[Squidward]

Originally Posted by 68 Firebird

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

Gerry

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.

[Squidward]

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.

[68 Firebird]

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

[Sirrotica]

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.

[Squidward]

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?

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.

[Squidward]

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.

[Squidward]

Originally Posted by Squidward

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.

[68 Firebird]

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

[Squidward]

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.

[RocktimusPryme]

Originally Posted by Squidward

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.

[Sirrotica]

Squidward, During your investigating into different radiators, you might be interested in a double pass radiator that makes the coolant travel from left to right, then again back to the left. his could get you over the hump as far as longer exposure to the coolant into the airstream.

Link explaining single, double, and triple pass radiators:

https://www.speedwaymotors.com/the-t...fference/28862

[RocktimusPryme]

Originally Posted by Sirrotica

Squidward, During your investigating into different radiators, you might be interested in a double pass radiator that makes the coolant travel from left to right, then again back to the left. his could get you over the hump as far as longer exposure to the coolant into the airstream.

Link explaining single, double, and triple pass radiators:

https://www.speedwaymotors.com/the-t...fference/28862

I remember reading that article a while ago.

What I don't understand is with cooling being a widespread issue with classic cars, if double and triple pass radiators were more effective than normal radiators, why haven't they been more widely adopted? I mean it seems like a simple adaptation if they worked significantly better. A minor irritation to re-route one cooling hose for a double pass, but not a mountain of a problem.

[Sirrotica]

Those radiators aren't made for every application, they need to be adapted so most people run them only on fabricated race cars.

In the oval track world you will see them quite often and they are more efficient to the tune of 10-20% over a single pass radiator.

Before these radiators were available I used 2-3 core radiators mounted back to back in my race cars. First pass through the front radiator, second pass through the rear radiator.

It didn't matter how hot the ambient temp was you couldn't get the coolant above 180 even after a 20 lap feature race. That along with the composite fan ended my cooling problems, for 3 years after the car never overheated.

More air, more surface area, and more coolant capacity means the heat rejection ability will increase.

[JLMounce]

First gen's have undersized radiators and that's 3/4's of the battle. Everything has to be inline for them to cool effectively in all situations.

Like you, my 69 bird cools fairly decently while moving, but will creep at lights. in 100 degree heat, it cruises around at around 188 with a 180 degree thermostat. Sitting at a light, it will slowly creep. It takes about 5-8 minutes to reach 205, which seems to be a long duration light in my area. It takes about 15 minutes to reach 210.

My setup is a cold case radiator with a Flex-a-Lite black magic 180 fan. I also have the upper and lower closeouts on the car.

The problem with this setup is that the black magic fan, while claimed to be 3300 CFM and in a conical shroud seems to be a beast, it doesn't completely seal against the core. As a universal part, it hangs over the top and the bottom of the core by about 1/4". Additionally, the cold case radiator does not sit flush with the core support like the factor radiators did. There's about an inch to inch and a half between the core support and the radiator core.

As a result, I believe that while sitting still, the fan's suction across the core is reduced because it's pulling air around the gaps to the core. Then, what air it is pulling through the core, is recirculated hot underhood air as opposed to ambient air.

heat transfer across the cores is more efficient as the delta between the coolant and ambient air increases. If you're driving along and the radiator is seeing 100 degree ambient temperature and 180 degree coolant, you have an 80 degree delta. If you're stopped at a light or in traffic and the radiator is seeing a mix of underhood temp and ambient at lets say 140 degrees, you have much less efficiency. You would further degrade this efficiency as the air passes through the first core, into the second core. Heat transfer has already occurred, the air has taken on that additional temperature and the 2nd core has less to work with.

This is why you see thin modern radiators. Frontal area of the radiator trumps number of cores every day of the week. Fans area also much more efficient at drawing air through a thin radiator.

My next steps are designing a shroud for this radiator that fits the entire core, without gaps. I will attempt to use the dual 12" ProForm brushless fans that I hear really good things about, with a claimed 4200 combined cfm and provide as much flow through channels on the shroud as possible for highway driving. I will then close off the front side of the radiator to the underhood air as much as possible. I think that's going to be the ticket.

A quick FWIW on my setup. I have an engine that makes 580/600 and the vehicle is also driven between 4500-5500 ft. Because of the density of air here, it is more difficult to cool an engine by nature. At sea level my combination may be fine as is and would likely cool a stock or near stock car adequately as well.

[fyrffytr1]

I am not very smart when it comes to everything you all are talking about, so I will just share my experience with running hot. I live in southwest, Georgia and the temps can reach 100 degrees during the warm months(February through December!). My car is a 67 GTO with factory air. I could not drive it when temps topped 90. Long story short, I scratched the paint and thought I was going to get it repainted, so I took some of the trim off the car. The hood insulation pad was worn and I decided to remove it until I could replace it. I drove the car after that and the temperatures dropped a lot. I only have the factory gauge. Before it would hit the 3/4 mark, but after removing the pad it doesn't even get to the halfway point with the A/C on sitting at idle.

[nUcLeArEnVoY]

Another thing here is our interpretation of what's hot and what's not...

Has anybody actually seen these temps keep rising into critical territory (i.e. 230+) when idling, at which point it's acceptable to deem it as a problem? 220 is up there but it's still in the range of normal operating temperature. Hell, it's smack dab in the middle of my particular car's temp gauge. It's summer and we are talking about dense, humid air in 90+ degree ambient temp. I think if our temps are creeping to 200, 210 but slow down or stop there, we are doing okay, all things considered. I know it's not ideal for carbed engines, plus with the volatility of modern fuels, but sometimes there's no amount of cooling capacity you can toss in that will trump thermodynamics.

