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If you mounted your AC condenser up front to get better cooling, what makes you think putting a radiator in back will do any good? You could just take the load of the radiator and mount the AC condenser at the back where the factory put it!

Does it run hot just in traffic, all the time? What water pump, thermostat, fans? Many people chase a perceived problem when the gauge reads off, does it boil over?

Here we go again, trying to do long distance analysis of a cooling problem. without knowing there really IS a cooling problem.

this statement of yours, “can’t quite run it in the Phoenix summers” provides absolutely zero information on what you perceive to be a cooling problem.

WHAT is your cooling problem?

High temperature gauge reading at highway speeds, high temperature gauge reading idling in the driveway, bubbling and gurgling indicative of boiling water in the heads of the engine and if so when and after what driving experience, discharge of boiling steaming water from the overflow tank when the car is parked and turned off??

do you have cooling problems in the summer without the air conditioning being on?

have you used an infrared heat gun to check temperatures of your cooling system components?

Is the 428 a new motor that has always had cooling problems since it was installed?

how old is your thermostat? are you using a thermostat?

are you sure you have removed all of the air from the cooling system?

please share with us the symptoms that cause you not to drive your car in the Phoenix summer.

please share with us what troubleshooting steps you have already taken and what those steps revealed.


Correct.   New Titus Cleveland engine, 4in stroke, 120 over, 427.6 , mild street motor, runs great.  Haven't been out much because it's been mostly 105-115 the last couple of months.  No issues on the freeway where there's plenty of airflow and it sits at 204.  Still testing around the area where I can average 20-40mph.

Mostly curious if anyone had tried a 2nd aux radiator for additional cooling.  Strange as it sounds I'd like to actually be able to drive it in traffic in Phoenix in the summer time without having to worry about being caught in slow traffic.

And yes I know how to bleed the cooling system.   The last time I drove it in 110 degree traffic it blew a fan fuse and hit 230 by the time I got home.   Bubble/gurgling on shutdown... Hasn't done again that in the last couple of test drives.  I have Jon's nice fuse box so it's easy to see/replace.  Just can't see it while driving.

No, I've not tried driving with the ac off... That's miserable!  I probably will test that though.  I'm still in the testing/review phase with only 100-150 miles on the new motor.

From your description ti sounds like the overheating was predicated by a blow fan fuse, so rather than an overheating issue you have a fan issue / root cause and we need to address why your fan is drawing so much current to blow a fuse.

I assume you have sucker fans with the AC condenser up front? What type, shrouded or not? How far do they sit from the radiator? As silly as it sounds many a fan has been wired backwards!

I was surprised when it gurgled at 230 with a 20psi cap on the swirl tank.  I'd have thought the boiling point would have been a bit higher.  No I didn't install the 20psi cap. My Pantera mechanic "upgraded" my 16psi cap...

The Ron Davis radiator comes with two fully shrouded 13 inch Spal sucker fans wired correctly and blowing in the right direction. It's a common radiator used by many Pantera owners.

I may need to confirm there's nothing else on that 25amp fuse.

Tell us about your water temperature gauge. OEM sender installed in the engine block to an OEM gauge, or?????

do you own an infrared heat gun?

do you know if your fans are wired off of one fuse or two fuses?? Should be two  

if everything is operating correctly you should be able to park in the shade on a 100° plus day and let it idle for 15 minutes without overheating.

For reference I have a newly installed 404 stroked Cleveland with a Ron Davis radiator sourced from Dennis Quella. I suspect it is likely what you have installed in your car.

Steps taken with my cooling system:

OEM coolant design with SS tubing, aluminum heads, Edelbrock water pump, overdrive water pump pulley, 180° Tim Meyer thermostat with OEM brass restrictor plate  and 16 psi radiator cap.

last week I parked outdoors in the shade with ambient air temperature of 103°  I let the car idle for 15 minutes. It never got above 200°

204° during highway cruising is not an alarming temperature at all, but I do think it is higher than what many owners experience.

please go back and read my earlier post and provide answers to the questions I posed. Without you providing those answers you will not be able to receive well-informed responses.


