Early Mustang Cooling Systems Part 1: How Thermostats Work & How to Select the Type & Temperature!

Early Mustang Cooling Systems Part 1: How Thermostats Work & How to Select the Type & Temperature!
In this video I introduce you to the way I manage cooling systems on vintage Mustangs and other cars and trucks from the era. I’ll break down the cooling system into the different areas that impact the system’s overall performance and start with the most misused part, the thermostat.
Part 1: This Video begins with an overview of cooling system operation, broken down to six areas, and turns to focusing on the function and correct application of the thermostat, with insight on how and why choosing the correct thermostat temperature rating is critical to cooling system operation.
Part 2: This video goes into detail on radiator selection and how to choose the design that is best for your needs. I’ll go in depth on the important design elements that will make or break your cooling system operation, and debunk the myth that bigger radiators are always better. The discussion will look at fluid capacity and the ability for the radiator core to perform as a heat exchanger.
This series of videos is something I’ve wanted to do for quite a while and now that I’m in the middle of rebuilding the cooling system for my 1966 Shelby GT350 Mustang, it’s the perfect opportunity for me to share my knowledge with you.
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#shelby #ford #mustang #gt350 #shelbygt350 #mustanggt350 #shelbymustang #v8 #cooling #coolingsystem #overheating #thermostat #temperature #coolant #electricfan

[@JuanCM1957]

Thank you, this is the best explanation I’ve ever heard about the operation of a thermostat.

[@jordanparker8359]

Excellent video answered my questions! Thank you!

[@user-sw8cm9zy1d]

Thank you so much for explaining the thermostat. You are spot on, i was having this problem. I changed to a 180,from160. An so good. Looking forward to the rest of your video's

[@dennisparass5531]

Superb…really helpful👍👍

[@livinlarge602able]

Great job! Completely sorted out all the misinformation out there. Really good explanation thank you for the clarity.

[@xavierdelpino3072]

Wow. Great video!

[@TheGT350Garage]

Thanks!

[@Joe.Kramer]

Very helpful, informative, and explained excellently. 10/10

[@leokelley839]

Hi Walter, Can't thank you enough for the cooling system education. After years of overheating issues, 6S1964 is running better and steady at 195-205d- thanks to the high flow 195d thermostat! So much more fun to drive w/o worrying about overheating. Happy motoring!

[@TheGT350Garage]

Excellent! Glad I could be of help. With the dual point, make sure your timing is in the 12-14° range at idle and the distributor curve comes into full advance between 2800-3000rpm. Any sooner can be a bit over advanced if you get into the throttle hard. These engines seem to be happiest at around 32° total, 34° is the absolute limit on modern gas. Make sure the advance mechanism gives you the correct 20° and no more, if it exceeds that, the limiter bushing is likely missing on the advance limiter arm beneath the points plate.

[@Chris-mp5zw]

Big help Thanks

[@jc-qc3yu]

Thank you excellent video 🤙

[@jc-qc3yu]

You are 100% right I can’t tell you how many people I talk to like you said in your video that work on cars for so many years and don’t know shit about cooling systems they barely know how it works is right that is 100% true … I’ve been working on cars for 25 +years and your video is 110% correct the ancient thinking of cooler is better is absolutely wrong and I remember in the video you were talking about the chips they used to sell in the 90s oh my God was that a joke lol thanks again buddy

[@TheGT350Garage]

You’re very welcome, and I appreciate the comments. Now that these cars rarely see the inside of a repair shop and the majority of work is done by home mechanics, this knowledge is being lost. It’s not just about making videos on KZbin for me, it’s about preserving my knowledge and the knowledge I’ve gained from others for the future of the hobby.

[@chiconian49]

Great presentation. I bought my first 65 Ford with a 289 in 1968. I live in California very hot Sacramento Valley. My little convertible began overheating. Fortunately I took an elective high school auto shop class my junior and senior years. My teacher used my car as an example of how to stop overheating in small block Fords. We replaced the 2 core stock radiator with a used, rebuilt 4 core radiator. As you know, Ford used the same cheap 2 core radiator with their inline six's and V8's. We also replaced the old factory thermostat with a 195 degree thermostat. We we instructed by our teacher to change the thermostat and coolant every two years. Problem solved.

