Technical SBC 283 Thermostat-Cooling

Hello,
I’m looking for some reassurance or guidance after replacing a thermostat in a SBC 283.

preciously, there was no thermostat installed. Only a circular piece of sheet metal with about a dime sized hole was in the thermostat housing. I had no issues of overheating and my temperature readings were around 180-210*. I changed this to a 180* thermostat (Napa) as the weather here has started to stay in the upper 90’s. Since doing so, I’m noticing my temperature gauge is reading 210+, and 230-250 while driving between 40-55 MPH. I have only done short trips of approximately 10 minutes just to be safe. As I begin to slow down, come to a stop, or even park, the temperature gauge drops back down to around the 210-220*.
The gauge is from Autometer and brand new.

I’ve used a laser thermometer at the housing right next to the temp. Sensor and was getting readings of 190-200*. The upper coolant hose was around 130*, and manifold temp was between 170-195 approx. depending on location. 16” electric fan is installed and operational via switch.

no other issues with performance, and no coolant blowing out of the reservoir. Does anyone have an idea of what could be going on or if it’s worth checking in to?
My only worry is being in traffic while it’s 100+ out and overheating.
I have attached a few pictures of my temp. Sensor location, pulley setup, etc. if any additional pictures or info. Can help out here, please let me know. Thanks!!

 

I don't know why the temp gauge is reading like that.

But you don't have nearly enough wrap around the water pump pulley, the fan belt isn't getting much of a grip on it.

 

Good catch Squirrel, could be that the belt is slipping on the pump pulley. Not much else to tell from those photos. Besides the potential of a slipping belt, there is also the potential of air in the system, not getting all the air purged after installing the thermostat. Rules of thumb on cooling system issues is, if it gets hot when sitting still or at slow speeds, not enough air flow. If it gets hot at highway speed, not enough coolant flow, or insufficient system capacity. If the engine runs hotter with a thermostat in it than it did with the washer, I'd say put the washer back in. It's possible the thermostat is not allowing as much coolant flow as the spacer did.

 

What squirrel said!

 

That belt is definitely something to check out
I had a SBF that ran cooler with a warmer stat.
Have no clue why.

 

thanks for the insight. What would my options be to correct this?

 

Thanks for the reply. I’ll look into getting some possible air out of the system and possibly throw the washer back in.
oddly enough, I noticed the polarity of the electric fan was backwards and was causing the fan to push air from the engine side instead of pulling it through the front of the radiator. I’m sure correcting that will help, but may not solve the issue totally.

 

....and check your L/H front header bolt

 

Haha I actually noticed that while trying to figure out a possible solution here. Good looking out though!

 

If the Only thing you changed was from a Restricter to thermostat .
More likely Air in System,
But also some times you need to play with Stat Temps to your liking.

Removing air when so much higher then thermostat.
Drain Rad down fill slow ,
Or jack front up , fill slow .
Or remove Thermostat fill block /intake slow until intake full then install thermostat , fill radiator slow.
Belt to pulley rap / contact questionable, You are not running a fan
So might Not require that much rap.
With Fan definitely would need more alternator swinging over Vavle cover by a few more inches.

 

Thanks for the advice. I’m going to try and get some air out the system and see what happens. Looking at similar pulley setups online, it looks like this one is commonly used for vehicles w/ an AC compressor on the passenger side. The belt from that would wrap on the adjacent side of the water pump pulley using the second grove.
Since I don’t have ac, I’m looking for the easiest solution. I could mount the alternator lower. I’ve also thought If I could fit a new V belt on the pump/crank pulley using the second grove. Problem is, I’m not sure I could get the belt installed since there’s no tensioner for those two pulleys. Water pump pulley would need to come off I think. Again, looking for the easiest solution to the possible lack of contact between the belt/water pump.

 

Add another belt. Mine have two belts, it's quite stiff to add it, but doable.

 

The easiest solution for the belt issue would be to add a second belt around the water pump pulley.

 

there was no thermostat installed. Only a circular piece of sheet metal with about a dime sized hole was in the thermostat housing. I had no issues of overheating and my temperature readings were around 180-210*.

If you had no over heating issue before with just a restrictor then its not the belt not sure why one would think that if it provided enough water circulation before . a slipping belt is pretty easy to hear and notice as well

Its more likely the new thermostat is off a bit in its calibration .
if its a 100 degrees out when your driving the stat is likely open all the time any way once warmed up .

