm hoping some others chime in with their cool setups.

One sage here told me that if the temp goes up when it's idling then it's the fan/airflow.

My old non-stock fan was too small and didn't push enough air.

How far does your stock fan stick out of the shroud? Or does it?

Water pump divider has to be set, I didn’t do mine, a guy in Miami did it, I never overheat now. I use a 160 thermo too. I can have ac on in Dreamcruise, no issues.
Test your rad cap, even if it’s new. We tested 3-4 new ones at the natz last year, they didn’t hold rite out of the box.

cooling
 

ok throw my 2 cents in on this topic

My cars setup is as follows.

-11 bolt waterpump with tight clearance to divider plates

-Cold Case aluminum radiator with TH400 cooling lines in use in rad
.
-all factory baffles to direct air into radiator and seal around core support

-original fan shroud my car was born with

-converted to AC pulley for crank and waterpump to speed up water pump and fan

-factory AC 7 blade fan from 76TA using a hayden STD duty fanclutch

-NOS AC Delco 170 degree thermostat. verified to crack open 165 and fully open 180.

-Q-jet 7028276 with proper recalibration done during rebuild and full RA pan setup

-factory HEI with 12 initial 32 total using heavy advance springs for conservative curve.
weird thing is my car idles butter smooth and has more toque off the line with slower
curve. also 12 degrees from VAC ADV and have tried both ported and FMV and neither
effected cooling. but I prefer exhaust note from FMV at idle(today anyway).

-with 3:08 on highway she is happy at 75 and runs just shy of 180 and then drops back down to 170 on backroads. never hear fan clutch engage and happy with cooling.

In my garage for wall art, are the original crank and WP pulleys and 5 blade. they worked
well for years but temp did creep up in traffic. All these changes occurred over 15 years.
biggest bang for my buck was to speed up WP but then factory 5 blade fan was too loud on
highway. thus, installed matching fan clutch and shortly after has to replace leaking radiator and Cold Case was installed. Gas mileage did improve with fan clutch change.

this is just what worked in my car. I have a collection of thermostats that worked and some that were crap. current Delco stat was installed with no additional holes or voodoo.
All original parts were saved if I ever wanted to go back to original setup.

Gerry

Clearanced 11 bolt pump, Shroud, clutch fan, Cold Case radiator, 180 degree thermostat, 12 degrees BTDC, manifold vacuum.

George

I'm glad that helped you out, I started using those composite fans in the late 70s and they have always been affordable to buy, and do away with all the extra weight, and mass hanging on the extreme end of the water pump shaft. If the car starts to get hot in an idling situation that fan will pull enough air if you rev it in neutral to bring the coolant back down quickly.

If you keep the basic principles of physics in mind and science out cooling system problems you can pinpoint and fix your woes.

Plenty of air through the radiator, no restrictions in the system and as much volume of coolant as possible in the system. Overdrive the pump to keep pressure high to minimize steam pockets and run the coolant as fast as possible through the system.

Thermostat, or a restrictor need to be in the system to keep water pressure high in the engine. Coolant rejects or takes on heat at the speed of electricity, so the old wives tale that you can run coolant too fast through a system is false.

GM had cooling woes in their 6.5 turbo diesels, one of the changes they made was to run a water crossover with dual thermostats converging into a single upper radiator hose. The purpose was to allow more volume of coolant through the engine and radiator. With 2 thermostats the flow was higher, but still had a restriction to keep water pressure in the engine high. Water pump was modified to pass a higher volume of coolant and the increased the size of the fan as well as reprogrammed the fan clutch to come in sooner at a lower temperature.

If you're running and automatic transmission. and you're borderline on overheating don't use the cooler in the radiator, use a separate cooler.

Keeping a dirt track Pontiac cool during the summer running for 20 laps in the features made me find answers to why they overheated, and what measures I could use to eliminate the O/H problems. Lots of experimenting and research went into the cooling system, at the end I could run 20 laps and never get the coolant above 180, no matter what the ambient temp was.

I hope this helps someone having cooling system problems..........:thumbup:

Good point.

Personally, I run out of the trans, to external cooler, to radiator cooler, and back to trans. I've always reasoned that the external pre-cooler took load off the radiator, and if anything, the radiator could even add excess heat back IN to the trans fluid to get it to normal fluid temp in case it was cold outside.

I think I have the opposite problem of most posters, over cooled in town and under cooled on the highway. With a 180 degree thermostat, I barely see 165 in town or at steady idle. Running the A/C will get it up to 180.

At 70 mph though, it's running at 210 and will run 230 with the A/C.