[@TheGT350Garage]

The stock thermostat in 1965 was actually a 195°F model. Most of them were changed to 180°F or 160°F by the late ‘60s to early ‘70s. More coolant volume definitely helps as long as there is enough airflow to get the heat out of it. In the late ‘80- through the ‘90s and even now, companies sell radiators that have more tubes and fins than original equipment, but they sacrifice the flow of air and in some cases compound the cooling issues faster than they can cure them. Old school green ethylene glycol coolant does need to be changed every two years, but not because the coolant causes overheating, the additives that protect the cooling system deplete and need to be replenished.

[@chiconian49]

@@TheGT350Garage I bought the car used so who knows what thermostat was in it. I just remember my teacher telling me the old thermostat was the wrong one. I assumed it was from the factory.

[@jackieross3831]

Had to add more comment thank you for speaking clearly you were very easy to follow Easily to understand

[@dougboyer4002]

Thanks it was very much an informative session. It’s seems almost counter intuitive based off of the 195 thermostat. But you made it make sense I’m in the process of of rebuilding a 1970 mustang and I had ordered a 180 but I’ve reorder a 195.

[@TheGT350Garage]

Maximize airflow through the radiator and get the ignition timing dialed in and it will run consistently in all weather.

[@nathannelson7020]

I just made this mistake! I thought a lower temp thermostat would keep my 66 cooler 😔 thank you so much!

[@osteodoc7982]

Awesome video. It gives me a great deal more insight regarding the cooling system. I just purchased a '67 GT500 conv tribute (wish it was the real deal) from VOLO, and unfortunately, I didn't do my due diligence and fly out to test drive the vehicle. I based that on the 100% feedback and satisfied customers. The shop manager hasn't been helpful other than to say that, "it sounds like it needs a different radiator/fan setup". I even included photos of the whole system that includes what appears to be a March Performance Serpentine kit. It appears high dollar. After watching your video, I can't help but wonder if it's been set up with a 160 thermostat (or maybe it's just stuck in the open position). I was planning on a 180 but given it's a performance 351W, I think I'll follow what you're using with the 195. It makes sense. Thank you again for a great video.

[@TheGT350Garage]

So, the ‘67-70 radiator supports have a wider opening for a larger radiator than the ‘65-66 cars. But there was a narrow (Non-A/C) small block radiator and a wider (With-A/C) small block radiator that was closer in size to the big block radiator. With the narrow radiator there are two spacer plates that seal the radiator sides to the core, without them air passes by the radiator instead of through it. I strongly suggest a fan shroud if you don’t have one, and if you have a mechanical fan, you want it to be at least 50% of the blade width into the shroud. Another area that causes heating concerns is ignition timing, in particular a lack of vacuum advance can be particularly problematic. Proper ignition timing is required to get the engine to operate efficiently and that has a massive influence on operating temperatures.

[@robertclymer6948]

Hello Walter! Thanks as always for your in Depth analysis. I have a mild build Ford 460 BB in my 67 Mustang Gt. I run a 180 deg thermostat, alum 2 row radiator, flex fan, alum fan shroud and two 10 in pusher fans. Why does my engine push coolant to my small puke tank around 185 deg? Is the culprit my radiator cap? Have put a few different one on including the Moroso 19-21 lb and down to 7lbs and now going to try a Stant 10lb. Thanks for any feed back. I realize the cap psi effects boiling points but I rarely exceed 185 deg engine temp.

[@TheGT350Garage]

If you’re pushing coolant, something is amiss. It may just be that your water pump is creating so much pressure behind the thermostat that when it opens the surgeon coolant is overwhelming the caps. If you’re running stock pulley ratios, a high flow pump, and a high flow thermostat, this is entirely possible. To that end I would check that the bypass hose is at temp with the thermostat and flowing coolant. Also, your heater should be at temp and if you have a factory style heater control valve like an air conditioned car would, remove it as a test. Both the bypass and heater are needed for flow control, especially with high flow pumps. As for the cap, a 13-16psi cap for an 85-95 Mustang or F-Series should be ideal for a recovery system where the hose is pulling coolant off the bottom of the overflow tank to prevent air from entering the system during cool off.

