How hot do Big Blocks normally run?

[SavageC20]

I have a 454 in my 72' and it gets warm in the summer (200-230) when the truck is sitting at stop lights or driving slowly (0-40mph). I am wondering if this is too hot for the engine? It has never boiled over in this situation. I have heard that big blocks run hot, but not sure what "hot" is. In the winter the temps stay around 180-190. How hot should a big block run with an ambient air temperature of 90-110 degrees? Any ideas on how to make it run cooler? I am wanting to take this truck in the mountains in the summer, but I don't think it would be able to pull a grade without getting north of 230 degrees.

The truck has a new 4 row stock style radiator from LMC, new stock water pump, new thermostat, stock fan and fan shroud, new fan clutch, 16lb radiator cap, 50/50 coolant mix, and the cooling system is clean. Temperature probe is located in the intake manifold near the thermostat housing, it goes to a VDO mechanical gauge. Carb is tuned properly and timing is set at 34 degrees total...vacuum advance not hooked up.

The truck still has the factory A/C condenser in front of the radiator as well as a transmission cooler in between them. This may be affecting airflow, but minus the transmission cooler this is basically how it was from the factory.

[rjs53]

I know the newer motors run around 210-220, but I always try to keep my 1st gen small and big blocks under 200 degrees. Not sure exactly how hot they can run though without overheating.

[geezer#99]

I rode in a 70 Vette in Reno back 30 years ago. The gauge hit 245. It was nerve racking.
With 34 total timing there’s a chance you only have 8 initial.
More initial will help it run cooler.
You could try plugging your vac advance back up to a manifold vac source.

[SavageC20]

Originally Posted by geezer#99

I rode in a 70 Vette in Reno back 30 years ago. The gauge hit 245. It was nerve racking.
With 34 total timing there’s a chance you only have 8 initial.
More initial will help it run cooler.
You could try plugging your vac advance back up to a manifold vac source.

I should have listed the initial timing as well. I have it set at 12 or 14 degrees I believe.

I was running the vacuum advance and it didn't change anything.

[geezer#99]

So that means you have 20 in the distributor.
Maybe!
At what rpm is your timing all in?

[SavageC20]

Originally Posted by geezer#99

So that means you have 20 in the distributor.
Maybe!
At what rpm is your timing all in?

No idea to be honest. I had my machine shop break in the engine so I would have no liability if anything went south. They set the timing during this process. I know on the invoice it said 34 total, but I don't have the invoice in front of me to be sure of the exact initial timing so I am going off memory....

[Mike C]

Here is a link to a thread that will help you. There are more. Lars on the CorvetteForum is great and and this thread has a copied article from John Hinckley. Too much to retype here.

https://www.corvetteforum.com/forums...heating-2.html

[72c20customcamper]

My BBC runs at 190 most times but my fans come on at 195 most time it's when I'm in traffic. These are head temps if your running that hot at the manifold it's too hot . New engines are designed to run hot to help emissions. If you have a thermo clutch check it it's possible it's not coming on .

[SavageC20]

Originally Posted by 72c20customcamper

My BBC runs at 190 most times but my fans come on at 195 most time it's when I'm in traffic. These are head temps if your running that hot at the manifold it's too hot . New engines are designed to run hot to help emissions. If you have a thermo clutch check it it's possible it's not coming on .

I have a new fan clutch that is functioning properly, but it is the standard duty variant. I have thought about getting a heavy duty or severe duty...do you think that would help?
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[custom10nut]

That sounds about right. Your thermostat temp only determines when it opens during the warm up. Many don’t understand that putting Coolant in your water raises the boiling point to around 225 deg, then put the system under pressure and it past 240 deg. Also as the fluid gets hot it expands, and that why we have the “overflow” tank.
A four core radiator and electric fan will help you while you’re in traffic.
I was having sort of the same issue with my 350, and summized that the clutch on the fan was working correctly, so I went to a “no-clutch fan, and the issue went away.
I’m not trying to insult anyone’s intelligence, but some just don’t know.

[engineer_gregh]

Thats too hot IMO. My 402 is bored .30 over and I had the same problem as you. I added two 1600 CFM electric pusher fans on a stock 4 row radiator that kick on at 185 and off at 165, solved my problem. Mine don't get above ~190 even in the summer with the A/C on. No more mechanical fan for me.

[72c20customcamper]

Originally Posted by SavageC20

I have a new fan clutch that is functioning properly, but it is the standard duty variant. I have thought about getting a heavy duty or severe duty...do you think that would help?
Posted via Mobile Device

Does your truck have a long or short water pump. My chevelle has a short and from what I have seen there is no HD version . I went from a stock clutch fan to a 7 blade direct drive. Still ran hot. I put a DeWitt HP series in with dual electric spall fans . Car can idle indefinitely in 95° weather. Used to heat up coming off highway speed it does climp a little but the fans kick in and it goes right down to 185.
I'm running a mark Jones 467 .

