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Block Flush, Need Advice

Do you have an IR heat gun? if not I suggest you get one. They are invaluable in diagnosing things. Check top hose and bottom outlet of rad to see how much of a temp drop you have. Then check front to back of block on both sides to see those temps. Back of motor will always be a little warmer. As others have said check pulley ratios , and your fan set up looks a little restrictive as far as air movement is concerned. you could in fact while driving around have a "solid" wall at rad opening, thus no air making it past the rad itself.
 
VitaminCRR said:
I had a 67 Firebird back in the day and it had an overheating issue that I (being a kid) could never figure out. It would slowly overheat and when I stopped it would puke coolant out the radiator cap. I tried everything I could think of to fix the problem but finally sold it like that. As it turns out it had a bad head gasket that was causing the problem. I couldn't drive it more than about 20 minutes before it got way too hot.
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Good point Vit C, I did run a coolant contamination test using the special tool and blue fluid to detect for any exhaust gasses escaping into the coolant but it passed with no problem. Also, using stock pulleys, nothing has changed there. It had the same problem with both the old and new radiators even thought the new Griffin radiator has about 30% more cooling capacity and is functioning as designed. It does take longer to overheat with the new radiator and electric fan. Sorry if I seem frustrated in my postings, I am. But I really do appreciate everyone who has offered continued suggestions. :)
 
It sounds like you're being very thorough with your diagnoses. I hope you find the issue and can share it with us.
 
I'm thinking at this point that the engine (which I have no history about) my have been bored out one too many times. Anyone have any experience with this problem? I've been told that could certainly be the cause of an engine running too hot. By the way, what exactly is 'too hot' for one of these engines. I remember my original 70 Road Runner 383, which I bought new, seemed to run around 190 - 200. It would occasionally start to creep up when running at high speed across the desert but I rerouted the windshield wiper washer hose to the front center of the radiator and would give it a squirt of water every so often and that kept it in check. (That technique also worked well for a power boost just before a street race). ;)
 
Ski 61701 said:
Do you have an IR heat gun? if not I suggest you get one. They are invaluable in diagnosing things. Check top hose and bottom outlet of rad to see how much of a temp drop you have. Then check front to back of block on both sides to see those temps. Back of motor will always be a little warmer. As others have said check pulley ratios , and your fan set up looks a little restrictive as far as air movement is concerned. you could in fact while driving around have a "solid" wall at rad opening, thus no air making it past the rad itself.
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Ski, I do have an IR heat gun I borrowed. What I need to know is what temp readings should I expect to see at the locations you mentioned? And what would be considered too high?
 
RRDon said:
OK, thermostat question; I've heard both pro and con that if you run without a thermostat the water won't have enough time to cool down and the engine will over heat. Likewise if your thermostat temp rating is too low, same problem. Now a mechanic friend of mind insists this is true. Can any of you experts verify this one way or the other? So what temp thermostat should a big block Mopar run?
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If your pulley ratio is 1:1 then I would either pull the thermostat and run without it or do what we used to do and put a stainless washer (with a large hole) in its place. Just enough to create a restriction. In the race motors we found the washer method made it run a little hotter, but we were running high RPM's except in the pits or on caution laps so we had a ton of coolant moving. In a street setup, a slight restriction might actually help a little.
 
Although not very likely, you could also have the w/p impeller slipping on the shaft. Have heard of it happening, then your velocity goes down.
 
oldbee said:
Although not very likely, you could also have the w/p impeller slipping on the shaft. Have heard of it happening, then your velocity goes down.
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Yup!!! Bought a lot of parts over the years that were junk right out of the box! Really tends to piss one off when the part was a two hour job to change and the jobber says, "Okay, here is a new one." Ahhh, that's what you gave me last time.
 
oldbee said:
Although not very likely, you could also have the w/p impeller slipping on the shaft. Have heard of it happening, then your velocity goes down.
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Yeah, the water pump is new and is working correctly. With the clear in-line filter I can see the water flowing rapidly through the system when the thermostat opens up. Like I say, all of the components of the cooling system have been checked and re-checked multiple times.
I did notice something a bit disconcerting though back when I was doing final flushing of the block using a garden hose; with the drain cock open all the way on the radiator and water continually running into the top of the radiator from the garden hose (at the same rate the water was coming out) the engine temp was creeping up and up. I did not run it long enough that way to see if it was going to over heat or not but it did go past 190 and was still climbing. Seems like that should not happen with an endless fresh supply of (relative) cool water coming in all the time. This was without a thermostat so fresh water was flowing through the block continuously. The ambient water from the garden was probably about 75 deg and the water coming out the bottom drain cock was hot and getting hotter the longer the engine ran. Seems to me this has to be something internal to the engine.
 
Pray tell, what your eyes(or mine) see as adequate water flow might not be.Also a 'new' part may not be any good, I don't necessarily trust anything new anymore!
 
"New and working correctly" Maybe, even at idle we could expect 10-17 GPM for flow. I am not sure what that flow rate looks like. The coolant can look like it is moving as it should but what is the reference. At cruising speed (60-90 GPM with a high flow pump) the flow is pretty impressive. Anyway, a bump in flow when the thermostat opens is only and indicator that the thermostat opened, not that the flow is correct. You also have to watch the whole CW and CCW pump rotation which can get messed up if you changed your belt/pulley setup at all. I am sure that you will figure this out, might even be as simple as the wrong PSI cap, IDK. Keep plugging away but I would pull back from the thin wall over bored idea. When turning 7-8 grand (or more) the motor puts out a ton of heat, and the cooling system can handle that so another 10 off the cylinder wall I would not expect to cause any cooling issue. Durability Yes, cooling No.
 
