Technical SBC 350 - How hot is too hot?

Yes I set the timing when I put the new MSD Streetfire. Initial is set at 14 deg and total is somewhere around 34. I am running vacuum of manifold port on the carb.

 

Thank you. My initial question was how hot is too hot. It runs at 200 mostly at 25 mph speeds around town. At a traffic light I've seen it go up as high as 220 deg. Is that getting too close for comfort?

I am going to dilute the coolant by draining the radiator and putting all water. I'll check to see if there is air in the system and I will put a 180 stat. A shroud will help and I'll put that on the list but will try the other things first.

 

I do not like to see 220 on a SBC. 190 to 200 is fine IMO. My blown 406 in the coupe runs 195 in traffic on a 95degree day, no problems. I have seen big blocks get to 230 240, and no harm done.

 

1. Run 80/20 water/coolant
2. Put a 180 thermostat in.
3. Put a damn shroud on it.

 

Thanks. Would draining the radiator fully and leaving what's in the block alone then filling with water probably get me 80/20?

Will do on the 180 thermostat.

I will look for a universal shroud after taking some measurements. One thing I wonder is whether the 53/54 stock radiator is enough for a SBC 350

 

Engine efficiency

 

If not said yet,,, get a shroud

 

220 is not too hot for in the summer time, but it's a bit warm for this time of year.

Did you make sure the cooling system is completely full after you worked on it, then drove it around? if it had some air trapped and you didn't check after getting it warm, it might be a bit low, that would make it run a bit hot.

195 thermostats and 50-50 antifreeze mix have been used in all new cars for the past 45 years, there is nothing wrong with them.

 

From every thing I have seen you write over the years this is the first time I saw any thing that I thought was total BS and if you read it again you know most of it is.

First the antifreeze mix keeps the engine's coolant from freezing when it has been sitting for a couple of months in the driveway or if it has been running non stop with an air chill well below freezing hitting the radiator but "retaining heat to keep it from freezing?" has nothing to do with the way it works.
Yes the mix will let the coolant get hotter before the engine pukes coolant all over the driveway when you stop but it doesn't arbitrarily cause any engine to run hotter it just lets and engine run hotter without boiling over.

True though since he lives in San Diego he probably can get by with a lower percentage mix that will help prevent rust in the water jackets and lube the water pump as long as he doesn't decide to load up his favorite hottie and head to the mountains to a ski lodge for the weekend in the middle of winter because that will cause the BMW brigade to fall into uncontrollable laughter about the guy with the old car that's radiator froze on the way up do to no antifreeze or his waking up to a cracked block because it froze overnight.
As far as the 220 in traffic thing I'd say that is normal for 90% of the 350 engines on the road in stock cars or trucks. If the temp drops back down to just above the setting of the thermostat and stays there on open flat roads at road speed no worries.
If every time the car gets in traffic for a while and it starts puking coolant he has a cooling problem though. No puking no problem just like your drunk buddy


0

 

Thanks, so 20/80 is better and will help with corrosion?

 

Thanks, basically I can pull the radiator cap off and look at the level? The last time I had checked after doing that coolant work the fluid was right up to the cap after letting it cool down completely.

 

Thanks, there is no coolant puking at all. When I get back on the road the temp drops back down to 200. Before I changed the coolant I remember sometimes it would drop to 190 or even 180 at times, especially on the highway. I will check for air trapped in the system to be sure.

I will never take that car to the mountains in the winter, it will only stay in the immediate San Diego region for the time I own it. I thought 50/50 would be fine and in case this car ends up in someone else's hands in the next couple years they won't have an accident by going to colder climate with it.

 

Ok
actually its not nonsense nor BS but since you called it-twice,,,

Why don't you then explain the process of "freezing" ,,, I left the dry technical aspects aspects out. But the laws of physics, energy transfer & thermal equilibrium still apply. You'll need those to probe your call of BS.

Its pretty well known fact that the cooling efficiency (ability to shed heat) of Anti freeze mixture is much less than that of water. You might not know that but its true.

