The Stovebolt Site Forums The Shop Area Engine Shop Chev 350 sb Temperature

Can someone tell me what temperature a small block Chev 350 should be running at. I have put a 160 and 180 thermastat in it and in both cases it is running about 200.

Waggy,

I think 180&deg is a perfect temperature for this engine. From what you are saying, it appears you have some cooling issues. My first thought would be a plugged radiator. Excess advance timing will make it run at a higher temp too, but this is usually accompanied with some pre-ignition so you might hear it. Can you look into the radiator fill and see if the tubes are scaled shut?

Stuart

Excess heat is more likely to come from too little advance than too much. If you have too much advance, it is more likely that it will ping so badly that you wouldn't want to drive it or that it would fight the starter bad enough to make starting difficult before it ever overheated. In what vehicle is the 350? If it is in a truck in which a V8 was an option, the answer to your cooling problem could be different than if it was in a AD, for instance. Actually, you may not have a problem if it doesn't go much above 200, but it would be better to have the cooling system able to keep it near the thermostat setting.

It,s probably just the gauge out of callibration. If it runs the same temp when its hot or cold out it is just the gauge. If it gets hot only in hot weather, on a hard pull, or slow traffic you might have a problem. How much pressure do you run?

It may be the gauge as has been suggested. Try a new one. However if it is not, then radiator with not enough rows, such as from a six cylinder would not have enough cooling. Also warped heads will also cause heating. Had that happen before on a slant six with a new radiator and thermostat and such. This is not common but have known the water impellar inside the water pump to slip and not turn at the proper speed hence the anti freeze not traveling fast enough through the engine and radiator. Have seen a pump that did that. Wierd! Collapsed or crimped radiator hoses ( had that happen too ). When cold the hose looked normal but when hot it would collapse causing the anti freeze to stop circulating. Bad fan clutch if you have one. Had that MORE than once. Had defective thermostats. Running too lean can do this. Baldy is right. I had a Chevy 230 six jump timing on my 68 Chevelle. The distributor clamp bolt was loose, and the exhaust manifold got "Cherry Red" then would not run from retarded timing. Had to let it cool before fixing it. Can burn out your valves that way rather quickly. It happened back east at -14* in the winter on my way to my brothers place. I reset the timing and it was fine after that. No thermostat ( I know you have one ), can cause it to overheat because the coolant can go through the radiator too fast and not get cooled enough before its back into the engine again. Known of that before. Wrong heat range on the plugs can cause overheating but not usually but worth a look see. You may have too hot a spark plug. Go to a cooler one. After nearly working on rigs on and off for about 41 years you run into or seen most everything. I would get some Redline stuff called Water Wetter. Its irridescent red in color. Get about 2 bottles. Prestone makes basically the same stuff. Its bright green in color. It helps your antifreeze cool faster as it goes through the radiator. I used it here in southern Oregon where the summers get hot. 90's too over 100*. Works great! May need a third bottle if you have a 4 row radiator. Not a gimmick. I have it in both my rigs and it works great. One last resort. They do make a high performance aluminum water pump. It may be worth the extra $$ to get one. They work and are recommended for high performance engines for max cooling. About 30% more effective. 180 is the best for non computerized rigs. Check radiator circulation. If it moves slowly across the top of the radiator then have it fixed or replaced. I hope this info helps. Henry

engine temp has more to do with the setup than the particular engine - the first thing to try is a check in the rad with a good thermometer [don't let yer wife find out] to see how the gauge relates to reality .... next is to check the distance of the fan from the rad - you don't say what the engine is in .... have a shroud?

I wouldn't say there's a real problem at 200 until you've analyzed your installation, it'd be a cold day when a small block stays at 180

Bill

Nothing wrong with a 350 running at 200. That's well below where your oil starts breaking down. Many computer controlled motors run that or hotter.

My newest 350 runs consistently at 200 and up to 212 or so when in stop and go traffic. I checked the owners manual and visited a web site that deals with computer controlled motors. Its fine.

Somewhere above 220 is where the oil gets in trouble and provided the motor is otherwise healthy that's where you start to worry.

We really need more info about your motor and application before responding to this one. Unless it has always run at 180 and suddenly now runs 200 I wouldn't worry about it.

These are all valid thoughts. My only concern would be the fact that the engine doesn't respond to the rating of the installed thermostat. If the cooling system is functioning as it should, and you install a 180&deg thermostat, that is the approximate temperature the engine should operate at under normal running conditions

If you try several thermostats of differing temps, and the systems doesn't respond, my first thought would be that the prime cooler...the radiator, doesn't have the ability to cool properly, and at some point, you are going to find this out the hard way. If the rating of the installed thermostat doesn't regulate the operating temp of the engine, what does?