1700 miles on Len Williams built engine. Original 1970 350 block stroked to 413, XE276HR cam, Torker-I intake and 800cfm Q-Jet, 6X-4 heads, 9.3 cr

TCI Turbo 350 with 2400rpm stall converter, 3.23 rear axle

Original 4 row radiator, has been "overhauled" twice with lower row replacements. Internal Turbo 350 transmission cooler used. 24 quart cooling capacity

Edelbrock 11 bolt water pump with CNC impeller

Original 7 blade fan with new Hayden H-duty clutch

CVF serpentine belt drive - appears to be at least a 10% overdrive from the crank pulley to the water pump pulley

14 degrees initial timing, 21 mechanical all in at 3200 rpm, MSD 8563 distributor vacuum advance connected

I'm beginning to think the radiator has been painted too heavily and can't dissipate heat fast enough at higher engine rpms.

1979 Trans Am W72 400/4-Speed; stock low-comp 400 with a mild camshaft and true dual exhaust; everything else more-or-less stock. I'm running an 11-bolt Flowkooler clearanced down to 0.050" w/ gasket; Oversized 1.25" 2-Row Cold case radiator; new copper/brass heater core; 160 degree thermostat (balanced sleeve type); all new hoses and lines with anti-collapse spring in lower hose; 15 PSI rad cap as original; stock fan shroud; stock 7-blade 10008888 19" clutch fan; Hayden #2747 heavy duty clutch; shroud sealed to radiator with weatherstripping; all factory baffles and seals in place; stock overdriven AC waterpump pulley; stock HEI with 18 degrees initial timing as per factory spec; vacuum advance metered through the factory modulator valve that supplies partial manifold vacuum to the distributor (around 17 degrees of the full 25 degrees the advance canister supplies), and so I'm making 35 degrees total advance to the distributor at idle. Mechanical advance around 34-35 BTDC by 3500 RPM. Cooling system jackets clean as far as I can tell, since every flush I've done has never revealed dirty coolant - it always comes out green. I use Napa 50/50 pre-mixed conventional green coolant and every couple years as part of a backflush and refill, I throw in a bottle of Rislone Super Coolant additive, cuz why not?

I live in SoFlo, and around town, my car struggles to reach operating temp and I can idle till' the cows come home and the needle will almost never reach that first tick on the temp gauge (which for 2nd gens, I've always interpreted as around 160 degrees), no matter the ambient temp. I can drive around town for an hour and literally grip my hand around the radiator hose and hold it without getting burnt while the car is running.

My temp will creep up to the first tick, maybe a little past it when I'm on the highway sustaining higher RPMs, and that's after roughly 10-15 minutes on the highway. I've never been on the highway long enough to see how high the engine temp will go since I have a driveline vibration above 60 MPH that I need to address, so I usually avoid taking the highway, anyway. I have the factory 3.23 gears, and so in 4th gear on the highway, I'm at around 2250 RPM at 55 MPH, so figure around 2800 RPM at 70 MPH.

The AC, however, will cause my engine temp to spike very quickly. I think something may be wrong with my compressor or AC system, because while it does blow cold air, it taxes the engine a lot and just sitting there idling, I've seen the temp needle creep to halfway between the first tick and 220 tick on the gauge within maybe 8 minutes before I freaked out and shut off the AC. It's been converted to R134A, but only had the lines and compressor replaced with a crappy reman unit, while the condenser and evap are still the originals. I usually drive the car in the evenings, so I don't use the AC.

Overall, I'm pretty happy with the performance of my cooling system for living in SoFlo. Leagues better than when I first got the car, even though even then, it has never overheated. I just wish I could more confidently use the air conditioning, since living in SoFlo without it is oppressive and you need to make a lot of concessions to be able to enjoy the car without it (i.e. driving it only at certain times of the day when it's not as hot out, or depending on what time of the year it is).

I also think that people's standards for how these cooling systems operate are a little high, especially in accordance to the factory specifications as shown in service and owner's manuals. People get awfully paranoid just seeing their car in the 190's-200's, when in reality those are totally normal operating temps which these cars regularly saw when new. So many of these overheating threads may not even be based in actual overheating, but rather, "car not running at a temp that I, the owner, personally like to see it at."

I appreciate all the posts.

Yesterday I was out driving my 67 FB. It was 100 out.

Average temps while cruising at 45-50 mph were 195-200. Idling would get a little hotter. I did see 215 in a drive thru. This was without running ac.

In a conversation with a fellow 1st Gen enthusiast locally, we talked about maybe this is as good as it gets, but I don't want to accept that yet.

2nd gens have bigger radiators, so that might give them the better cooling nod there. And maybe the air flow through the nose/grill/cowl is also better.