[Steeveedee]

I have a 180° thermostat, but pulling a hill with my travel trailer the engine has gotten up to 260°, which is about as hot as would be allowed.. It helps that there is no air in the system and I had a good cap. I don't like it, and went to a truly heavy duty fan clutch, but haven't taken the trailer out for a camp out since I put that clutch on.

[weq92f]

Originally Posted by engineer_gregh

Thats too hot IMO. My 402 is bored .30 over and I had the same problem as you. I added two 1600 CFM electric pusher fans on a stock 4 row radiator that kick on at 185 and off at 165, solved my problem. Mine don't get above ~190 even in the summer with the A/C on. No more mechanical fan for me.

I'm interested to know where your senders are located for the fans/gauge, what therm-o you run.

I have my fan sender in the therm-o housing and the gauge sender in the intake right at the driver head... gauge hangs around 200-210 on hot day at idle with AC blowing and fans running. Fans are set to on=195 off=185. Must be about 10* diff between these two senders or their locations.

-klb

[toolboxchev]

Couple of things, first verify actual temp by using an infared laser thermometer.

Second, every auto parts junk warehouse call sell you a temp sending unit for the incorrect application. If you use a modern unit for a later year which, will fit, will work, yet give you incorrect readings. If its sending the wrong electronic information to the gauge you will get screwy readings.

Thermostats specs vary greatly by manufacturer, I am using a premium Stant 180 degree Stainless unit. Their regular stuff is junk, stay away from the fail safe design. It works and then clicks and stays open not allowing the coolant to pick up the heat and transfer it out to the radiator.

Using the correct radiator cap for your setup matter a ton also. Pressurized at 16lb cap with reservoir is what I like. I can see a 10-15 degree temp drop when running the heater.

On a final note, the spark advance at idle, for a street machine is preferred for my purposes. Try an adjustable vac advance from Pertronix and dial it to your engines needs with a timing light and vac guage. You would also have to take into consideration what type of cam you had installed. Some cam profiles do not produce much vac at idle.

When you have the wrong combination of these things the entire system will act like a heat soak. Another words when its starts to get warm, it will get hot due in part to incorrect A/F ratios, timing, lack of intial advance and so forth. Tuning skills really help here.

Todays Ethanol fuels like more intial advance, due to chemistry. And Warmer temps to burn completely.

All my fans are stock, no clutches, no electric fans, stock, stock, stock.

[72c20customcamper]

Originally Posted by Steeveedee

I have a 180° thermostat, but pulling a hill with my travel trailer the engine has gotten up to 260°, which is about as hot as would be allowed.. It helps that there is no air in the system and I had a good cap. I don't like it, and went to a truly heavy duty fan clutch, but haven't taken the trailer out for a camp out since I put that clutch on.

I have a 160° I also drilled two 1/16 th bypass holes to help burp the cooling system. But once the stat opens up all the way dont matter. Never use the car when it's cold.

[72c20customcamper]

Originally Posted by Steeveedee

I have a 180° thermostat, but pulling a hill with my travel trailer the engine has gotten up to 260°, which is about as hot as would be allowed.. It helps that there is no air in the system and I had a good cap. I don't like it, and went to a truly heavy duty fan clutch, but haven't taken the trailer out for a camp out since I put that clutch on.

Originally Posted by weq92f

I'm interested to know where your senders are located for the fans/gauge, what therm-o you run.

I have my fan sender in the therm-o housing and the gauge sender in the intake right at the driver head... gauge hangs around 200-210 on hot day at idle with AC blowing and fans running. Fans are set to on=195 off=185. Must be about 10* diff between these two senders or their locations.

-klb

I use a mechanical temp gauge in the head . The sensor is in my radiator for the fans only one ,it grounds at 195 and starts the fans and opens at 185 stopping the fans .

There is a 10 to 15° difference between head temps and temp of the water. So if your running 200 -210 at the water housing in the manifold your head temp will be much higher.

My fans kick on when the head temp reaches 205. But the water temp measured buy both an instant read thermopen and a thermoworks infrared themo is 195.

[Steeveedee]

My temp gauge is manual, with the bulb in the head. I know from long standing experience that 260F won't kill a BBC quickly. But I still don't like it, of course. It just tends to age the equipment faster than I like. It's up for rebuild, anyway. It's been 110k miles since the last rebuild, is using oil, and the pressure drops to 20 PSI when it's good and hot.

[clay68c10]

I'd say you're running a bit warm. If you had operational AC, I bet it would put you over the edge. Same with pulling a grade.
My previous 68 had a 030 over 454, 195 stat, and a Lincoln MK8 electric fan. It would hold steady at 200-205 in TX summer with the AC on and in traffic.
I think the fan was the key for me.