Last edited by lf-tp2511


The problem you're having should not exist, if everything in your cooling system is working properly. I have a similar motor to yours (427 cubic inch, Fontana aluminum block, SVO aluminum heads, etc.). A week ago, I was driving around in Placerville/Shingle Springs, CA in 100+ degree temps and my coolant temps were exactly the same as they always are. I even got caught in road construction, where I was stopped and idling for about 20 minutes. My temps didn't rise by a single degree from my normal operating temperature. I have 2 temp senders and gauges, so I know the readings are accurate. My max temp is 186 on my Holley EFI gauge and 190 on my OEM gauge. I also use an 8 psi rad cap without an issue.

First things first: are you sure you have the correct 351 Cleveland thermostat and bypass plate just below it? You have a Ron Davis radiator with dual 13" fans mounted in a shroud. Do both fans turn on at the same time or does one turn on before the other? If it's the latter, do you have a baffle between the fans that isolates the fans from one another? If you don't, you need one or you need to make it so both fans turn on at the same time. If there's no baffle and only one fan is "on", it simply sucks air through the opposite fan opening, not through the rad. PWM control of both fans is the best way to go. Pantera Electronics' fan controller works this way. PWM varies the fan's speed according to coolant temp.

If you're still looking to improve your cooling, George's self bleeding mods work great. Just because you get all of the air out of the system doesn't mean more air bubbles can't form through tiny system leaks, hot spots or pump cavitation. These mods are constantly bleeding air out of the system. I even have bleed fittings in the rear of my cylinder heads.

There are other things you can do to improve the efficiency of your cooling system but they require fabrication work and re-plumbing of the system. When it comes to cooling, fluid velocity is everything. Your mechanical water pump was never designed to pull coolant through 20 feet of plumbing! I have an electric booster pump at the outlet of the radiator. It makes the mechanical water pump's job easier, helps prevent cavitation and the air bubbles that result. It can also circulate coolant after you shut the engine off, to help eliminate hot spots. It really helps at idle too, as it flows more coolant than the mechanical water pump does (at idle).

Aftermarket rads, designed for Pantera's, seem to always be dual pass rads. I assume that's because it makes it easier to connect to the OEM plumbing. A single pass rad is a bit more efficient as it reduces restriction to flow. The more time that coolant spends in your rad, the less efficiently the rad works. Tip: Ron Davis will sell you a single pass version of their dual pass rad. You can even fit two 14" fans but you'd have to have a custom shroud made.

Another interesting mod is John Taphorn's remote, by-pass thermostat mod. This mod removes the thermostat from the motor and puts it at the inlet to the radiator. A bypass line is added to the system so coolant by-passes the rad until the thermostat opens. The benefit of this is increased velocity of coolant through the system, particularly during warm-up. John used a BMW remote thermostat but IPSCO now has remote by-pass thermostat housings. The GT40 crowd seem to have embraced this mod.

Finally, aluminum block based engines can benefit from an oil/water heat exchanger. Aluminum blocks grow quite a bit from cool to hot. They are usually built with tight clearances cold, so clearances are normal when the block is at normal operating temp. An oil/water heat exchanger cools the oil when it's hot but also serves to heat the oil when it's cool, as coolant warms up much more quickly than oil does, particularly with a 10 quart oil pan. This helps to get the block up to normal operating temperature more quickly.

Last edited by davidnunn

Agree with David WRT the mods, especially the self-bleeding GP swirl/overflow tank modification - actually I believe this configuration was how the GT-40s were configured, and was a Carroll Smith setup.

Anyway, I run this config on my cast iron blocked / headed engine (dyno’ed at 425 HP).

My engine builder added head bleeds running from the rear of the heads to the overflow tank (which is under suction).

These mods gives automatic air removal from the radiator, swirl tank, and both heads.

It seems to work well for me, with no spewing coolant, and no boiling sounds in Tucson.