I get tripped out occasionally that the 5.3 in my 04 GMC can be cooked by a skinny radiator, 5" wider than my bird, with plastic tanks.:confused:

Keep those recipes coming!

That's the heat transfer difference between unpainted aluminum and painted copper/brass.

Finally stole a moment to try something. In searching for a tstat, I saw a number of standard vs deluxe stats, and some listed as high flow. Since I had planned on swapping perhaps to a 160, I wanted to see if 160 was even possible. So I pulled the thermostat, and went without one. I buttoned it up and went for a drive in wonderful 67 degree night air, not many more of those left.

Previous night drives have given me 185-188 while doing 45-50 mph at 2500 rpm. Highway jaunts might poke it up a few degrees while buzzing at 3500 rpm. Idle at a light causes a few degrees more creep.

This drive took a long time to heat up, as expected. It took at least a few miles, including highway, to crack 160. After several more miles of town cruising at 45-50, my steady state temp ended up around 171. After the drive, I let it sit at idle for several minutes. It crept up, and reached 195 before I decided to call it a night.

My hypothesis? I'm thinking that my basic 180 tstat was providing a flow restriction that did not allow full cooling ability. Having no tstat gave an extra 15+ degrees of extra cooling for similar driving conditions.

The idle creep still bothers me. It makes me think airflow issue. I have a few other fan combos laying around for further troubleshooting, including a six blade flex fan.

Next step will be lower radiator hose/spring, with system flush, then another data set.

The issue is, that restriction the thermostat provides allows for pressure buildup in the system to further protect from boiling the coolant in the event that you do start to run hot. Maybe try a balanced sleeve thermostat (the "hi-flow" ones you're seeing).

Also, what's your tune? Initial timing, are you using vacuum advance and if so, manifold or port vacuum to the distributor? Airflow is indeed the most important factor for idle temps, but ignition timing plays a big role, too.

I'd bet if you put one of these on your low RPM creep will disappear:

https://i.ibb.co/VvJhQzS/ALL30094-02158.jpg

These are called RV fans, and are intended to move a ton of air at low engine speeds, they do just exactly that. At idle you can feel how strong the suction is in front of the radiator by standing there.

My radiator shop guy showed me with cigarette smoke how little air the clutch fan was moving at idle. At that time in the late 70s the fans were under $20, so I said I'm going to try one. It one of the best cooling moves I ever made. The prices have doubled since then, $29.99 but still a good buy. The largest they make is 18 inch, but it still works better than any 19/19.5 fan I've tried.

https://www.summitracing.com/parts/aaf-all30095

The difference between this fan, and a conventional fan is the almost 90 degree pitch on the fan blades, that's what allows it's ability to move air at low RPM.

14 initial, running somewhere around 12 degrees manifold vacuum advance. It likes a little more, but I wanted to be reasonable with the rest of the tune. I am a fan of manifold vacuum advance for the idle performance.

I read about your fan suggestion to King Buzzo in an earlier post, and it had my attention. Yeah, needs more air. Can't really beat the price.

Any input on the durability of that fan? Any thoughts on whether to hard mount on a spacer, or mount on a clutch? Thanks!

You hard mount to a spacer, no clutch involved. Another bonus is dropping a lot of weight off of the end of the water pump shaft. The extra load from the severe pitched blades would likely make a clutch slip so direct drive like the factory did for decades.

I've run them on my dirt cars for 3 seasons at about a 5500-5800 RPM redline. After I took the fan off of the race car I put it on my 1973 T/A street car and it was on that car (5-6 years).

I borrowed it for an enduro car, the front end got crunched and the fan hit the radiator and the blades broke. The amazing thing is the plastic blades did very little damage to the radiator, unlike a metal fan blade does. I was able to solder 2 tubes up on that radiator and kept using it. I can't think of any downside to substituting a composite fan for the heavy metal clutch fan.

For $30 and some spacers and bolts, it's hard not to justify at least trying one......;)

I bot a spacer with my new fan but didn't end up using it as it lined up nice on my 2nd gen...measure twice

Nylon fan and a 1" spacer are on the way.

Looking around my junk today. Found a little used 19" 7 blade fan from a 75 Chevy truck mounted on a fairly tight clutch. I might try that too for more comparison data. It's only 4 bolts and some bloody knuckles, right?

I've chased cooling issues on my '67 Firebird over the years and have spent lots of money on fans, radiators, snake oil coolant, etc... and what I've learned boils down to this:

Large clutch fan & shroud* > SPAL electric fans > any chicom electric fan.
*(Although modern PWM brushless fans have pretty much caught up and may be the best choice)

Straight water is the best coolant, but you need an additive to prevent corrosion & lube the water pump.