[@09ThunderOne]

Just got started working on a 1966 V8 mustang convertible that's been sitting for 21 years. Dumped fuel, changed oil, rebuilt carburetor, replace condenser and points, finally got it running. Water dripping from overflow tube at top of rad. Ordered a 192 degree tstat hoping that fixes it but we'll see. Just working through it in steps.

[@TheGT350Garage]

Coolant from the radiator overflow tube can be from overheating, and a 192° thermostat is the right choice, but there could be some other contributing factors.

[@JStartin]

Appreciate the video, really informative to help understand how the system should work when fully functional. Had my ‘67 289 ‘overheat’ yesterday - gauge was showing hot and it was puking coolant out of the expansion pipe, so I need to figure out what’s going on there. Armed with this video, I feel a bit better equipped to do so!

[@TheGT350Garage]

Keep in mind, it’s a system. You may need to address a couple of things. If you have any specific questions, shoot me an email.

[@kevinhagberg1648]

Im in the same situation. Except I just changed my T-stat to 160 when I preemptivly cleaned the cooling system. I inherited My 66 & it has been sitting for a few years. im getting it back on the road. I will be changing out to higher degree T-stat and see if she still pukes coolant in this So Cal heat .

[@TheGT350Garage]

Make sure the timing is correctly set. Initial should be about 10-14°, total mechanical advance without vacuum advance should be 32-34° and the vacuum advance should add 10-14° when connected to manifold vacuum of 16-20In/hg at idle. Proper ignition timing for this modern fuel is crucial in our vintage engines.

[@keebler32ify]

🎯Thanks Boss!

[@carmenmarieg]

Hi guy thank you for educating me about the thermostat, I have a hi po 289 in my 66 mustang, freshly rebuilt, but I run hop ,so I'm running a 160 thermostat which I will change, and a 13 lbs radiator cap,is cap ok,or change it too?

[@TheGT350Garage]

You’re probably fine with the 13lb cap. Make sure you’re using vacuum advance and your timing is set up correctly as well.

[@johnbray566]

Hey just wondered if I understood it right. I have a 66 mustang 302 block and 289 heads wild cam and a sniper efi, I have a bigger 67 radiator and dual electric fans. I have either a 160 or 180 degree thermostat in it right now. Temp seems to be consistently at 195/ around what I set it to kick on at. Would it be beneficial to swap over to a higher thermostat ? Or would the constant flow mean I’m still maintaining temperature and not boiling the coolant ?

[@TheGT350Garage]

If you can maintain right around 195-205°F year round with a 180 using an electric fan you’ll be fine. But to do so, you’ll have to run the fan more than with a 195 and maintain 200-210°F. Cooler isn’t always better.

[@paulleonard2211]

Great video. What do you recommend for a radiator cap pressure. 65 mustang 289. Thank you.

[@TheGT350Garage]

Stock is 13psi, but I typically run a 16psi cap from an ‘85-‘95 Mustang 5.0L V8. If you connect your overflow hose to the bottom of your catch can you will also have a recovery type system at that point and that helps prevent overheating further by eliminating any excess air in the cooling system. It’s a very effective upgrade.

[@nicks.9287]

Hi Walter - great videos. I have a 351W fresh rebuild mild ... stock rad and fan always had the gauge above half and often close to the danger levels where I had to pull over. 180 or 190 stock type thermostat. Changed to aluminum rad 2 core, 6 blade fan with thermal clutch. Car now seems to be happy to run at about the 1/4 mark and rarely goes above half mark on the gauge. I put a temp gun on the thermostat housing, pipes, and the top tank of rad. All read about 190ish. Do you think my gauge is just messed up?

[@TheGT350Garage]

The stock gauge relies on good ground circuits. If the ground on for the instrument cluster, the ground strap from the engine to the firewall, the ground from the engine to the battery, the battery to body ground have resistance they will all affect the IVR on the back of the cluster and cause high readings. The sensor needs to have minimal Teflon tape or sealant on its threads or it will skew the readings low. It’s a simple gauge system, the service manual has electrical specs for the different areas of the system to verify. Just know that in the sensor circuit, as resistance goes up temp readings go down, in the IVR ground circuit and resistance increases so does the temperature reading. The IVR should be right around 5 volts to the gauge with battery voltage between 12.4-12.6v (engine off).