I run a Hall Phoenix radiator (brass), Meriah fans with no shroud (other than the one connecting all the blades), a 185* RobertShaw t-stat with the brass plate installed, and a Stewart Stage I water pump (from Summit) - it has a cast iron body.

The cooling system mod is best implemented with the engine out of the car - which I’m sure you’re hoping not to do.

Good luck with this…  


Last edited by rocky


If your radiator has a standard top air bleed line back to the overflow tank via the fixed under car bleed tube , check the undercar bleed tube is not blocked and actually is venting properly  .

I just replaced the entire under car bleed system as the steel bleed tube was blocked virtually the entire length with a solid sludge buildup. I replaced it with a 6mm 316 SS seamless tube. I cut it up when it was out and except for the very ends it was  blocked all the way. 

It easy to think something is working just because its there....and if this bleed line is blocked  it can be quite difficult to ensure all of the air is actually  out of the top of the radiator and overall system.

Once the coolant in the RHS radiator tank has an air bubble in it , because of the location of the fan thermostat bulb at the top of the RHS tank , the presence of air can affect the thermostatic fans from cycling correctly , as the temperature bulb in the radiator is contacting low conductivity entrapped air not  coolant fluid. This rapidly results in a cycle of overheating events as the fans don't activate. More boiling , bigger coolant loss , larger air bubble , and around it goes.

Hence symptoms like you are describing.

Low speed cooling problems in a Pantera are usually an air flow problem. Are you sure that both of your cooling fans are getting up to full speed? As someone else has already mentioned that an oil cooler can help to keep water temperatures down. I also have a front mounted air conditioning condenser and used the space where the condenser was to install an oil cooler. Since you have an aftermarket aluminum block as I also have, you should not have the Cleveland engine thin cylinder wall hot spot problems.

As often happens, the original poster of this thread is less active on the thread than those of us trying to help him.

all of the advice that has been given in recent postings is of NO value until we…..


From what little Rick has shared with us, it appears he has a stock cooling system except for an upgraded radiator and fans.

this is a configuration that is more than capable of correct cooling performance, if the rest of the system is also correct.

but we don’t know if it is correct because we don’t have the necessary information from Rick.

how about we stop confusing Rick with an endless list of upgrades, until we actually determine all of his system is correct.

And we can’t make that determination with the little information he has provided

I am out of this thread until Rick provides better information and feedback

My 2¢……


Yes I'm a bit swamped with work and can't mess with the car as much as I'd like.

Today's test and the answer is.. hmmm.

The neighborhood loop is 3.8 miles where I try to average under 45mph / 2500rpm in 3rd gear.  Ambient temperature started at 95 and finished at 98.   IR before starting shows everything on the car at 92-95.  After 4 laps the average temp stabilizes at 206.  For less than a half of a mile I ran in 2nd gear with it 3000-3500 rpm and it climbed to 212.  Back in 3rd/2500rmp and 3 laps later it's toggling between 208-210.  Then for my last lap and a half I turned the ac on and it climbed to 219 before I turn off and headed home.  In the garage idling it climbed to 228 where I shut it down.  No gurgling/bubbling though.  The factory 260 gauge was pointing to the first tick after the 190.  IR didn't show the back of the head or the radiator over 200-205.  Not sure how effective it is against shiny aluminum. 
RonDavis radiator, fans both working.  No automatic blead from the radiator to the back.  Likely removed by the prior owner 20 years ago.  Water pipes all in the stock location more or less except they're 1 1/2 verses 1 3/8 except where the hit the swirl tank where my mechanic radiused them from 1 1/2 to 1 3/8.  Have the higher flow aluminum upper water pully.  No heater hoses.  One port is plugged and the other is used as the Fitech water temp sending port **.  The Fitech handheld gives water temp readings from that port in 1 degree increments.  At 190 both the stock gage and the Fitech are in sync.   The factory gauge temp sender is in the recommended location.  I'm using a stock Stant 180 as the Titus block does not have the Cleveland bypass setup.

