Technical SBC 350 - How hot is too hot?

Hi All,

I have a SBC 350 motor in a 53 Chevy. The fan is a mechanical one on the pulley. I know I should eventually look into an electric fan, a shroud, etc.

Prior to moving to an apartment with a tiny garage, I had a 2 car garage and I did a lot of work to the car. I drained the coolant and put 50 percent Prestone concentrate and 50 percent water. I'm not sure if that made it worse but my motor is running rather hot.

The ambient temps were 74 degrees today in San Diego. At stop and go roads, the motor runs around 200 degrees, and at a stop light it gets close to 210 and even close to 220 at times. Going a little faster on the road it drops a little below 200.

Prior to changing the coolant it might have run 5 to 10 deg cooler in each of those scenarios. The previous owner said it might have a 195 deg thermostat.

What should I do in the meantime (putting an electric fan and shroud is a project I will have to wait a few months to do)? He said there is something I can add to the coolant that works like a miracle to provide coolant but I forget the name of it. I wonder if he had put that in the coolant before.

 

Yes...it's called a 160 degree thermostat, but I noticed you are still having brake problems and if your brakes are dragging then that is why not only your brakes are getting hot but your engine as well!

 

Thanks.....
Interesting. However I didn't feel the engine loaded up at all and I didn't feel the brakes dragging at all. No weird issues with the brakes hanging up on their own.

I noticed the engine running hotter when I changed the coolant. 5-10 deg hotter. Do I need a different thermostat?

 

try a 180 thermostat. straight water will cool better than a mix.

 

Why would you need a 195 in California, do you need to pass some emissions tests with that old of a vehicle? Or do you require good heat for those COLD winters you have there ? That Water Wetter that you can't remember the name of is just another half assed fix that you will be adding to your car.

 

A 50/50 mix of anti freeze will protect you to -58 F. It does that by holding its heat. That's great in the arctic, not so great in the warm. A 50/50 mix will raise the boiling point but since it holds heat a 50/50 mix will cost you 30% cooling efficiency or its ability to shed heat. That's like blocking 30% of your radiator.

It may have been "water wetter" ?

 

220- hmmm
My honeys car doesn't even get the fan on till 226f

 

I have no idea why the previous owner would have put a 195 thermostat in it. Yep I remember him saying Water Wetter.

So what should I do, put a 180 thermostat and drain the coolant half way and maybe put water in the rest?

 

Thanks, the previous owner told me he remembers someone telling him you don't have to worry until the motor temps get to 220.. I don't know.

 

In either case it seems like I should drain the coolant yet again and fill with water only or should I drain it half way and fill the rest with water or maybe 2/3?

I thought some of the anti freeze was to help with controlling rust as well?

 

just drain it at the radiator, the block will still have some antifreeze in it.
temp is not the problem, boiling is. steam will do damage, that is why there is a pressure cap.
i have a friend that runs his race car at 250 degrees.

 

The car will run way better at 195 than it will at 160.

An electric fan isn't an improvement, its a Fix for spacing issues. Get a shroud for your mechanical fan.

Run a 20/80 mix if you think temps will get below freezing. that will give you enough corrosion resistance and pump lubricants.

Or just the water wetter.

 

Thanks, the car isn't leaving San Diego and I don't drive it on cold mornings. Given that, should I drain at the radiator and just fill the rest with water as tb33anda3rd suggested?

I will have to research a shroud that would fit the 53' Chevy radiator and the fan on the SBC 350. That will be a project but a thermostat and draining the radiator and filling the rest with water is something I can do for now.

What should I do about that 195 thermostat try 180 as tb33anda3rd said?

 

Get this tattooed on you someplace.

"When a new problem appears,
Look at the last thing you did"

So you drained the system, filled it with 50/50 mix and now ,,,(did you do anything else ? Tune up? Water pump?)

(Heavenly choir) uuhaaaaa
It's running too hot.