[RustyBucket]

My 2wd Blazer has a mild 454 +.40, 236 peanut port heads, Performer RPM, headers... and runs COOL. Idling a long time on a hot Florida day it won't go over 190deg. At road speed it drops back down to 160. Factory gauge with the sender in the intake. It has a 4 core GM radiator, factory shroud, 7 blade clutch fan, aluminum water pump and an A/C condenser in front of the radiator(don't use the A/C 'cause I never put the top on). I haven't had a timing light on it in years but it seems to run best advanced 'til it bucks against the starter and backed off a little.

[SavageC20]

Originally Posted by 72c20customcamper

Does your truck have a long or short water pump. My chevelle has a short and from what I have seen there is no HD version . I went from a stock clutch fan to a 7 blade direct drive. Still ran hot. I put a DeWitt HP series in with dual electric spall fans . Car can idle indefinitely in 95° weather. Used to heat up coming off highway speed it does climp a little but the fans kick in and it goes right down to 185.
I'm running a mark Jones 467 .

I have the short water pump. This is the exact problem I have been running into when searching for a severe duty fan clutch for the short pump. I am going to mess with my stock system first and see if I can get it to work right, but if I can't I will convert to electric fans.

[WorkinLonghorn]

SavageC20, you need to hook up that vacuum advance. You are running around with a severely retarded ignition at part throttle loads. This WILL cause extra heat. If you didn't notice a difference with it hooked up, then maybe the diaphragm is broken or the vacuum source is plugged or the wrong one.
Take a hose and hook it up to the distributor vacuum advance port ( the one on the distrib.)and test it to see if it holds vacuum. Just use your mouth. Take off the cap and see if there is movement when vacuum is applied. Then hook up the hose to the correct vacuum port on the carb (metered vacuum = no vacuum at idle, some vacuum at part throttle only) to see if you get vacuum there at part throttle.

Sometime you don't notice a difference but believe me, you need vacuum advance.

This is really a "no brainer" and I am surprised that no one is seeing this.

Did you know that the stock vacuum advance for a 396 adds 15° advance at part throttle only?

[Mike C]

Originally Posted by WorkinLonghorn

SavageC20, you need to hook up that vacuum advance. You are running around with a severely retarded ignition at part throttle loads. This WILL cause extra heat. If you didn't notice a difference with it hooked up, then maybe the diaphragm is broken or the vacuum source is plugged or the wrong one.
Take a hose and hook it up to the distributor vacuum advance port ( the one on the distrib.)and test it to see if it holds vacuum. Just use your mouth. Take off the cap and see if there is movement when vacuum is applied. Then hook up the hose to the correct vacuum port on the carb (metered vacuum = no vacuum at idle, some vacuum at part throttle only) to see if you get vacuum there at part throttle.

Sometime you don't notice a difference but believe me, you need vacuum advance.

This is really a "no brainer" and I am surprised that no one is seeing this.

Did you know that the stock vacuum advance for a 396 adds 15° advance at part throttle only?

If only they had gone to my link above in post #7 they would have seen that much sooner. LOL.

Big block Corvettes run notoriously hot and those guys have the answer that can be applied to a truck. But as I noted above, the correct process is too long to retype all the darn time. Thus the link.

[SavageC20]

Originally Posted by WorkinLonghorn

SavageC20, you need to hook up that vacuum advance. You are running around with a severely retarded ignition at part throttle loads. This WILL cause extra heat. If you didn't notice a difference with it hooked up, then maybe the diaphragm is broken or the vacuum source is plugged or the wrong one.
Take a hose and hook it up to the distributor vacuum advance port ( the one on the distrib.)and test it to see if it holds vacuum. Just use your mouth. Take off the cap and see if there is movement when vacuum is applied. Then hook up the hose to the correct vacuum port on the carb (metered vacuum = no vacuum at idle, some vacuum at part throttle only) to see if you get vacuum there at part throttle.

Sometime you don't notice a difference but believe me, you need vacuum advance.

This is really a "no brainer" and I am surprised that no one is seeing this.

Did you know that the stock vacuum advance for a 396 adds 15° advance at part throttle only?

Thank you for the advice.
The reason I disconnected it is because the guy that tuned it at the machine shop said not to run it. I trusted his judgement, but I will hook it back up and see if it changes anything.
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[alsriv2]

My BB396 was built professionally 7 years ago. (Shown in profile picture) We finally got the truck up and running just last year after much work. The truck has a 3 core radiator, a fixed fan with no shroud and always runs cool, even here in the SE Arizona desert. The heads are from a '71 402, meaning they are not the small peanut port heads. We actually had to add a 180 thermostat as the Holley Sniper control system did not like the cool temps. It was nothing to see the truck at 80mph/3000rpm stay cool at 160deg. The Holley system is a bit happier now, but the TQ converter is all wrong for the Cam installed. That will be the next item I have to fix. I wish I could give better details on timing and such, but we have it set for the builders dyno setup at 34 all in. Per the builder, I am NOT running vacuum advance, we are running a full MSD ignition that is also tied into the Sniper control system. TO say that I am happy after 7 years of pain would be an understatement.