Is the temp from the stock temp sender reading water return from the radiator?
My "assumption" is that the Fitech sender is reading the temp heading out towards the radiator?  If so what would the max acceptable out bound temp?

Thank you for giving us more information about your system and how it behaves.

The warm radiator confirms you are circulating water. You are over spinning  the water pump, which is good. You have a 180° thermostat which I personally believe is the correct value. You say the temp sender is located in the “recommended location”, which I trust is on the front of the engine block.

honestly, all I see are some high temperatures. those are just numbers, and absent any actual performance/durability problems, the numbers just serve to cause concern.

you noted your temperatures rose after you let it idle in your garage, which is probably not a good thing.

despite you having a  good radiator and good fans, it appears there is not enough air moving through the radiator at low speeds.

I would think that you would have a aluminum “box” shroud for both of the sucker fans. If you only have sucker fans mounted, then a large part of your radiator is not seeing air movement unless driving at speed. If that is the case that needs to be addressed.

I would like to know what temperatures you see after idling in your driveway for 15 minutes.

most sources indicate an operating temperature of 220° is not out of normal.

honestly, all I see are temperatures that might “appear” to be too high.

let me share a little bit of pantera service history. In the 1970s most cars just had temperature idiot lights, not an actual gauge. Many  Pantera owners’ first experience with a temperature gauge was their  pantera, and when they saw the needle swinging “too far” to the right they thought something was wrong. So many cars were coming in for cooling system service that Ford actually came out with a technical service bulletin to correct the problem. After the TSB was performed, the gauge needle did not travel as far and the owners were satisfied that the TSB had solved the problem. What was the TSB fix? The technician soldered a resistor into the gauge sender circuit, changing the resistance and thus changing the action of the gauge. Moral of the story? A number is not necessarily indicative of a cooling problem  


Last edited by lf-tp2511

Rick, how are your fans wired? You might want to try temporarily connecting them directly to the battery, to see if their speed increases over how they’re connected now. A fan blowing a 25 amp fuse might be a sign of a bad connection or bad ground; either of which will cause your fan(s) to turn more slowly than they’re designed to.

If I were you, I’d call your block manufacturer and ask them what they consider to be the acceptable range of normal operating temps. Aluminum blocks grow a lot from cold to hot. If you’re running too hot, your bearing clearances may be getting too big, too. How’s your oil pressure at 220°F? For this reason, it’s very important for you to control the normal operating temp of your motor. You shouldn’t need a 20lb rad. cap to keep from boiling over, even in AZ.

Ok. Yesterdays IR reading are junk.  The IR gun needed a new battery and you can't get accurate readings off of shiny aluminum!  Started today test run with ambient temp of 99, concrete driveway at 136, asphalt road at 156, everything on the car at 97-98, with the ac on at the lowest (least cooling) setting.  After 4 laps it slowly increased to 212 and I pulled  into the garage and took the 215 pic.  The numbers from the back of the heads showed under 200 until I put tape on them and then both were 235-245.  Can't hear any gurgling until after shutdown and then there was just a little bit.



Fans were wired through relays 5-6 years ago after a console switch got fried.  I'm not technical enough to comment on the quality of it except to say that the people helping me were engineers that work with electrical issues professionally.

Yeah, I'm going to switch the cap back to the 16psi cap I had there originally.  I didn't ask for the 20psi cap.

Only 1 fan fuse blew and it's been fine since.  I am considering getting the wiring reviewed by my mechanic to see if a larger gauge pulling directly from the source would make any difference.

Oil pressure was on the tick halfway between 35 and 70.IMG_0151

Yes it's a fully shrouded radiator.  To my untrained hand test the drivers side (the one the the fuse blew on) seems to blow a little more air than the one on the passenger side. All the hoses are gates green stripe and that piece is the longest one. The rest are much shorter.  I had a issue with a too long piece that was not gates green stipe a few years ago!  Lesson learned there.


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