maximum safe water temp

[chris71]

guys what is the maximum safe water temp for a typical sbc, just in case someone is sitting in traffic on a hot day and will know at what temp to simply pull over and shut her off before any damage takes place. 240? I think this may be good to know. also what damage would take place i.e. the heads would warp etc.....

[Andy4639]

That all depends on the model and make of vehicle. Early year motors I would say you are right on. If you have a good cap on the radator then 250 would be a good cut off temp.
If it's a late model then it may go well above that, my 07 Tahoe runs at 210-220 normally.

[68_chop_top]

Tough question since there are so many variables. 240 F is 10 pounds of pressure. Your radiator cap should handle that without boiling over. NASCAR will run 250 F all day. Your thermostat is typically 160 to 195. Engine should run at thermostat if everything is OK.

[chris71]

Originally Posted by Andy4639

That all depends on the model and make of vehicle. Early year motors I would say you are right on. If you have a good cap on the radator then 250 would be a good cut off temp.
If it's a late model then it may go well above that, my 07 Tahoe runs at 210-220 normally.

yeah i was talking about early motors like what we all have in our 67-72's. so now what would to the motor if it overheated, bad? anyone have any personal experiences?

[beautimus]

years ago i asked this question to several people. now understand i am talking about 35 years ago. the consensus i got back then was this.
at about 195 degrees the viscosity of the oil begins to go south, thats why most thermostats open at 180. so ideally you never want to see the oil temp hit 200 degrees, or you gonna need to change your oil because it will flow more like water and the film is too thin to support the crank and rods. and if it hits 220 or above, your in danger of warping a head or if its aluminum it could crack. Bear in mind this is advise from a time when oils and there additives were not nearly as good as todays. and the people i got this advise from were rednecks like me, not engineers.
But now a days it ain't uncommon to see 195 degree thermostats in a lot of cars. coolant and lubrication have come a long ways. so how hot is too hot?
my vote is, if the temp hits 200 degrees i am shutting mine down.
over kill maybe but i love my truck. my goal with any cooling system, is to keep it from hitting 195 even in the worst case senario. that way the truck is a lot less vulnerable to over heating when things aren't optinal.
that is my 2 cents worth,

[original_balzer]

OK Im going to interject here.

With modern coolants and oils AND modern alum. used in heads intakes and other engine parts, 260 degrees is dangerous. If your running alum parts that are OLD 60's-70's I would sugest lower temp more like 230.

BUUUUUUUTTTTT! DO NOT SHUT YOUR ENGINE OFF! pull over and put it in neutral and rev it up to about 1500rpm.
That way your fan should move enough air to cool your engine slowly AND it keeps the pump circulating the coolant. If you simply shut it off it wont cool off as fast and you run the risk of a steam pocket (no circulation) witch will warp heads and intakes fast.

[El Jay]

It's not uncommon for vehicles to run in the 200-220 range, or higher nowadays.
Shoot, they come from the factory with 195 thermostats, and the thermostats control the MINIMUM temperature, not the maximum.
50/50 antifreeze & water don't boil until about 265, with a 15# pressure cap.

The important things, at least to me, is, if your water temperature is higher than what you're comfortable with; pull over and open your hood. DO NOT SHUT OFF THE ENGINE. Run it at a "fast idle" until it cools a bit.
You have to keep the coolant circulating.

[Brock]

I think it depends not only on quality oil but the motor itself. Me and my nephew both run dirt track cars. Mine has an Olds 350 rocket (70's) and his has a sbc 350 (basically new). Mine runs hot every week (220-260)...2-weeks ago it went beyond pegged (265) and started coming up the other side...no damage (lose of power and I Idled around for a couple of laps). My nephews on the other hand got to 220 last week and he cooked it...bend valves, blew a head gasket, and who knows what else. I use Royal Purple synthetic oil, he used Castrol racing. Of course my motor did survive flipping 6-8 times last year so its pretty dang tough. Knock-on-wood

[Number98]

Also.......

When your starting to get high on the temp you don't really want to shut it down because the liquid stops circulating and can cause higher temps and more damage. If you can put her in neutral and run a higher idle this will get the fluid circulating and begin to cool down some....

Turning your heater on would help this also..... sounds crazy but...

[mr48chev]

Brock has pretty well nailed it.
The engine it's self along with the cooling system has a lot to do with it.
Yea sure if you are running a 216 or 235 with no pressure cap temps over 200 are probably going to cause problems and it will boil over when it gets over 212.
With a pressure cap and a 55 percent antifreeze coolant in the cooling system plus a good oil in the crank case temps up to around 230 shouldn't be an issue with modern engines.

My theory has always been that "if it doesn't puke water it isn't hot".

As mentioned above most modern engines have thermostats running from 195 to 205. Cads have had 205 thermostats for years. 455 Olds from 1968 through 1975 call for a 195 thermostat from the factory.

With a 180 stat the 48 usually runs around 183 going down the road and a bit higher if it is stuck in traffic.

The GMC with the 350 runs about the same unless I am pulling something but I don't get excited or wet on my shoes if it gets up around 220 as it runs 55% antifreeze and a 15 lb cap.

[caminokid]

What I have done for years on old motors is pull the thermostat in the warm weather months. It will run cooler. This way you dont have to worry about the damn thing locking up closed and causing problems. You know some of you are going to say its not good to run without one...but...I have done it long enough I am no longer worried about what the book says. From personal experience....I have had no problems.