[@nicks.9287]

@@TheGT350Garage Walter, really appreciate the info. I'll double check the ground and resistance levels. I'm miffed though that the gauge would be affected by me changing the rad and fan only. Thermostat and sensor were never touched.

[@ripr7248]

Very interesting and informative video. I have a 347 monster in my 66 mustang. I'm currently running a 160 thermostat, if I was to run a 190 thermostat at what temp do I set my electric fan to operate.

[@TheGT350Garage]

It’s hard to get a big enough electric fan to cool the early cars adequately. That being said, it should turn on when the thermostat opens and turn off after the thermostat closes, so on at about 190° engine temp and off at about 175-180°. On vehicles with electric fans, I usually put the temp probe in the lower or outlet tank and adjust the temp controller to operate the fan with the coolant exchange.

[@ripr7248]

@@TheGT350Garage Makes sense, i'll give it a try Thanks for the reply

[@alecaygt]

I live in Arizona where it gets 110* in the summer till almost fall. Will this be the absolute go to ?

[@TheGT350Garage]

In really hot climates, you need to have everything pulled together, meaning the whole cooling system has to be working correctly, and capable of handling the job. The 192 thermostat is a start, a good water pump, a proper radiator, a slightly higher pressure cap, and really good coolant. In addition to a proper cooling system, the engine needs to be tuned correctly for the operating conditions. I use a vacuum advance distributor with the correct curve and with the vacuum advance operating on manifold vacuum, this is extremely important. And the carburetor needs to be tuned slightly richer in hot weather, if the engine is lean, it will generate more heat.

[@michaelpashan21]

is this the same for 67 mercury cougar? it's a 289 as well

[@TheGT350Garage]

Yes, the information in these videos is going to be true for most cars of the era, not just Mustangs.

[@dennisparass5531]

I have a 1965 Mustang fastback with A code 289 V8 and has A/C. Is your suggested Flo w Cooler 330-195 a good choice for my car ( lower HP than your car)?

[@TheGT350Garage]

If the engine is getting hot and staying hot, a 195° thermostat can help stall the coolant in the radiator to give it more time to cool off. This does require ignition timing to be correctly adjusted, with the vacuum advance operating on manifold vacuum.

[@dennisparass5531]

I purchased the thermostat you suggested. I notice a number of people suggest you drill a 1/8 inch hole in the ring to allow trapped air in the engine coolant area to escape. Do you seem any harm in doing this? Thanks for the excellent presentation.

[@TheGT350Garage]

Pay close attention to the design of the thermostat, there is already an air bleed hole built in. Also, unless the upper tank of the radiator is lower than the thermostat, a cooling system will self-bleed the first time the thermostat opens. This practice of drilling a hole was long ago addressed in thermostat design and the precautionary tale for its justification is perpetuated by a continued lack of understanding by people who just can’t grasp why it’s not needed.

[@joerothell1553]

I have a 68 mustang coup with a create 302 from Blueprint. I have no issue at all with trying to run hot while driving but when stopped it will try to run hot. As soon as you get back up to speed it will cool back off. Everything in the cooling system is new. So with that being said I have 2 questions. 1. I'm running a 180 factory style thermostat would a 195 aftermarket thermostat style help? 2. I have a factory style clutch fan on it now and before had a Flex fan on it with no change noted between the two. Both fans set close to the radiator approx. .75 inches and both were completely inside the fan shroud. I have been told that the fan should be setting a little bit outside the shroud. What's your opinion on that?