The faster the water can flow, the better it will cool. I.e. No thermostat > thermostat > restrictor.
(The science behind it: heat transfer coefficient)

Here's a post I made a while back on cooling with a little more detail.

The Ultimate Cooling Thread

2nd only to general cobbling, which is a problem on all old cars, I think the biggest problems is almost all of the 60s/early 70s era cars are under radiated from a size perspective. Which is why cooling is often an issue.

Per Cold Case a first gen F-body "Big Block" radiator has core measurements of 16.85 x 23 for a total frontal area of 387.55.

By comparison your basic run of the mill 5.3 99-2012 Silverado radiator from Cold Case is 17.25 x34 for a total area of 586.5 inches. By percentage of change, that's 51%

Thats a giant difference. And its reflective of sizes available for most of those common 60s cars. We talk about all the fan solutions etc, but if you just have more cooling area its going to solve most of your problems. Unfortuately that's easier said than done.

I disagree that a big clutch fan is the best solution. And I say that as someone who runs that setup. A well engineered electric fan setup is better. There really isn't an argument. Most peoples cooling issues with old cars are at idle and that's where the electric shines because its not RPM dependant. Plus less parasitic loss ETC.

Now I do agree that if we were to graph this out, the big clutch fan would probably be the equilibrium point where ease/value meets an effectiveness line. So I would also recommend the setup to most people, but I don't think the statement that it is the best is correct.

Many things factor into cooling system efficiency, and not everything that solves one persons problem will necessarily solve someone else's problem. All the pieces have to be put together to form a system.

The first gen birds do have a limited frontal area same as the 67 GTOs did. In 68 GM widened the frame horn area to allow a larger frontal area for the radiator on A bodies, but F bodies didn't get a redesigned subframe until 70.

The narrow crossflow radiator did one other thing beside have vastly smaller frontal area, the small radiator also reduced the cooling system capacity. One of the things I learned when trying to make my oval track cars run cooler is additional capacity also helps. Ford used to use the reservoir expansion tanks in their systems as it added more capacity to the system.

GM/Detroit diesel 6.5 engines had problems with O/H usually pulling a load on long grades. Lots of warranty dollars got spent by GM because of the marginal cooling systems in those trucks.

The engineers made several modifications to the later truck engines to address the marginal cooling systems. Redesign the clutch fan to come on at a lower temp, and lock up more positively. A water pump impeller redesign to deliver approximately 40% more coolant, dubbed the HO pump. In conjunction with the water pump improvement they made a dual thermostat water crossover to allow the redesigned pump to not be restricted at the thermostat housing. These changes made a lot of difference in the cooling efficiency. Many of those changes on the 6.5 carried over to the 6.6 Dura-Max engines.

Picture of dual thermostat 6.5 water crossover:

https://i.ibb.co/wVKqb5K/dual-thermostat-6-5.webp

Another thing is the whole cooling system in these 50 plus YO engines and cars have crud and sediment in them, that may or may not get addressed during restorations. Some of these cars are still using the OEM engines the car was built with. Lots of variables in every car/engine combination.

Chrysler had their K cars with 1.7 VW engines in them with a iron block, an aluminum cylinder head, and a brass radiator. Back in the 70s the cars would O/H on the highway due to the corrosion combination of these 3 metals in the cooling systems the radiators would scale on the inside effectively insulating the heat rejection of the radiator. It took place in under 5 years and around 40,000 miles.

Lots of old wives tales on the physics of how an engine cooling system works add to confusion when troubleshooting cooling system problems.

Lots of things that most people haven't a clue about that take place under the right conditions in older cars, any combination of some of these things can make you tear your hair out trying to solve an O/H problem.

:2cents:

HaHa! My Sierra had a 28" wide core, which was MOSTLY adequate, until I went to a 34" HD sized core. It's a 2004. In 2005 GM went to a dual electric and never turned back. Hmm....

You hit the nail on the head!
From my experience with a Firebird, the radiator is way too small for a high performance engine. So when the cooling area is reduced, the only cure is to increase the airflow across that area since we're somewhat limited on what we can do to increase the coolant flow through the radiator.

When I say that a clutch fan is better, I'm referring to the ability to move a lot of air through the radiator. A good fan/clutch/shroud combo will move way more air than most* electric fans. ....Except at idle. This is where an electric fan, set up as a pusher, can help keep the temps down at idle.

You are correct when you say "A well engineered electric fan setup is better." but I would add, "When combined with an adequately sized cooling system", which, we don't have.