Did you happen to test the old stuff with a hydrometer? Do you have any idea what it was?

 

Whole bunch of possibilitys, Is the radiator big enough for a 350? Is the engine stock? Is the timing correct (advance/retard). Is the fan large enough, does it have a good "pitch" to the blade? How well centered is the fan on the radiator? How close to the radiator is the fan? 1/2 in. to 1in. is a good range. Late model 350's (center valve cover holes) usually run 210 degrees, but that's factory engineered car/truck set ups. A 160 or 180 degree thermostat should help. A fan shroud could well be a big help. There's no logical reason for the engine to run hotter just from changing coolant. Any chance you have air in the system from when you changed the antifreeze? Because the temperature comes down when your moving at speed, it's usually a sign that your not pulling enough air through the radiator with the fan because when your moving along air is being passed through the radiator by your speed. Does the radiator spit out coolant? Does it have a coolant recovery system? Most engine swap set ups respond well to a recovery system. BILL RINALDI

 

Yea I know I have tried to trace what changes since last time. The car has always ran hot since the day I got it. It seems to run 5-10 deg hotter since changing the coolant.

I didn't change the water pump, nor the thermostat or anything else I can think of that would have affected the temps. I did change the timing but that was before changing the coolant and I didn't notice any significant temp changes in the motor after that.

 

Just swap out for the 180 and leave the mix you have.

 

Thanks for all this great advice. Basically the previous owner ran the setup he had (fan, radiator, pitch blade, etc) for a while and I had no problems with it for now. I noticed it running hotter after changing the coolant. I have the timing set to 14 deg base and somewhere around 34 total.

I don't think I have any air in the system. I filled to the top of the radiator and never really saw the level drop even after letting the motor warm up. Then after running it around town I had let it cool off and I checked the fluid at the radiator and it was to the top. I know with some cars you have to let the thermostat open up and watch the
level drop and keep filling. I didn't experience that with mine.

It started up first shot today (it has been 3 weeks since I last tried) without even taking more than a second. When I put gas (after driving it for 30 minutes) it took me 5 or so seconds of cranking for it to start. The motor temp was around 220 then.

Hmmm...

 

there's an old tech thread on here somewhere that shows ya how yo make your own shroud by making a plywood form and using fiberglass. I made one over the summer for my 51 fleetline with a 350 in it. came out great and seems to have helped a lot. I'll know better when it gets hot here again next summer.

 

Thank you for the lead. I will search and see if I can find it!

 

Is there a 1/8" hole drilled in the top of your thermostat to bleed off air when you are filling the system? I like to take the temp sensor out of the intake when filling, until coolant comes up to that point anyway. Sounds like air bubble.

 

For about $30.00 you can buy a universal chrome shroud that will look way better and be cheaper than plywood & fiberglass.

 

Awesome is this on Jegs or Speedwaymotors?

 

Thanks, I don't know if there is. I didn't put the thermostat in. I had filled it with the new coolant to the top of the radiator. Then I let the engine run until the upper hose felt hot and then I knew the thermostat had opened up. I noticed I didn't need to keep adding any more coolant. This surprised me. However next time the engine was completely cool the level was right up to the radiator cap so the level didn't drop.

 

I've seen them a swap meets, made in Taiwan or China of course but I'm sure they can be found elsewhere as well. Got any speed shops in your area? They do come in different sizes though and depths 3 or 5 inch I believe so make sure you see how much room you have and measure the diameter of your fan as well.

 

just google "universal chrome shroud"

 

check to see if it even has a thermostat.

 

True! I will buy a 180 thermostat and plan to put it in regardless.

 

Has anyone thought about what the timing might be set at? Make sure you check the timing before you spend a penny on it.

 

Put in the 180 stat, dilute your coolant a little, and see where temp is. 200 degrees on a SBC is not that hot at all. If you have a issue in traffic, you will need to look into a shroud, or better fan.