 

Put the washer back

 

The reducer washer use to be a standard circle track item used to slow down the coolant to the radiator so the coolant would spend more time in the radiator to cool. In your case when you put a thermostat in I think you have found your issue with the fan pushing hot air through the radiator. So fix the fan rotation. Fixing the fan belt fit would be a good extra measure. Having a thermostat is usually a good thing.

 

The washer/restrictor can't fail .

 

The simple answer is that your thermostat is probably opening a bit late and not full open until 210-ish.

 

By relocating your alternator to get the belt to grip the pulley as Squirrel mentions will help. I also noticed from one of your pictures that your fan isn't cooling a lot of your radiator. A shroud will certainly help as it will pull the air thru all of the radiator.

 

You might a max open thermostat, I run one. You do need the the 2nd belt from the pump to the crank. 90% of the circle track guys run them. With your tight fit only the fan would need to come off. It’s not really that hard. We also run restrictors. Speedway offers a few sizes. You might need the next biggest one….ALWAYS use distilled water for your coolant mixing.

 

I think some guys missed this. If it's running hotter at speed, it's not due to lack of air flow, right? It's due to either lack of coolant flow, or lack of cooling capacity.

 

Well, if your fan is running backwards trying to push air out the front while at vehicle speed air is trying to go the other way, it could be an air flow problem.

 

if the thermostat was all you touched, that’s the problem or the installation of.
The correct direction? Air burped out? bad t-stat?
Gauge reading off? Same gauge as when it had the washer?

dont seem like anything is running hot with those numbers.

 

like I said before, I don't know what's wrong with the gauge....

but something is

 

Does it SMELL hot? You said it's not running like it's overheating and it's not boiling over, so I think you may have a few compounding issues that all came to a head by restricting water flow with a thermostat when before it had a constant flow masking the issues.
I'd bet if you fix your fan belt situation, get your fan blowing in the right direction (and add a shroud for good measure), and drill a couple of 1/8" holes in the thermostat flange to let any trapped air out that can be giving you a false reading at the temp probe, your issue will be solved.

 

You have two belt pulleys, just derail a short belt onto the unused groove. You don’t have to move the alternator. Get the fan blowing in the right direction. I would get another gauge to verify the temperature, Autometer isn’t what they used to be (neither is SW). If the temperature readings are real, put the washer back in. I’ve had hit n miss luck with parts store thermostats for the last few years, most are 10 degrees off one way or the other.

 

I'd think so, but not after he mentioned his fan was running backwards. In that case it definitely could be no air flow as the fan is working against the air flow at speed. At slower speeds the reverse fan could probably overcome air naturally flowing into the engine bay, but not at higher speeds.

Once you get the fan pulling, instead of pushing, then remove the T stat and drill a 1/8" hole in the perimeter of the stat to keep it from getting an air lock when the coolant is filled. This wont affect how the stat operates, but will ensure no air is trapped, and make filling the system much easier.

 

The simple answer is something you have already mentioned. You need to move the alternator so that the belt wraps around the pulley better and can also apply more pressure against the pulley. You can do a lot of "let's try this and hope" solutions and you may injure your engine from running it too hot. No matter what else you might change, the tension and increased contact area need to be changed. As a belt slips, it also wears more and stretches while you are driving. It might even jump off the pulley. Squirrel made a good point when he noticed this.

 

Had a customer's hot rod that a few other people messed with trying to get it to stop overheating at speed and it turned out. The fucking fan was wired backwards.

 

Thanks for all the replies. It’s nice to have a place that offer some help. I’m still working out some of the kinks to this since purchasing.

Here’s my plan and I will update later today what I found.
I’m going to try and get more air out of the system, fix the fan direction, and install an additional belt around the water pump and crank pulley.

If that doesn’t change much the next step will be replacing the thermostat with a new one, or putting the restrictor back in, relocate the alternator, and fabricate a shroud.

note: gauges have all been upgraded previously and have not been messed with since adding the thermostat. Once I found the fan was pushing hot air, I believe this had something to do with it getting hotter while driving since it’s fighting incoming (cooler) air. I would have never known this if I didn’t check it while it was not running.

Thanks again!