[@TheGT350Garage]

Your cooling system combination sounds like it’s capable of cooling the car, So before you change the thermostat, there’s something important you need to do. The ignition timing is likely your problem. In fact, not enough timing at idle specifically. Hopefully you have a distributor with vacuum advance, because that is one of the most important features of the distributor for controlling engine temperature. The vacuum advance should be connected to manifold vacuum. That will add timing at idle and low loads, but that timing will go away to prevent pre ignition or detonation under moderate to hard acceleration. The additional timing supports a better combustion process and allows the engine to convert the fuel to heat and pressure before the exhaust valve opens, so waste heat doesn’t build in the top of the cylinder, the combustion chamber or the exhaust port. Initial timing should be about 8-14°BTDC on a mild 302, but with the vacuum advance connected it should increase to 18-24°. This will allow less throttle opening, a leaner idle setting and still provides a good steady idle. It also reduces or cures engine run-on or dieseling. The mechanical timing curve should also be checked. For that you need a timing light with a dial or timing tape on your balancer. You need to check the timing with the vacuum advance disconnected at 500rpm increments from 1000rpm until it stops advancing (that can be 4500+rpm with factory distributors). From there you can use the information in my distributor curve video to change the springs and the total advance in order to keep the mechanical timing advance from exceeding 32-36° on your engine. I’ve seen this countless times since I started working on these cars and in the late 1980s, and ignition timing has become a more and more overlooked cause of heating issues. Give this a try, I think you’ll find it resolves your idle and low speed temperature concerns.

[@joerothell1553]

Thanks for the help. I ordered the motor with Holley EFI already installed. Due to issues with the EFI I changed back to Holley carb. The timing looked good with the light, and it was still aligned with the witness mark from when the engine was run on a dyno. What I did find is that the vacuum advance was hooked to the ported vacuum port on the carb so at idle there was no vacuum. I moved it to manifold vacuum, Well then, the timing was too far advanced, but I was not able to adjust it out, so I have ordered a new vacuum advance for the distributor. Ill comment back with the results after I get that replaced.

[@TheGT350Garage]

If the initial timing is set to 10° and the vacuum advance gives an additional 15° at idle, that’s ok. The engine should run fine with high timing at idle. Remember, manifold vacuum goes away under throttle, so the harder you accelerate the less vacuum advance timing you will have. Ideally you want intersecting timing curves that produce a 3 dimensional timing “map” from the mechanical and vacuum advance when you plot them based on engine speed and engine load (a value based on manifold vacuum). I have a timing video in the works and I’ll be posting it in a couple days, it will explain this in greater detail.

[@jackieross3831]

Thank you for clearing up the temperature issue I thought I was running too hard recently purchased a 66 Mustang 289 and was afraid of hurting it by running that 200°-210

[@TheGT350Garage]

You’re welcome! I have a final video coming for the cooling system series that will clear up some last pieces of the puzzle to make everything else make sense.

[@pieroramacciato9434]

Does thermostat need a hole drilled at top to bleed air bubbles? Seen this done in other vids. I did purchase thermostat you showed. I have told others on FB aboutk this series. It's well done. I hope to see a new vid of your's soon. Looks like you're more active on Instagram recently.

[@TheGT350Garage]

Do not drill a hole in a Robertshaw style high flow thermostat. Look carefully and you’ll see it has an air bleed engineered into the thermostat. Mr. Gasket high flow units do too. Install the thermostat with the hole at the top and you’re all set.

[@theo1976bbq]

What’s your opinion on thermostats that have a small 1/16” bypass hole cut into them to allow pressure to release what the t-stay is closed? Some t-stats come with this hole, or the tech cuts the hole with a drill.

[@TheGT350Garage]

The RobertShaw style I used has a small air bleed hole. That is the purpose of the hole, to allow air or steam to pass the thermostat in filling or operation. The “hole” can be a small opening, a passage with a check valve, or simply a small (1/16” to 1/8”) hole drilled prior to installation. The bleed hole always needs to be installed at the top.

[@daddyshovel7995]

I had the same question cause I have always done this in the past but if my customer checked his antifreeze and didn't squeeze the top hose to burp it air would somehow get trapped I had the 1/8in hole to the bottom I think. Getting the air out is a challenge in these fords.

[@TheGT350Garage]

It’s really not that difficult to get the air out of the system. The biggest issues are incorrectly routed heater hoses and thermostats without the hole or with the hole at the bottom.

[@cbobscountrybunker2312]

I use too use stant super stat but they sold out to motor rad. Is there any good brands still out there?