 

I am no expert by any means, but I did go through a lot of trouble to keep my 50 cad running cool.

The most crucial things I did - popped out 6 freeze plugs on the side of the block above the oil pan. Used a coat hanger to dislodge all the greasy gunk in there and jammed a garden hose in each hole to really flush it out. I then ran a degreaser in it over night and flushed it again really really well.

Then I had my radiator rodded out. It was plugged up with some shit the previous owner added to it.

160 degree thermostat with a 1/8" hole I drilled into it.

New water pump and hoses

Set timing

50-50 mix.

My own PERSONAL opinion - playing with the coolant mix ratio is BS. In my mind, thats not solving anything.

Run whatever thermo the factory reccomends for that setup.

Just my 2 cents.

 

Sometimes when you are looking at a problem you are looking too close and can get side tracked. It has happened to me over the years.

This is the first thing that you need to do^^^^^^^^^^^^^^^^^^^^

Can you post a pic of the rad please. Are you sure it is a stock 53/54 rad? What is the condition of the rad? If it is a stocker it might need a good boil out. (cleaning)

Jay

 

Shroud Shroud Shroud Shroud

 

The level wants to be as high as it can. That means that if there is no coolant recovery tank, it may not be all the way to the top, since it expands and pukes out a little bit when it gets to operating temperature. If there is a recover tank, then it should be right at the very top of the radiator. There are some exceptions for car that have some part of the cooling system higher than the radiator cap...usually this does not apply to something like a 53 chevy.

 

I bought one of those from speedway. Didn't do shit. If anybody wants it it's yours for the cost of shipping.
Pat

 

Here's the name of the tech thread for the fan shroud.
TECH: Custom fit fan shroud.
When I got done making mine I painted it semigloss black and it looks like a factory shroud.

 

when you switch thermostat, get Mr Gasket High Performance Thermostats 180 - # 4364. Will give you warm up at first start up, then provides a higher flow of coolant than standard styles - known as "Robert-Shaw Wide Mouth" too. what pressure radiator cap are you running?, can make a noticeable difference in temp. those shiny partial fan shrouds only protect fingers from the fan. for cooling must have a full shroud - there are universal made plastic & aluminum shrouds available on summitracing.com.

 

Something i don't think anyone asked is how and where you are getting your temp readings.
If your probe is in the head it can read higher then in the thermostat housing, and a temp gauge can also be off by several degrees.
A system with no overflow can, will burp out enough coolant to make room for expansion. That will leave the coolant level down probably about 3 inches give or take from the top of the radiator.
Once that happens it should no longer burp out any. If your not boiling out coolant every time you drive it, then your temps are most likely fine.

 

Lot's of conflicting and arbitrary/anecdotal advice here, if I were you I would investigate around a little bit more on other websites/forums, maybe some that are coolant specific. It is true that water has better heat transfer properties than antifreeze, but it is also true that antifreeze has a higher boiling point than water (ethylene glycol boils at 387 F), and most coolant and cooling system experts agree that a 50/50 mix gives about the best performance for most situations. If you want to adjust the ratio to something more along the lines of 60/40 or 70/30, use a hydrometer to measure the specific gravity. Again, do some more research elsewhere, this information is out there.

The original question was, how hot is too hot. Unfortunately there is no 1 correct answer to that, it depends on the situation. Ultimately the "too hot" point is the point where the coolant boils and turns to steam, steam doesn't transfer heat from your engine very well, at that point it's only a short time until very bad things happen. If you're lucky maybe just a blown head gasket, if you're not so lucky, it may be cracked heads and/or seized pistons. As a rule of thumb, as long as the radiator has not boiled over it's not too hot. But rules of thumb can fail you, and old head gaskets can fail and heads can crack before that if they are marginal to begin with; and pistons can seize if they expand too much due to the heat, and that depends on whether they are forged or cast and how much clearance they have.