Stuart

Mr. Gasket makes thermostats that open within 2 degrees of the rating. I have one in my truck and it works great!. Does not climb way up to open like the others do.

the idea that a 180 thermostat should keep the engine at 180 is wrong ... the thermostat simply controls the minimum temp for water circulation to prevent an engine running too cold - it doesn't open until the water is 180, then the water can move thru the rad and get cooled - if the engine tends to run cooler or the cooling system is overkill, then the water is cooled faster than the engine heats it and the thermostat may start to close again - under those conditions the temp will hover around 180, but small blocks "like" to run hotter ... what regulates the maximum temp of the engine is the design of the engine, my 235's have consistently run cool, needing a 180 thermostat to keep the temp up, my 283 consistently runs hotter, regardless if the thermostat is a 160 or 180

aren't pressure caps used to allow water heating above what would be boiling at atmospheric pressure? if simply putting a lower rated thermostat in made the engine run cooler, why have a pressure cap?

Bill

my firebird runs 180-190 with a sbc an my 85 chevy 4x4 runs usally no hotter then 170-180 but it goes up to bout 190 when i cut it off after its been run hard

Bill,

I respectfully disagree. The thermostat is the control mechanism (the only one) for the cooling system. The radiator is designed be able to satisfy what the thermostat asks of it! A properly functioning cooling system should maintain temperature near that of the thermostat. It has no bearing on engine characteristics.

The only reason a modern automotive system runs at 212&deg is because it was designed in Detroit to run at 212&deg. If it has adequate cooling capacity and you install a 175&deg 'stat', it would probably run at that temp! That's how I see it.

Stuart

Maybe its time for another one of my cherished illusions to be destroyed.

I've always felt that, within reason, the cooler an engine runs, the longer it will last. By "within reason" I mean somewhere in the 150 to 180 range after warmup, and in normal operation. You may gain a little, thermodynamically, by having your cylinder walls 30 degrees warmer (to add heat to the air fuel charge) but I doubt that you would notice the difference.

Synthetic oils and 18 psi radiator caps seem to me to be designed to allow a car to have a better chance of surviving boundary conditions, not to improve performance. I'm sure we would all be a little upset if our engines melted down the first time we got into stop and go traffic, and the automobile manufacturers realize that. If I am not mistaken, the later model, hotter running engines are designed that way due to emissions considerations. We don't have no steenking emissions considerations, so why not run cool?

The 350 in my late model C30 has a 13 quart oil capacity. (Seven quart pan with two 2 quart remote filters and a thermostatically controlled oil cooler set to 160 degrees.) If it ever dies I'll let you know.

T-stat rating is the minimum temp, it has no effect on temps above the opening rating. I wouldn't worry about 200, sounds about right to me. IIRC, the pressure cap raises the boiling point 3* for each pound of pressure-a 10 psi cap will raise the boiling point 30*.

Brian,

I totally agree...T-stat rating is the minimum temp, the temperature the stat opens. Once it opens, the big husky radiator cools the water, sends it back to the engine and it sits, or circulates until the T-stat opens again and the whole deal happens again. If this T-stat happens to be a 190&deg unit, the temperature of the engine and cooling system would stay, under normal conditions, around 190&deg...wouldn't it?

Provided the radiator had the capacity, and you stuck a 170&deg thermostat in, the engine and cooling system would stay, under normal conditions, around 170&deg...wouldn't it?

If a person went into a parts store intent on buying a T-stat to keep their ride at 180&deg, would they have to do a bunch of calculating to guesstimate which thermostat to buy. I don't think so, I think they would merely buy a 180&deg stat.

If your rig runs for years at, say 190&deg, and all of a sudden, it starts to overheat at the smallest pull, or the occasional hot day, the radiator is the first place you would look. It is plugging up or the fins have rotted off and it can no longer cool the water below the minimum opening temp of the stat. This is how I have always pictured it working.

Stuart

Stuart, fins rotting off? I've seen some pretty ratty looking older radiators and always figured they got in the way of a wrench. I had heard that the old header tanks were made of brass, and the fins were copper. Is that right?

starkweatherr,

I'm located on the west coast of California right smack dab on the ocean. It's very common to see radiators with tubes only...all the fin material has been eaten off. When you brush the front of the radiator with your hand, the fins magically disappear.

I have always assumed the tanks and tubes were brass or copper...whatever the fin material is doesn't do well in the salt air.

Stuart

Stuart, I guess theorectically, yes, the engine would run right near the stat temp, but in the real world they always run hotter, esp. in traffic, w/A/C, added trans heat, loads, etc. Salt air eats up everything, it just takes longer to get to the tubes & tanks as they are thicker than the fins.

We get fins rotting away here in the midwest from the salt on the streets for snow/ice removal.