[@TheGT350Garage]

I like the Robertshaw which is made by Flowkooler now, also the Mr Gasket high flow. Both continue to be reliable and good options.

[@matthewenriquez8938]

Really liked your video, I have a 72 Gran Torino with a 351w I had a stock 195 thermostat and I kept climbing in temps when idling in traffic for 20 minutes as high as 220 but to be fair it was 95-98 degrees out. I got a 7 blade fan 4 row aluminum radiator and a high floor water pump and changed out that oem 195 t stat for a 180 hasn’t been turned on yet because now I’m chasing a low voltage problem but do you think I should be fine with that 180 thermostat in traffic now? I’m in the west it’s been hot recently 100 tops.

[@matthewenriquez8938]

Wait actually I forgot I drove with my new four row aluminum radiator and $ blade fan and it would still get hot so I was down to water pump and thermostat

[@TheGT350Garage]

The final piece of the puzzle is ignition timing. The engine needs proper timing to maintain cool operating temperatures. Vacuum advance on manifold vacuum, set up for 10-14°, initial timing at 10-14° BTDC, and mechanical advance set up for 20° with peak timing achieved 200-500rpm above your typical cruise rpm. That will give you 30-34° of mechanical advance under load (hard acceleration). Around town under light throttle the vacuum advance should keep the timing in the low to mid 20s at idle and high 20s to low 40s with strong manifold vacuum at typical cruise speeds. Unless you’ve done some engine work, a factory spec 351W from 1972 has a lot of quench area and doesn’t generate the turbulence in the chamber near TDC that gives the best (most ideal) combustion. With stock pistons, gaskets, and heads, these engines can be a little finicky to get right, so rely on the vacuum advance as much as you can to help you. Also, don’t take the mixture too lean, peak your vacuum at idle with the idle screws using a vacuum gauge, then back the screws out evenly until the idle vacuum falls 1-2” of vacuum. Basic tuning can make the difference when other parts of the cooling system aren’t working.

[@matthewenriquez8938]

@@TheGT350Garage the engine was rebuilt as in new everything just oem gasket bolts and all and the previous owner threw in a “mild cam” I don’t know what cam, hei distributor and summit 600 vacuum secondary electric choke carb. I don’t know anything about vacuum and I don’t really have any trusted shops near me so let me get back to you on that hahah. I learned on a 97 4.6 4v dohc teksid block I know how to do timing on that but these carbs I’m still learning(:

[@matthewenriquez8938]

@@TheGT350Garage thanks for pointing me in the right direction, I’ve taken it to a few shops and they’ve said the car was good but it clearly wasn’t; stopped going after they wanted to charge me 1,300 for a radiator change lol did it under 500

[@TheGT350Garage]

The HEI style distributor makes changing the curve very easy, you just remove the cap and rotor to access the advance mechanism and use GM advance curve parts. The vacuum advance should be adjustable and if it’s not, again, it’s just a GM HEI unit you can easily and affordably acquire from multiple sources. Using a timing light to adjust ignition advance is easy, unlike timing the ignition system or the cams in a ‘90s 4.6 DOHC Modular. All in all you should be able to address the timing in about an hour even with adjusting things.

[@ford8467]

Hi i am from Canada, where would i be able to buy that 195 thermastat.

[@TheGT350Garage]

Any major parts retailer should be able to provide one, if not, I would suggest mail order via Summit, Jegs, Rockauto here in the states (I know they tax you guys to death at the border).

[@PabloEscobar-rz7zw]

My mustang 2017 V6 cylinder head temperature goes to 225 to 226 Fahrenheit in GCC is it normal ?

[@TheGT350Garage]

That’s a perfectly normal operating temperature for a 3.7L V6.

[@jovanistreety6565]

Will this work for my 1965 mustang with a 347 stroker?

[@TheGT350Garage]

Absolutely! But you need to make sure the rest of the cooling system is in good shape and up to the task, meaning, proper radiator selection, fan and shroud for maximum airflow through the radiator, the water pump needs to do it’s part. The final key to it all is making sure the timing curve is set properly for the engines needs at wide open throttle and that the vacuum advance is running on manifold vacuum so that it adds timing at idle and part throttle cruise speeds to reduce cylinder temperature.