The other problem with electric fans is the fact that the manufacturers LIE. And people (generally) are going to buy the fan with the biggest CFM rating for the least amount of money that they can find. The problem is that most of these sellers just pick a random cfm number and have never actually tested the fan. I've seen the exact same, made in china, fan advertised as 2400 cfm all the way up to 3800 cfm, but it only draws 7 amps. I call BS. In reality, it's probably a 240 to 380 cfm fan once mounted to a radiator.

When I bought a Cold Case radiator for my bird, I also bought their 16" electric fan/shroud combo that was rated at 2500 CFM, but only pulls 6.85 amps. :rolleyes: My car overheated before I left the yard.

Cold Case does make the best radiator that I have tested and their warranty/customer support is excellent, but they should add Spal fans to their inventory because the ones they sell now are junk.
SPAL is the only company that I'm aware of that publishes the actual flow ratings at different pressure drops and it's surprising at how much that cfm number plummets when pulling through a radiator.

Now I'm nowhere near being an expert on cooling systems, but I have tried multiple fans, shrouds, & radiators in my bird and these are the things that have worked, or not worked, for me. YMMV.

* Newer OEM, brushless, PWM, fans (Made by Spal btw) are close enough to pulling as much air through a radiator as a clutch fan that I would need to see actual test results to decide which one is better.

I have a 19" Camaro/Cadillac 850 watt PWM fan in my bird now and it does a pretty good job of keeping the IA2 cool; especially at idle. My temps climb when cruising, but when I pull up to a stop light, I can watch the temp drop from 210* +/- to 185* in less than a minute. It sounds like a turbo prop preparing for takeoff, but it does get the job done. The downside is it's not a direct fit so I had to fabricate a bit to make it work. It's expensive and requires a PWM controller. It can pull a steady 70 amps so a quality electrical system is a must.

A clutch fan & shroud did as good, or better, at cooling (for a lot less $$$), but big fans & serpentine systems DO NOT play well together so I had to move to electric.

Yeah I could see that being the trade off. Especially because big electric fans pressed right up against the back of the radiator are now restrcting air flow through at cruise.

But its the exact opposite scenario I have with the 19" clutch. Mine will sit right at 178-180 while moving but if I pull into a drive through I will watch it slowly climb. When it gets really hot in the summer, I actually adjust the idle RPM on my Terminator from 800 ish to more like 1000 because the extra fan RPM helps some at idle.


Im working on a 66 Fairlane gasser project with a 429 based 503 inch engine. I am likely just going to hack up the core support in that car to make it fit a far larger radiator than even the 390 FE Fairlanes would have gotten. Im going to be super limited in fan space on that ride so I want all the cooling area I can get. But like you said, the downside is time sunk into fabrication. And I tend to be more of a function over form guy. So Ill get it in there and working, but its highly unlikely Im going to expend the effort to make it look pretty.

I was daydreaming last night about clearing out some of the stuff on my core support and behind it (coolant overflow bottle, battery, some electrical stuff) to stuff in a bigger (wider) radiator. The battery would be the biggest challenge unless I went trunk mounted. And I'm not ready for that.

I'm wondering if I could find a way to squeeze in a 28x17 core radiator. It would open up a whole new world of dual fan options, too. That would be an almost 20% increase in surface area. And that would bring radiator size in line with 2nd gens and other 70+ up platforms that realized the radiators were too small. Even the Nova realized this by 1975, and went bigger.

Thinking out loud.

Pulling my tsat gave me max coolant flow. My aftermarket ac has a heater hose throttle valve, so the timing cover recirc path and the radiator are the only two coolant flow paths in my setup. So I am thinking the coolant flow is maxed, no room to tweak this outside of exotic pumps.

The only two variables I can work with are airflow, and cooling area of the radiator. Insane airflow can crutch a poor surface area radiator, or a really big radiator could crutch lackluster airflow. Or crazy amounts of coolant flow could crutch a constraint on the other two.

Does the Chevy world fight the same battles on the first gen platform?

Thanks all, for the discussion. It makes me think back to my earlier adult life, doing arrow analysis with heat transfer equations for a reactor powered steam plant.;)

At one point, I was considering daisy-chaining a bunch of oil/tranny coolers on the heater hose side and hang them under the front end to increase the cooling capacity.
I never got around to that one. :bounce:

I did, however, build an inline tank to increase the coolant capacity by almost 2 gallons.

https://photos.smugmug.com/photos/i-...kpZ3QQF-X2.jpg
https://photos.smugmug.com/photos/i-...rg35CSf-X2.jpg

It helped a little, but I think the design was too blocky and caused too much back pressure. Throw in a 22-24 psi cap and I would regularly get zipper tears in the upper radiator hose when I made a hard run.

https://photos.smugmug.com/photos/i-...xcFpxTW-X2.jpg

I picked up an inline water pump a few years ago, but never did install it. I talked to the guys at Stewart and they swore by it, but then again, it's their job to sell them.
It seems like a good idea and I would think that it would help with cooling at idle. Especially in combination with an electric fan to help out.
Has anyone tried one of these?

https://photos.smugmug.com/photos/i-.../i-cN9CM8v.png

Those are all interesting. Did you feel that the extra capacity made a difference? I think you could probably use a 2 gallon fuel cell and be 90% of the way to being there rather than building one from scratch.

