[Pierre1967]

Hi,

My engine temperature fluctuates between 185 and 203 depending on different situations (normal driving, WOT, outside temperature, etc.) and averages 195 degrees 80% of the time with a 180 degree thermostat.

The engine probably develops around 425 hp and runs very well. I need your ideas on what I could do to make the temperature more stable and stay between 180-190. Here is my setup and pics:

- Firebird 67 400 c.i. 10:1, 700r4, 3.55, xe274 cam
- Electric fan (Mark VIII), alum. rad., DC variable speed controler, 40/60 mix + water wetter
- Timing is set at 30 (stock KRE heads)
- Alum. water pump

Thanks for your help !

[JLMounce]

You need the upper close-outs and if you don't have it, an AC car bottom pan. That will help direct as much cool air through the radiator as possible.

The First Gen F-Bodies have small core supports, it's a problem that isn't easily addressed.

Your engine behaves almost exactly like mine. I average 195 on a 180 degree stat and on the upper end it gets to around 204. It's important to note here that this is nowhere near overheating. In fact, with me KRE heads, I've found they like a bit more heat in them. If your temps don't continuously creep beyond that low 200 number, you're probably in a good place for the engine and any incremental gains you can make would likely take a good bit of effort.

I do suspect that the 180 degree stat I run (stand super stat) doesn't completely open until around 195 degrees or so, which is likely why the engine almost always runs at 195 degrees. If that's actually the case, dropping to a 170 degree stat may produce the desired result.

I have also though about bypassing the return fluid from the core support directly back to the water neck or intake cross-over. By doing that you are not re-introducing hot water back to the engine without it going to the radiator. That may also help here.

[Pierre1967]

Very interesting JLMounce, thank you for your feedback !

[grivera]

X2 regarding thermostat ratings and Jason's other tips - I check each one before install and some are off by 15 degrees of the rated number as to when they start to open.

Do you have the spring inside the lower radiator hose to keep it from collapsing at higher RPM? How about the proper impeller to divider plate clearance?

[MatthewKlein]

Originally Posted by Pierre1967

Hi,

My engine temperature fluctuates between 185 and 203 depending on different situations (normal driving, WOT, outside temperature, etc.) and averages 195 degrees 80% of the time with a 180 degree thermostat.

The engine probably develops around 425 hp and runs very well. I need your ideas on what I could do to make the temperature more stable and stay between 180-190. Here is my setup and pics:

- Firebird 67 400 c.i. 10:1, 700r4, 3.55, xe274 cam
- Electric fan (Mark VIII), alum. rad., DC variable speed controler, 40/60 mix + water wetter
- Timing is set at 30 (stock KRE heads)
- Alum. water pump

Thanks for your help !

Thermostat can be tested in a pot of water on the stove with a thermometer. I've had to do it on rare occasions where things didn't make sense.
https://www.napaonline.com/en/p/BK_7...&gclsrc=aw.ds&

Cooling an engine is the act of moving the heat from the engine to the radiator and into the air. If the water pump doesn't work efficiently it will run hotter. The radiator can only exchange so much heat - if its marginal on hot days it won't be enough. The fan has to move enough air.

Does the engine run hot at idle, around town, on the highway?

If its only at idle or slow speed I'd suspect the electric fan is not moving enough air. The faster you drive the more air is forced through the radiator.

[Pierre1967]

Grivera, no I don't have the spring inside the lower radiator hose. This is the first time I'm hearing about this ! ..

Yes for the proper impeller to divider plate clearance ..

Thanks !

[65madgoat]

Not an issue - just curious. What brand and size radiator are you running and how is that Mark VIII fan mounted to it?

[MNBob]

Something is not right. I have this same combo with no issues; although it is a stock engine. A Mark VIII fan on high will overcool the engine.

Is the fan a two speed? Make sure the controller is hooked up to the high fan wire.

Otherwise, the controller must not be allowing a high enough fan speed. You could bypass it and let the fan run on full and see what you get.

[RocktimusPryme]

I never have any luck with the traditional type of thermostats. I have however had luck with the high flow types. Several companies make them. They run 20-30 bucks but they are much better at opening when they say they open. If you are looking for stability I would start there. Its a relatively cheap swap, and if it doesn't work you can tell yourself that you have that part of the equation controlled so you can move on to other potential issues.

https://www.autozone.com/cooling-hea...E&gclsrc=aw.ds

Something else that made a big difference on mine was AC style pulleys with a smaller WP pulley. I don't feel like that gets talked about much when cooling issues come up, but that was the demon tweak for me.

[Pierre1967]

65madGoat ... Radiator is 28x19 overall (I don't know the brand), it's hold with two home-made brackets

MNBob ... it's a 2 speed, I'll check this to be sure .. tx

RocktimusPryme ... good advice, tx

[mchell]

Originally Posted by Pierre1967

Hi,

My engine temperature fluctuates between 185 and 203 depending on different situations (normal driving, WOT, outside temperature, etc.) and averages 195 degrees 80% of the time with a 180 degree thermostat.

The engine probably develops around 425 hp and runs very well. I need your ideas on what I could do to make the temperature more stable and stay between 180-190. Here is my setup and pics:

- Firebird 67 400 c.i. 10:1, 700r4, 3.55, xe274 cam
- Electric fan (Mark VIII), alum. rad., DC variable speed controler, 40/60 mix + water wetter
- Timing is set at 30 (stock KRE heads)
- Alum. water pump

Thanks for your help !

You don’t mention the ambient temp and humidity you were running in at the time….makes a BIG difference if experiencing this at 60-75 degrees or 80-100

My engine will run right at Tstat temp from around 70-80 degree ambient temps….above that things will start to change, the engine will exceed tstat temps at long lights but return to slightly higher than tstat temps while moving. Depends on traffic etc

[MNBob]

I went to Aldi today and the temp was in the low 80s. The readings on the Sniper handheld were in the 170 to 175 range. I think that Holley temperature sensor is high, thus car was running pretty close to the 160 thermostat temp.

What type of controller do you have? I have an AutoCool III PWM controller from the auto cool guy. It has an adjustment knob that will make the fan go faster or slower and I have it in the middle. The radiator is a new Cold Case.

[Pierre1967]

MNBob .. really cool controller !

Mine is from DCControl