Increasing the pressure in the system raises the boiling point of the coolant mixture, using a 15lb pressure cap and 50/50 coolant mix the boiling point at sea level is about 260 degrees.

IMHO I don't think you have a real problem, 220 degrees at idle is fine with a 15lb cap. I would make sure that hoses are in good shape, and the clamps are tight, they will be under a lot of pressure and heat. That includes heater hoses if you have any. If it really bothers you that do some of the things mentioned here, i.e. install a 180 degree thermostat, and fit a shroud, make sure the belt(s) are tight and the radiator is unobstructed and the fins aren't all bent over. It's always possible the radiator is plugged with corrosion internally, and you can have that cleaned at a radiator shop (are there any of those left in San Diego?). Personally, I'd stick with a 50/50 water/coolant mix, but that's just me. I also wouldn't worry too much about it if it was off a little in either direction, but if I had to choose I would go with a ratio of more water than anti-freeze.

And if I were you I'd double check on this advise too, google is your friend.

 

Thanks the temp probe is in the head. I had read that could give the highest reading over the probes that are on the intake manifold.

It has an overflow can. I haven't seen coolant burp out onto the floor at any time.

 

Thanks that is a lot of good advice! I might as well buy a new radiator cap. I'm not sure what mine has but I'll get a 15lb one.

 

If your radiator is the original one. You might want to get a cap suited for the radiator. Which might be 7 LBS. if I'm not mistaken. Check.

 

Here are some photos I took earlier in the year. The first one is when I had to take a head out due to a valve issue. I reused the same coolant. The second one is with the head replaced and the coolant put back in. The coolant I drained was quite green. I had topped off the overflow tank with a coolant that had an orange color but was fine for GM cars. That is why it has that color.

The motor ran at the same temps after I did the work. I didn't notice a difference until after changing to 50/50 mix (this mix was all green by the way).

The radiator is a stock 53/54 but I don't know when it was serviced, or how old it is. I will ask the previous owner.

It's a hassle for me to go in the 1 car garage and open it and take photos right now (roommates car is blocking etc). Here are some photos from earlier in the year. These were before I changed the coolant.

The hardest thing is building a shroud. I don't really have a place to do this, I have really limited space and tools right now. The previous owner ran this without a shroud. The only thing that comes to mind is a universal one that covers the entire radiator but I don't know what solutions exist for one like mine. I looked on Jegs and Speedway and nothing obvious.

 

Thanks what I will do is look at what's on there now next time I can open the garage up. Since I don't know how old it is I will plan to replace it.

 

that radiator should not have a cap higher than 7 psi. Higher pressure will blow the radiator apart.

I would just drive the car and try not to worry about it. If the temp never gets over 225 or 230, it's not likely to boil over. If you want to save up your money for a new radiator, that would be nice, and if you want to add a shroud, that would be nice too. but you can drive it as it is...just don't let it get to the point where it boils over too often!

 

I live in Alaska... So we run a 60/40 coolant over water mix. Obviously not ideal for the og posters issue...
However, we flush plenty of first winters L48ers radiators that ran straight water or 90/10 and so on. Often taking 3, 4 or even five flushes with the flush gun (not a simple exchanger, but pressurized flush gun) to get all the rust out. That rust not only is making cylinder walls thinner in the block, but is clogging the radiator/heater core and so on. Decreasing the heat transfer abilities of the coolant, but the radiator efficiency too.

The supercharged corvettes, turbocharge subarus and so on run a 50/50 mix.

It's not the coolants fault. Something else In the cooling system hasn't been designed right.

 

Wait! If you're still running the 53 chevy radiator, keep pressure down to whatever a 53 chevy ran...you can bulge or rupture the radiator tanks by using a high pressure cap. I'd also recommend using a coolant recovery tank to keep any air out of the cooling system and to maintain proper coolant level.
If you do this, use a recovery type cap....all these small things help to keep the temp down.
also....close off any air leaks on either the side of the radiator. This will direct cooling air through the radiator - not around it.