[@danielnavarro6194]

Hello. Sorry to bother with a question I'm sure you've been asked over and over. I tried going through all the comments and must of missed my particular setup. What thermostat do you recommend for a stock 289/302 with pertronix distributor? I think I read somewhere a robert shaw 330-195, not a 100% on that, if so what on/off switch should I go with for the electric fans? Engine is completely rebuild, all new hoses, with 3 row aluminum radiator, with 16" electric fan, Currently have a new 160 thermostat and 160/140 kick on switch, but on one recent occasion thermostat housing got hot it started to melt the paint on the thermostat housing. I think I read that the distributor comes with 24 advanced timing springs already in. Should I change those as well?? I have timing set at 10 degree btdc. its an automatic, running at 975 rpms on idle and 725 in gear. Not sure what other info you'd need. Any help would be greatly appreciated. Thank you!!

[@TheGT350Garage]

Too cool a thermostat will cause the engine to go into an uncontrolled thermal cycle where it doesn’t cool down unless it gets shut off, and that sounds like what you were experiencing with the 160°F unit installed. The 330-195 thermostat is correct. Look carefully and it has a vent hole that needs to be installed up (top) to bleed air into the radiator. If your manifold has a recess for the thermostat use a flat thermometer housing, if the manifold is flat use a recessed housing, one of the major reasons for thermostat housing leaks is sandwiching the thermostat between a flat housing and a flat manifold. Use Permatex ultra grey sparingly on the gasket, a smear is adequate, it should not ooze sealant when tightened up. I’ve always used the basic Flex-A-Lite thermostatic controller (under $30), it’s basic but effective and reliable when used to power on a 20A or 30A relay. Summit has two units from Davies Craig that are promising in the $75-85 range that seem to be digitally programmable and include replaceable relays, it all depends on your budget and how fancy you want to get, there are some really nice controllers available these days. Install the temp probe directly into the lower tank in place of the drain or use a probe adapter with the lower coolant hose to slip it into the cooling system there for best results. Set the “on” temp about 10-20°F below the thermostat temp, so 175-185°F. With the probe in the lower tank location it will catch the cycle of coolant through the radiator as the hot engine coolant exchanges with the cool and start taking heat out of the coolant for the next cycle of the thermostat. As for the ignition timing, if you can change the limiter bushing in your distributor to a 20° advance limit and increase initial timing to 12-14° the engine will run cooler. If you have springs to change the rate of advance, full advance should occur 200-400rpm above your average cruising rpm in high gear. Also be sure to use vacuum advance on a manifold vacuum source, full vacuum should add 10-12° of timing with the engine under light loads but then it will “go away” as vacuum decreases when you accelerating and the engine is working harder, letting the engine run on the mechanical advance curve as it should. Proper use of vacuum advance with the correct timing curve can help the engine operate with a more stable idle and with a leaner air/fuel mixture at idle and under light loads, which actually contributes to cooler engine operation by completing combustion in the chamber before the exhaust valve opens.

[@danielnavarro6194]

@@TheGT350Garage Hello. I feel that is what is going on in my situation, uncontrolled thermal cycle. First time I took it out for a test drive after rebuilding the engine, it had a nice pick up to it. I was really impressed with the way it drove, considering it was almost completely stock. But after that first test drive, I just couldn't replicate that same power. I guess by that point it was already running hot, and now I'm guessing that is why I always have a hard time restarting it after it warms up. When cold, it'll crank on with the first start. When warm, it takes a few cranks. As for the ignition timing, I opened up the distributor today and it only had a pair of silver springs. It didn't have and limiter bushings. I am assuming the the 24 degrees that they come preset with is the maximum degrees the distributor allows? I'm guessing... Luckily, I saved the limiter bushings and springs. So, I will install the 10/10=20 degree limiter bushings, but which springs should I use?? It has a copper set, black set, and what is on it now a silver set of springs. I read somewhere that the copper springs will get to the 20 degrees the quickest. Not sure if that is the recommended for my application or if you would run something different for better results. Also, mentioned something about a magnetic lock out tab, but I don't think that applies to my application, cause it mentions not using any springs or limiters if using the lock out. Sorry for my ignorance to all this, still learning about all this. I forgot to mention, I live in South Texas, where it is 100+ degrees almost year round. So, not sure if that changes anything. Also, not sure if running the heater core is good or bad for trying to keep the engine cool. I will make all the necessary changes here in the next week or two, as soon as I order everything. Ill wait to see if you recommend anything different. Ill let you know how everything goes. I am extremely grateful for your time and all the info you have provided me. Thank you