That inline pump is interesting too. My firebird needs just a small bit of help. I just needs a touch of help at a long idle. Ive been considering an electric setup, just because I already have a Terminator setup and I feel like Im wasting potential because I already have a build in fan controller.

I think that the extra capacity did make a bit of difference, but the design I used had too many hard turns in it and created too much back pressure. A fuel cell might work better if the flow isn't restricted. (In at the bottom, out at the top, with no divider plate.) The extra capacity has to help with spreading the thermal load, but I'm not sure that it will make enough difference to be worth the effort.
I think that if you put a fan on a large oil cooler or old heater core, plumbed it into the heater hose, and tucked it away in the fender or under the core support would be much more efficient at cooling than a little extra capacity.

I'm in the process of installing the Terminator X in my bird right now so I'll be switching over to it for PWM fan control.
I would strongly recommend the fan I'm using if you decide to go that way. You can see all of the details in my The Ultimate Cooling Thread
I can sit in traffic all day with the AC on and it will stay cool with this thing running!
I just realized that, since this fan is so much bigger than the radiator and I had to fab up a cover plate for the bottom of it, if I still have cooling issues at cruise this summer, I may mount a cooler or two at the bottom and try the heater hose idea.

Speargun, I just read your thread. Nice work. Interesting that you mentioned extra cooling capacity, a coworker and I were geeking out about this stuff last night, and he mentioned adding extra cooling volume. I didn't see how adding extra volume would help unless there was a corresponding heat sink that went with that volume, but I am glad you got some results out of it.

That fan in your thread is gnarly! I will keep that in mind. Good thread. I can't remember if I had seen it before, but I've only been back here on PY since 2024.

My nylon flex fan showed up today, the one that Sirrotica recommended. When you say the pitch of those blades is steep, you are NOT stretching the truth!:eek: The leading edge of each blade is flat, while the trailing edge flips up at about a 90* angle. I will install it this weekend and see how it performs against my baseline data from last week. I don't think I will see 67 degree night time temps for several months, but it should find itself in the 70's for a night cruise.

I am still going to look at the possibility of squeezing a radiator with a 28x17 core. Bigger radiator=more cooling surface area. This could also open the door for a bigger/better electric fan setup, maybe even a 28" wide Silverado dual fan from 2005+. Just 2.25 inches wider each side from what I have, based on seeing one of these: https://www.ebay.com/itm/256504481391

I might try the cooler in the heater hose thing on my channel. Fun and relatively inexpensive.

Only downside is I hate opening the cooling system. Messy and I swear I can feel antifreeze on my skin for days after I touch it.

Data...

I bolted on the nylon fan with a 1" spacer. It wasn't as deep in the shroud as desired, but the previous clutch fan setup was in a little deeper than half.

Took it for a drive, with outdoor temps in the 70's. It took a long time to heat up to 160. Stopping at a drive thru for several minutes at idle resulted in temps around 197. Getting back on the road to cruise speed brought things back down to 171, which was my previous cruise temp.

I got home, parked, and left the car idling for a good 10-15 minutes. Temp got up to 227. I didn't like that.

End result is that I saw roughly no improvement. I'm happy with 170-something while at cruise, but not being able to idle for an extended time is frustrating. And these aren't even the 115 degree summer months yet.

I have a few other fan combos I could try if I feel sassy. But I will be looking at other models and solutions, tho.

Just finished a 20 mile drive. Outside temps 67 degrees. Cruise at 45-50 mph and 2500 rpm yielded 158-160 degree temps. Even a 4 mile zip down the interstate at 65-70 and 3600 rpm barely cracked the low 160's.

Comparing this with last week's drive in virtually identical conditions, with only change being new fan, it dropped 10 degrees. I'll take that.

I still don't trust the car at extended idle, but I am pleased that in the current configuration I have a little bit of extra cooling capacity.

Was this with the same nylon fan and 1” spacer as yesterday?

how deep outside of the shroud?

Quick question
 

What size crank pulley & waterpump pulley.
Mine responded well to AC pulley setup that
Overdrives waterpump and fan.