I have a feeling most of these cars ran warmer when new than we allow them to run now. Not because they were not taken care of, but when new, they were just regular everyday cars that most owners didn't coddle or glue their eyes on the temp gauge 24/7 while driving. They probably weren't even paying attention. Modern cars, assuming they're even equipped with a temp gauge, are HEAVILY dampened now as to not frighten owners by showing the normal fluctuations in temp as they drive - they just stay around the middle of the gauge no matter what unless they are legitimately overheating. The service manual will even specify that hot running and overheating can occur during extended idling, so by virtue of how these car's cooling systems were designed may make it difficult to prevent them from getting toasty during extended idling. The thing is, 200-220 is not overheating, lol. It's not even running "hot." Hot is once you get over 220. Idiot lights for such-equipped cars don't even turn on till' 260.

Don't get me wrong, I love seeing the needle on my car rarely ever even pass the first "160 degree" peg (which is what I've always interpreted it as), and I'm not trying to advocate to just say screw it, let them go and potentially overheat, either. Just maybe, since it's summer and hot af out... cut these cars, and ourselves, some slack. If the temp creep slows down or stops at 210 or 215 or whatever, I'd say that's okay.

I dunno, don't mind me. Lol

[JLMounce]

Originally Posted by nUcLeArEnVoY

Another thing here is our interpretation of what's hot and what's not...

Has anybody actually seen these temps keep rising into critical territory (i.e. 230+) when idling, at which point it's acceptable to deem it as a problem? 220 is up there but it's still in the range of normal operating temperature. Hell, it's smack dab in the middle of my particular car's temp gauge. It's summer and we are talking about dense, humid air in 90+ degree ambient temp. I think if our temps are creeping to 200, 210 but slow down or stop there, we are doing okay, all things considered. I know it's not ideal for carbed engines, plus with the volatility of modern fuels, but sometimes there's no amount of cooling capacity you can toss in that will trump thermodynamics.

I have a feeling most of these cars ran warmer when new than we allow them to run now. Not because they were not taken care of, but when new, they were just regular everyday cars that most owners didn't coddle or glue their eyes on the temp gauge 24/7 while driving. They probably weren't even paying attention. Modern cars, assuming they're even equipped with a temp gauge, are HEAVILY dampened now as to not frighten owners by showing the normal fluctuations in temp as they drive - they just stay around the middle of the gauge no matter what unless they are legitimately overheating. The service manual will even specify that hot running and overheating can occur during extended idling, so by virtue of how these car's cooling systems were designed may make it difficult to prevent them from getting toasty during extended idling. The thing is, 200-220 is not overheating, lol. It's not even running "hot." Hot is once you get over 220. Idiot lights for such-equipped cars don't even turn on till' 260.

Don't get me wrong, I love seeing the needle on my car rarely ever even pass the first "160 degree" peg (which is what I've always interpreted it as), and I'm not trying to advocate to just say screw it, let them go and potentially overheat, either. Just maybe, since it's summer and hot af out... cut these cars, and ourselves, some slack. If the temp creep slows down or stops at 210 or 215 or whatever, I'd say that's okay.

I dunno, don't mind me. Lol

All accurate. If I'm not mistaken the idiot light on a 1969 Firebird was not set to illuminate until 240 degrees and that gave you 10-20 degrees buffer before actual boil-over starts to occur.

The hottest I have ever seen my car was a bit over 230 degrees and that occurred in 95-100 degree weather in a long line getting into a car show. I don't really recall how long we sat in the line, but it was long enough that most everyone was cycling their engines on/off not only from heat, but also simply because of the amount of time. I want to say it was between half hour to 45 minutes.

That was when I was still using the factory shroud and a 17" metal flex fan without a clutch.

[RocktimusPryme]

I also generally agree, however I will say that when I was having the most trouble last year My 67 when the car is over 200* and the ambient air temps are 90+ degrees, it did start to audibly ping. So while mine has never got to 230, it also hasn't ever got to a point in where I was positive it would stop. Ive always chickened out.

Turned out I had a worn out T-stat housing that was letting the thermostat sit crooked and not seal. That was causing the car to get hot even when driving, not just sitting.

But yes in general I think we care too much about keeping old cars at 160. My C6 regularly ran 210-220.


Side note with my 1st gen. Its very sensitive to being full. If its missing even what seems like a few ounzes of its capacity, that difference shows up in the gauge.

[srmmmm]

My problem is exactly the opposite, over cooled at idle and slow speeds and under cooled at highway speeds. No problem idling in traffic with the A/C on and ambient temps at 100 degrees. It barely hits the thermostat rating of 180 But try to run 70 mph with the A/C on and the engine temp will rise to 230+.
I'm replacing the original 4 row copper/brass radiator that had been repaired a couple of times, but really never rodded out. I suspect insufficient coolant flow from scale buildup and insufficient airflow from too much paint on the fins.
Hopefully the new aluminum radiator will cure the highway temp issue.

[JLMounce]

Cold Case does offer this.

https://www.coldcaseradiators.com/pr...it?sku=CHC11RS

It's a complete fan/rad/shroud solution for first gens. I believe that the sizing is comparable to the A-Body and 2nd Gen Firebird size. It's not cheap however and installation requires almost complete front end disassembly. I would try and buy this kit without the fans, as the supplied fans from CC don't have great feedback. I'd replace them with these bad boys for close to 6000 cfm of tug across the core. https://www.summitracing.com/parts/pro-67035

I'd also add reliefs in the shroud with flaps to allow as much airflow at speed as possible. This is admittedly, out of the budget for many people however and not practical unless the car is already apart.