[@TheGT350Garage]

@danielnavarro6194 use the #10 20° limiter and combine a silver and copper spring to get your curve in about 3000rpm.

[@danielnavarro6194]

@@TheGT350Garage Got it. Just be sure I understood that correctly. I will use one silver spring and one copper spring, does it matter which side each color spring is placed in? Thank you

[@TheGT350Garage]

@danielnavarro6194 doesn’t matter which side, it’s about the total tension, you’re splitting the difference between the slower silver pair and the faster copper colored pair.

[@tomrose6292]

Late model race cars use a flat block off plate with a 11/16 hole.but they usually keep their rpms at a high level

[@TheGT350Garage]

Race cars and street cars are entirely different animals. You can restrict flow for a steady(ish) state application and be ok. But the wide variation in operating conditions on a street car don’t allow for a fixed orifice restriction.

[@tomrose6292]

@@TheGT350Garage yea that's what my buddy was telling me when I saw him put that plate in..

[@davidc.249]

What thermostat would you recommend for a 1985 f150 with a 351 windsor I currently have a 180

[@TheGT350Garage]

The 192-195° thermostat is still the best choice. The larger radiator capacity on the truck will be an asset as well. Just make sure you have good airflow through the radiator core and you’re in good shape.

[@davidc.249]

@@TheGT350Garage I have a new aluminum 3 row radiator running waterless coolant

[@TheGT350Garage]

Should be fine. What the OE 3-row lacks in tube area it makes up for in raw surface area in a truck application. I never found a significant enough benefit from waterless coolant to justify the expense. Like any coolant, the additive package will deplete over time and it will require replacement. The ELC coolants I suggest are good for 8 years in OTR Trucking applications and are honestly 10-12 year coolants for limited use passenger vehicles. That said, there’s nothing wrong with your choice, as it’s light years better than any of the green coolant formulations on the market.

[@cplrecon]

Where did you get the Thermostat?

[@TheGT350Garage]

The genuine “Robertshaw” thermostats are manufactured by Flowcooler and available through Summit Racing and other aftermarket parts vendors.

[@cplrecon]

@@TheGT350Garage Awesome! Is that where you got the water pump too? Thank you!

[@TheGT350Garage]

I’ll be covering that in the video addressing water pumps in a few days.

[@cplrecon]

@@TheGT350Garage awesome!

[@ksacky]

You forgot to mention that engine oil also cools the engine

[@TheGT350Garage]

That engine oil is a secondary form of cooling is only partly true. This thought process comes from air cooled engines, where only oil circulars through the engine fans it distributes quite a bit of heat, but water cooled engines are different in that the oil does not get as hot and once the oil reaches operating temperatures it isn’t cooling, it’s only lubricating. If you run a Hayden sandwich style oil to water heat exchanger like the SSP Mustangs of the ‘80s, the coolant initially warms the oil and later cools the oil, but that heat then has to go through the cooling system. And if you install an oil-to-air oil cooler and place it in front of the radiator the heat it extracts passes through the radiator reducing the radiators efficiency. Everything has compromises and trade offs, and the thermal management on these cars requires being thoughtful about it.

[@Faith0929ROK]

Nice video, I disagree. Thermostat starts open little by little before 192 or 160 or whatever you have. 192 and 160 t stat is fully opened at advertise temperature. Once your engine temp reaches 193 or 161, it’s always open.

[@TheGT350Garage]

The idea is to avoid the thermostat staying open, and the higher temp will close sooner after a heavy heat cycle that might cause it to stay open. On cars that have room for an electric fan or a thermostatic clutch fan to draw additional air at high demand the 192+ thermostat really works well to allow air conditioning on the early cars too.