Gerry

Yes. Maybe the 10 degree drop in ambient caused the 10 degree drop in operating temp, IDK. I didn't think it would be, but the numbers were the numbers.

Maybe 1/4 of the fan is in the shroud.

I have a standard 67 ac crank pulley setup, with what I think is the smallest diameter wp pulley. I can't remember the part number. Yup, we are on the same page.:)

This thing definitely needs air speed.

Another handful of miles, steady state cruise temp was 160, with ambient of 75. Even after shutting it off and it heat soaked, on startup it was 165 and came down to 158 after a half mile at 45mph.

Current setup is 11 bolt pump, small wp pulley, nylon "Sirrotica special" fan, Champion 4 core 23x17, no thermostat, close to a 50/50 mix of antifreeze, lower radiator hose of possible 1990's vintage, and no lower hose spring yet. Running FiTech and HEI, manifold vacuum advance.

Will post if I make changes. Curious to see how the AZ summer changes this, and how the ac affects it when I recharge it.

airflow
 

cant argue with results and yup mine runs right at 170 when moving too.
extended idle during a run she will creep toward 180 but drops instantly
moving. using a NOS 170 delco stat that due to paranoia I checked along
with a few others and this one cracks open 167ish and is fully open just over 180.
as long as my wife's meat thermometer is accurate. SHHH don't tell her i used it..
had to have a stat as would not get over 130 when temp was cool in morning or fall.

When I had factory NON AC pulley(.90 underdrive) and 5 blade powerflex fan i tried
every thermostat known to man. Even just a restrictor, and found at any speed all
was great but idle was enemy. Freind has a 78 TA with AC and had much less of and issue,
Duplicated the factory AC overdrive and then tried SD, HD and a STD fan clutch.
Never ever hear fan when moving or at idle. Only time i can hear fan is after i stop somewhere for a few minutes and car heat soaks up to 190 or so. Once restarted
fan engages briefly and temp drops fast back to 170.
Also the cold case radiator does cool better then when I ran the champion 2 row unit.
it holds more fluid and tubes are larger.

Seriously could your AC condenser be restriction to airflow at idle.

Also timing is a thought as too much or too little can be an issue.
keep at it!!

Gerry

A thermostat serves another purpose beside controlling flow through the system to stabilize temperature. It provides a restriction to raise the system pressure in the block and heads.

There are areas in the block and heads that are somewhat stagnant like dead end hallways that don't get as much flow due to the design of water jackets, most times towards the upper parts of the block and heads.

Steam can form in these dead end portions, if water pressure isn't sufficient the area that is hot has a steam pocket in it that will grow without enough pressure to keep the coolant in touch with the metal. Pontiac engineers addressed this in certain 421 blocks by adding an extra hole in the block deck to alleviate steam in those pockets. Most Pontiac engines do not have this hole drilled. It's cut out in the head gaskets, but in 99% of the blocks was never machined. Proof though that the engineers knew that there were areas that could be helped by more coolant circulation.

Thinking about your situation I would at the very least try a gutted thermostat, or an aftermarket restrictor washer. I would think a thermostat would also make your aftermarket FI system work more efficiently. I know from working on the later model GM stuff how a malfunctioning thermostat will mess the system up due to the water temp driving the system richer. Plus if your system adjusts timing by the ECM it will also have an effect on that.

I've actually never worked with an aftermarket system, but I would guess that it monitors coolant temp as part of the parameters to decide fuel air mixture as well as timing if that's part of your system.

At idle your water pump is by passing a portion of the flow through the intake crossover, but due to the lowered pressure at reduced RPM I would guess the block and head coolant pressures have also dropped due to no thermostat. This exposes those steam pockets to grow, and steam does nothing to cool an engine, as they grow efficiency nosedives. This could explain temperature creep at idle not just air speed through the radiator, but coolant pressure in the block and heads.

Anyway it's not a huge job to install a thermostat, or a restrictor to see if raising the pressure helps your condition.

With the nylon RV fan you can't get much more air speed at idle without going electric. My own opinion is I would never use an electric fan on an older Pontiac muscle car, most won't come close to an engine driven fan, especially the aggressive pitch one you currently have.

The other possibility is the Champion radiator isn't efficient enough, or it's scaled internally insulating it's ability to reject heat quickly. I used one of the nylon fans on my 73 T/A with a 455 and an A/C car on the street without any O/H problems. Granted it wasn't in AZ but it never even hinted at getting hot. Of course apples to oranges when you're comparing radiator surface area from a first gen F body to a second gen F body. I've owned both so I'm aware of the differences.