They use sand(if anything,usually they use nothing)for ice here, not really very effective at all-in fact sometimes they put too much on overpasses & its actually worse, like marbles on a smooth floor

Stuart!
"The only reason a modern automotive system runs at 212° is because it was designed in Detroit to run at 212°." .... and the small block was designed to run above 180!!

a thermostat is to get the engine up to a minimum operating temp as fast as possible and make sure it doesn't fall below that, nothing else see here - if Detroit designed the engine to run at 212, it won't matter what thermostat you put in, it'll run about 212 once warmed up, and water would start circulating at the 'stats rating regardless if it were 160 or 180, 175 or 200

the cooling system ain't rocket science - running an engine too cool results in poor fuel use, acid buildups in the oil, and excessive wear - running an engine too hot results in the rad boiling over - the reason rad caps have increased in pressure ratings over the years is to allow the engine to run at a higher [designed] temp without boiling over, and the reason the 6's used a zero to 7# cap and the sbc uses a 7-15# cap is the sb runs at higher temps, altho both might have the same rated 'stat .... and I've never heard of a 200° thermostat in a small block, but they run at that temp all day long

the answer to waggy's original question is, it's better to use a 180° 'stat on a 350, and if the cooling system is in good condition, with a 12-15# cap, a 'normal' operating temp of about 200 is not a problem .... and will not be related to the 'stat temp .... but check the actual water temp to see if the gauge is accurate

Waggy,

I will amend my thinking based on some of the above posts. Changing thermostats will have absolutely no bearing on the temperature your engine runs. Engine operating temperature is a factor designed in by the engineers in Detroit and has nothing to do with your cooling system. You will have to buy a new engine that has been designed to run at a lower temperature, then the cooling system you now have will be able handle it.

The key point here is that thermostat rating and the operating temperature of the engine have nothing at all to do with each other. I quote "normal operating temp will not be related to stat temp".

EDIT. Yes, this post is pure sarcasm. :rolleyes:

Stuart

Not entirely correct, as installing a higher temp stat WILL raise normal operating temp, but a lower stat may or may not lower normal operating temp. Yes, the stat would open sooner, but it would not neccessarily lower the normal operating temp. It gets real hot down here, I've never seen a 350 in anything run 180* using a 180* stat or 195* w/a 195* stat, they always run higher. Yes, most late model cooling systems are designed to run 210*+ for emissions.
Generally speaking, if you are having an overheating problem, a lower temp stat will not help, the engine will build heat regardless of the temp of the stat opening.

Stuart - sarcasm? doesn't answer questions, Waggy doesn't indicate his cooling system "can't handle it"

a 350 running at 200 is not displaying an overheating problem, like 64fleetside sez, they run that way, and using a higher temp thermostat serves the purpose of getting them up there faster, especially with a very efficient cooling system ... but a higher rated 'stat won't necessarily raise normal operating temp, unless it's an engine that tends to run cooler then the selected temp ... like the 235 with a good original system

live in a cold climate and you'll see the difference in a 160 and 195 thermostat is that it takes longer for the heater to really pump out heat, especially with a 235 or 283, not quite as noticeable with a newer 350 .... most 350 applications use 180-195° 'stats and a 16# cap

do the new[ish] engines that normally run above 212 have 212-220° thermostats? what's the highest 'stat available?

Bill

I have one small block that runs around 200 and up to 216 today and I've seen as high as maybe 224. It is supposed to have a 195 degree thermostat but I've never opened it to find out if that is what it is or not.

Today I watched both the coolant temp and oil temp carefully out of curiosity. Outdoor temps were in the 50's and 60's today. It has digital guages making them easy to read. I assume they are also accurate, but have no way of really knowing.

Oil temp rose much slower than coolant and then mostly stayed within a couple degrees of the coolant. Both rose to about 200 until we spent a few minutes stuck in traffic, and then once there was an opening I blasted it hard a little and both went up around 220.

It took oil temp much longer to come down than the coolant and that was something I had not noticed before. It has an engine oil cooler too, so this surprised me a bit.

The car is an '85 Corvette with TPI and just over 100,000 on the original motor. Near as I can tell nothing about how it runs is unusal for one of these cars. '85 is the last full year for a cast iron small block in a Corvette and aside from the TPI and maybe the cam, this motor is basically just a Chevrolet 350.

I see no problem running 200 to 220 degrees.

I have a 1-ton pickup with a 454 that I've seen run 230+ according to a stock analog guage. That one has scared me a bit and I watch it carefully, and change the oil a little more often.

