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Potent Rodent

New built engine, EFI, 4L80 transmission, t-case, brakes, hydroboost, tires/wheels and more!
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I would guess that the water pump is a better one than the one that gave me problems then. The factory lower hose does about the same thing. And I hope that you are correct about it having an air pocket. I did see guy have one in a fat block with a horrible air lock. He fought it for a couple of days, and then got mad and revved it up to around 4K.... it suddenly sucked in more coolant, then was cured. Maybe you can point the nose uphill?

I had twin electric fans on my '70 for a while, which can only fit the 18" tall radiator. It was fine except that the fans cycled more than I wanted to when the A/C was on. Going back to a mechanical one gave more consistent air flow for the condenser.
 
Ordered the Windstar fan the other day. Should be here next week. Drove it around today but not too far. Slowly creeps up in temp even while driving 45mph which is telling me it might be more than the fans unless the dual 12" holes is not allowing enough air to get through. I drove it 3 miles to the tire shop where it was up to 200 degrees which is ok. Then let it sit for about an hour or two to cool off while they replaced my cracked valve stems. Drive it back home, few stop lights, 45mph most of the way until I got in the neighborhood. By the time I got home and shut it off, it was at 208 degrees. My thermostat is a 180. Many of of the Dart block owners suggest drilling a few holes in the thermostat which helps with Dart block since it has no steam holes like the GM 400 block. I still need to call my engine shop and see what he suggests.

http://www.montecarloss.com/community/ubbthreads.php?ubb=showflat&topic=76902
 
Where is your temp sensor for your gauge mounted?
 
Top of intake manifold next to thermostat. Not in the head.
 
my buddys blazer i built we did sender in intake next to t-stat and its rock solid once up to temp .

he has a built 400 sbc around 10:1 comp and 4 core copper brass rad . i stuck a ford focus 2012 and up fan i had just to try it and unless he is in traffic he dont even hear the fan kick . 15mph and up she stays steady on temp . just parts store new or reman cast iron water pump is all .
 
Some thermostats have small bleeder holes already in them. If they don't, I drill 2 small holes in the plate area of it to help calm down the temperature swings and also eliminate the spike of temperature, then sudden drop when the thermostat opens.

I used to get Robert Shaw thermostats which were awesome! But they got bought out and aren't as good as they used to be.

If you could pull the fans and shroud out , then drive it at a steady speed above 40 mph, I would think that you could determine if airflow is the main problem.

A flow test on the water pump would be great, if there was an easy way to do that. But reality steps in...
 
One way to help determine if its airflow or water flow is to measure the radiator temp and compare it to the engine coolant temp, maybe with an infrared gun or contact probe.

If the radiator temp is significantly lower (particularly on the side going back into the engine) that points to water flow.

If the coolant temp in the engine is nearly the same and the radiator is just as hot then its likely airflow.
 
6872xtc said:
Some thermostats have small bleeder holes already in them. If they don't, I drill 2 small holes in the plate area of it to help calm down the temperature swings and also eliminate the spike of temperature, then sudden drop when the thermostat opens.

I used to get Robert Shaw thermostats which were awesome! But they got bought out and aren't as good as they used to be.

If you could pull the fans and shroud out , then drive it at a steady speed above 40 mph, I would think that you could determine if airflow is the main problem.

A flow test on the water pump would be great, if there was an easy way to do that. But reality steps in...
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Good advice! I will be drilling a new 180 thermostat out with two 1/8 holes. Then i'm going drain all coolant and add distilled water with some cooling additive like water wetter which has been proven to help. I realize I will have to drain it out come winter. It that doesn't work then I'll be look at the water pump and fans. Either way I have the new Windstar fan coming today. The only problem is time. I have less than 5 days to pack up my house, garage and large shed. We move Saturday so I won't be able to address the fan till a couple weeks from now. I think the K5 will be able make the journey at night to the new house which is 9 miles away.

folkenheath said:
One way to help determine if its airflow or water flow is to measure the radiator temp and compare it to the engine coolant temp, maybe with an infrared gun or contact probe.

If the radiator temp is significantly lower (particularly on the side going back into the engine) that points to water flow.

If the coolant temp in the engine is nearly the same and the radiator is just as hot then its likely airflow.
Click to expand...
Good idea. I think I may invest in a laser infrared temp gun. Been wanting one for awhile now.