You might also try a heat sensing gun to check heat of different components in the system to see where you're losing efficiency. Likely no silver bullet and possibly a combination of small things instead of one single change will fix everything.

I can tell you that my parents lived in Phoenix since 1980, and their 75 Catalina with a 400 2bbl and air, with all stock components was fine for many years, until they traded off for a 89 GP.

Anyway, my next move if I was diagnosing the problem would be a thermostat, or restrictor to raise coolant pressure in the block and heads. You're not helping your problem with no thermostat. Most people will tell you it can help a cooling problem by slowing down how long the water is in the radiator, when in fact pressurizing the block is what actually brought down their coolant temperatures. Electrons move heat, so slowing the water down so it can reject more heat is a wives tale, pressure change though is a real change that can have an effect. Covering more surface in the water jackets with coolant will have a real effect.

Keep plugging away, you'll get it figured out.

Sirrotica, I appreciate the input.

I suspect the back of the block gets the least cooling and would be more prone to localized boiling. What might make it worse is my ac system's heater control valve, which stops all flow through the core, and prohibits the 3rd parallel flow path in the cooling system (heater+recirc+radiator) Without the heater flowpath the coolant won't have as much differential pressure to promote flow at the backside of the passenger side of the block, which equals bad. But then again, if there is no bypass flow through a heater hose, then it would provide more flow capability through the radiator path. Which benefits more? I don't know.

More flow is always better, even in those localized hotter spots. As nucleate boiling occurs along the channel walls, more flow strips away the emerging steam bubbles, which is great heat transfer. Lower flow allows the steam bubbles to coalesce, which creates a steam layer that drastically inhibits heat transfer. Yeah, that back half would have the lowest flow. Maybe that is why Pontiac (maybe all GM?) got rid of heater control valves early in the 70's?

Steve Barcak years ago talked about the hole in the deck surface that needs to be drilled, so you reminded me that was a thing.

I'd be curious what kind of dead head pressure a Pontiac water pump could make, and how much that pressure head takes things away from saturation. There are two means by which to keep from boiling: increase pressure, or lower temperature. If you increase back pressure, you move the system farther from saturation. But you also reduce flow, which reduces heat transfer, and promotes more saturation conditions. Which one wins the day?:nerd::D

With regard to the Champion, I remember Chris Casperson years ago proving to me that a properly designed 2 core is better than a 4 core - number of rows isn't the only metric. Total surface area of the rows is what matters.

I'm gonna roll with my Champion for now, unless I can find a way to squeeze a 28x17 radiator in. Battery tray placement is my current limiter for that. I STILL have yet to do a good chemical flush of the system to possibly address any surface area sludge coating. And I still need to replace lower hose and spring.

Yeah, the idle heating bothers me. It is very manageable for now, but it seems like it will be very air speed and ambient temperature dependent. And then there is the AC charge coming soon...

Yes, the EFI fattens up the fuel mix when less than certain breakpoints. 170 is the default FiTech breakpoint for normal op temperature, but I recently found out that I can change that. I set it to 150 for my current configuration.

AC got recharged, now I have interior frosties. Took it for a drive, and saw a 5-10 degree increase with ac on max. Still stayed under 170 except when stopped at a stoplight/idle. Then it would come back down slowly once cruising again.

One thing I will also address: My trans cooler might be inhibiting some air flow. It sits in front of the condenser, and might be staying up the air obstructions. Gonna move it out of the way, down lower toward the chin valence/parking light area. Every little thing helps.

"Staying up the air obstructions"? Grrr!

Stacking. Stacking. Stacking.

Staying cool
 

Pic was taken on return from 45 minute run this morning.
Very hot & humid today. Driving at 30 mph
with rpm’s at 1200ish. Just loping along.

Gerry

Nice!

Me? Still trying to find the answer. Ambient here is 100+. Drove a handful of miles with the ac on yesterday, and stoplights shoot it over 200 quickly, and it takes forever to slowly come back down. It comes back down to mid 190's eventually if I can avoid stoplights.

Now is a time of the year I don't want to work on it to fix any issues.

My tentative plans, in no particular order:
Relocate trans cooler to make sure it is not blocking air flow
Explore fan options, including a high flow electric option.
Look at different radiator options, including wider, with more efficient tube options other than my 4 core aluminum.

If I didn't have so much other expensive stuff to buy for my Gasser project I would really like to try one of those inline EMP water pumps posted earlier in this thread.

The firebird just needs a little help when at a dead idle. I was driving it in this midwest heatwave over the weekend. Moving even at relatively low speed, dead on the thermostat. But if you get caught at a stop it start creeping. Takes a good long while to get into danger territory. But its enough that the thought of getting caught in a bad traffic jam scares me.