For every pound of pressure the cap has, the temp goes up 2 degrees. A 13 pound cap will bring up the radiator temp 26 degrees. A lower pressure cap has helped me in the past. A 9 lb will make it 18 degrees. Maybe this will help some. I have a 4 row high efficiency desert cooler in my full size van with a 350 and it runs about 190-195. Even with the a/c running and a new factory 195 stat. My pick up with a 350 has a 3 row standard 7 fins per inch and stay exactly 195 and barely moves when going up long hills. Its got quite a bit of scale in it and its the original 87 radiator. Its going to get a new 3 row 14 fins per inch core this week before putting in a new modified 250 inline six. Will cool almost as much as a 4 row without spending a bunch more for a 4 row and get little more cooling. Standard GM rads usually are 7 fins per inch as per the radiator shop where I get mine. More rows and more fins per inch do make a big difference in cooling power. Aluminum rads cools more effieciently and more PRICEY! A 2 row with cool like a 3 row. A 3 row aluminum should really do the trick. Brass does not cool as well as aluminum. I put a new brass radiator in my Bravada (S-10) with the 4.3L and it had a new water pump and thermostat and with the a/c running it would run hotter than I would like it. I replaced it with an aluminum and that solved my problem. I learned these things the hard way. I just hope this will help some plus with all the other suggestions posted here. Henry

In the end, the engine temperature depends on the capacity of the cooling system. At one extreme, put a 190 degree thermostat in an engine, and use a radiator from a Honda CX500 motorcycle. It won't take it long to get really hot, and it won't stay anywhere near 190 degrees.

On the other extreme, add on a radiator from one of those big emergency generators. It will take the normal amount of time for the engine to get up to 190 degrees, before the thermostat opens, but you won't be able to get the temperature to go much higher than that no matter what you do.

There are factors other than the radiator involved, but I would suggest that radiator cooling capacity is THE big factor in engine temp.

The same is true of oil coolers. A 350 with a radiator from a Honda CX500 can be kept below 200 degrees if you have a big enough oil cooler. Both systems do the same thing. The only difference is the cooling medium, oil versus anti-freeze/water mix.

The oil's primary function is not cooling, though, and it isn't as good at cooling as water/anti-freeze, but it does work.

In all this writing I may have missed the question, but what about a fan shroud? I know that will improve cooling.
Another interesting item... I had an engine once that would eat water pump fins. The engine was built with casting sand still inside the block. Every two or three years the temp would begin to rise and I would have to flush and replace the water pump. It was not a 350 but a F#@% 360.

starkweatherr,

Very well put. That is the exact thought I have been trying to put across the entire time...radiator cooling capacity is the key to the problem. It must always be higher than the expected worst case scenario of the engine it was designed to go in front of.


Stuart

Big Chevy 3600, you need to read a little about Cold War Soviet tank engines. Big Diesels, and a nice design, but there was no apparent effort made to clean out the casting sand, at least on export models. One engine donated by the Israelis to the US for testing had 17 pounds of casting sand in the lubrication system, but it worked fine all the way to the battle field.

Your point about radiator shrouds is well taken. Most race cars have aluminum ducting to make sure that the optimal amount of air goes through the radiator, and not around it. If you look at the engine compartment of a 50's or 60's car or truck, I think you will see that there wasn't much consideration made for ducting.

How about something really simple, though? Someone mentioned heat building up in the engine compartment due to a change from cast iron manifolds to tubular headers. Hmmm. How about putting a few washers between your hood hinge mounting bolts and the hood? In a wind tunnel, or an auto show, you might be able to tell the difference, but a 1/8 inch gap between the back of a 30 inch wide hood and the windshield gives you a little less than 4 square inches for air to flow through, carrying heat with it. Also blows rain off your windshield.

Stuart, I agree wholeheartedly. Frankly, I can't imagine designing a cooling system for perfect conditions, ONLY. Especially for vehicles that may be driving 10s of thousands of miles without checking the fluid level in the radiator.

Once again, it is quite possible to run a modern engine with no cooling system whatsoever, and Top Fuel Dragster drivers do it every day, but they don't spend much time in stop and go traffic.

BTW, several years ago I read something that may, or may not, be true about running mid 60s engines with no fluids at all. When you think about it, there are a surprising number of cars/trucks that come off the assembly line that have minor errors on them, like RAM 3500 on one side and RAM 1500 on the other. These are usually gurred by a bulldozer and re-cycled, but you can see where a vehicle could come from for the 'no fluids' (except gasoline) test.

Supposedly, GM did the best with a run of 17 feet.

I am building a 36 chev sedan hot rod and the 350 was just rebuilt, the rad was recored and every thing else is new. I have been running it lately and at 210, I worry and turn the engine off. I have used the Wet Water and the temperature got up to 210 today. At 210 the engine is some tinmes stalling. I am thinking that could be from the heat and plan to look into cooling the engine compartment. I am use a 16 lb rad cap.
I just do not want to distroy the engine (at least most of the time!)