The other thing I was looking at last night is hose diameter size. Long story but I was forced to go to AN fittings at the lower hose. I used -20AN which is 1.25". And -20AN on the top hose. Most people get away with -16 but I was hoping the -20 1.25" lower hose was not restricting the flow. Most aftermarket radiators that use AN fittings have this size as selection for lower. Maybe a -24 would have been better. When you look at the size of the thermostat outlet, I don't think this the issue but something I have to take into consideration.

I think the thermostat drill mod, and Winstar fan will fix the problem but these are all great points to bring up when having cooling issues.
 
I can't recall what the exact CFM of my fans were but I want to say I had two 12" really good fans on my buggy with the marginal radiator and it barely stayed cool, thinking I had 5,000CFM out of them.

Sitting on the sidelines and reading I think you have air flow issues and perhaps a bit of airlock. We're running 1.5" .120 wall tubing for the water lines to the rear radiator in my buggy with no special mods to the water pump. bleeding air sucks but the holes in the thermostat help a bunch.
 
If that's the exact rad/shroud you have there's probably some spal fans that may mount up as well.
 
Well I already bought the windstar fan but havent installed it yet. So now it only got up to 187 by changing out the thermostat with a high flow with holes drilled out and going to distilled water with a cooling additive. The weird thing is I ran some readings with an inferred temp gun and the sensor seems off.

192 Temp after engine was off for a minute (sensor)
160 below thermostat (laser)
145 above thermostat (laser)
140 Top radiator inlet (laser)
112 bottom radiator outlet (laser)

I wonder if my temp sensor is off 30 degrees?

Current shroud with 12" fans
20190807_151247.jpg
 
I had to replace the CTS that came in my EFI. Granted it's the much maligned Sniper EFI, but maybe a common problem across the board.
 
I'll have to measure the resistance on the sensor and see if its within specs. Tried it again when it was still warm after 1 hour and it was only 13 off. I can always replace it just to see if that helps.
 
Shawn said:
I'll have to measure the resistance on the sensor and see if its within specs. Tried it again when it was still warm after 1 hour and it was only 13 off. I can always replace it just to see if that helps.
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Have a mechanical gage too or just the Efi?
My PF4 is dead nuts on the mechanical gage
 
Keep in mind that there are some temp guns that read differently on different surface colors. I personally haven't used one that read properly on an aluminum surface, and cast vs polished can change it a little with the 2 guns that I have used. So I give it some leeway when comparing to a probe thermometer. (Sensor)
But my experience may be different from other guns.
 
Bent77 said:
Have a mechanical gage too or just the Efi?
My PF4 is dead nuts on the mechanical gage
Click to expand...
I dont and I wish I did. My stock gauge is WAY off since I used the wrong sensor. It's the smaller diameter sensor due to my AFR heads. I thought I got the correct sensor but I guess not.

6872xtc said:
Keep in mind that there are some temp guns that read differently on different surface colors. I personally haven't used one that read properly on an aluminum surface, and cast vs polished can change it a little with the 2 guns that I have used. So I give it some leeway when comparing to a probe thermometer. (Sensor)
But my experience may be different from other guns.
Click to expand...
Good to know. I'm not sure how accurate this laser is and I am measuring bare alum. I really need an aftermarket gauge to verify.
 
Shawn said:
I dont and I wish I did. My stock gauge is WAY off since I used the wrong sensor. It's the smaller diameter sensor due to my AFR heads. I thought I got the correct sensor but I guess not.


Good to know. I'm not sure how accurate this laser is and I am measuring bare alum. I really need an aftermarket gauge to verify.
Click to expand...
When I was having issues, the mechanical gauge kit from summit is like $40. Still mounted under the hood after my last diagnostic session.
 
Shawn said:
I dont and I wish I did. My stock gauge is WAY off since I used the wrong sensor. It's the smaller diameter sensor due to my AFR heads. I thought I got the correct sensor but I guess not.


Good to know. I'm not sure how accurate this laser is and I am measuring bare alum. I really need an aftermarket gauge to verify.
Click to expand...
Usually the temp guns are accurate on a flat black surface. Put a few dots of paint around in the areas you want to shoot and see what the temps are.
 
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