I asked before and got a curt reply but I'll ask again....

I know you put in a new radiator prior to flushing the block... I know you had overheating and debris from the block found it's way into the radiator....
You flushed the block (I believe still without removing freeze plugs) and got allot of crap out of the block... Though without pulling freeze plugs there is likely still crap I the block...

But while the debris in the block could still be causing problems I gonna focus on the radiator, after flushing the block has the radiator been either replaced or professionally rodded out? Back flushing it with water often doesn't remove hard debris that has found it's way into the tubes....

Of 25% of the tubes have a chunk of rust stuck in the tube your engine is gonna get hot... Period end of story...
 
Builderguy said:
Keep plugging away but I would pull back from the thin wall over bored idea. When turning 7-8 grand (or more) the motor puts out a ton of heat, and the cooling system can handle that so another 10 off the cylinder wall I would not expect to cause any cooling issue. Durability Yes, cooling No.
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I agree thin walls aren't likely the problem, thin walls can cause heating issues but that would show up under higher power output levels not normal driving...
 
1 Wild R/T said:
I agree thin walls aren't likely the problem, thin walls can cause heating issues but that would show up under higher power output levels not normal driving...
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Another (2nd) brand new Griffin Alu radiator installed. It did not make any difference. As far as debris from the block, I also thought that was the cause of the problem initially but after completely cleaning everything out (and I mean until it was completely 100% clean with nothing but clear distilled water flowing) and installing a see through coolant filter and then installing a another new radiator, same issue. Only now it takes longer to build up the heat but never-the-less, the heat still keeps creeping up and up, very slowly. Once it passes about 210 and appears to still be climbing I shut it down. With a 180 thermostat (yes it's new (x3) and yes I tested it before I installed it) the temp shouldn't be exceeding 200 regardless, in my opinion.
Sorry if I seem frustrated about things I've already checked over and over and over again. :)
Glad to hear comments that people don't think it's the block. Hey maybe if I get a radiator as big as the car itself and hook it up to one of those wind tunnel fans, maybe that would do the trick ;) Sorry, had to let out some sarcasm before steam comes shooting out my ears ;))
 
What I'd really like to know, at this point is, using the laser temp gun, what temp readings should I be seeing around the block, heads?, and radiator when it's getting too hot?
 
My two row ECP radiator with fan, clutch, and shroud removes about 15 degrees of heat at idle. The upper hose will measured 190 to 200 and the lower 175 to 185. Again that is at idle.
I use the business card trick to gauge flow. At idle a business card should stick to the upper left and right corners of the front of the radiator.
My dad used the spray bottle technique. He would spray the left and right tanks with the Windex bottle and make certain both tanks evaporated quickly.
Also, a overflow bottle may take you down 10 degrees. This allows almost 2 additional quarts of coolant, and reduces air and cavitation from the water pump area.
 
Trust me, I get your frustration... I think everyone who plays with old cars as found themselves stuck dealing with the overheat from hell... I work on a decent number of old cars still & back when it was my daily job I dealt with it constantly.... Trying to help over the internet is one step removed from diagnosing over the phone...

You've done most every possible thing, hate to say it but at this point I'd do more testing...you have the infrared heat gun, you need to get temperatures at various locations...

Thermostat housing.... Should stay very close to the thermostat setting..

Upper radiator hose..
Lower radiator hose..
You should see a 30-40 degree drop from the upper to the lower radiator hose..

Various points on the radiator core.. Cooler areas are not flowing.. It should be uniform from side to side but cooler at the bottom than the top..

For the following points read cast iron/aluminum not the valve cover..
Front of the heads...
Back of the heads...
If you can get to them the sides of the block...
Looking for hot spots which indicates lower flow... The rear always is a little hotter than the front but not allot... It should be uniform, no real hot spots... If your reading the heads & get to close to the exhaust ports those are definitely hot spots.. LOL

Oh, the number to consider critical is around 250-260.. Modern cars don't even turn on the computer controlled electric fans till 221 degrees...

If you temp gauge matches what your infrared gun tells you I'd probably go for a drive & when the gauge shows 230+ I'd stop & take my infrared gun & take readings..
 
Thanks Bill and R/T. Yes, I'll do some more testing and document detailed temp readings at all the various points mentioned. I'll post what I find. It may be a few days before I get to it. Sometimes I just need to take a break and walk away from it for a while. I'm sure you guys know what I mean.
 
RRDon said:
Yes, I already did that and actually, it worked better with the electric fan & shroud, I suspect that's because the electric fan runs at higher rpm and pulls a much larger volume through the radiator. It really moves a lot of air. However you gave me an idea about something else I can try. Thanks.
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IMO...
Most, if not all, electric automotive fans have a propeller as the air moving mechanism. The biggest problem with propeller fans is their static pressure capabilities. A prop fan, when presented any air flow resistance (static pressure usually measured in inches of water or WC.), to its air flow capabilities, will "pull back" or reduce its overall CFM air flow characteristics, for a given prop diameter. IF you could see the fan curve for a particular fan, which would include the propeller diameters, the RPM it's being operated at, in graphic format, you could instantly see its capability. CFM is plotted on the horizontal axis and static pressure plotted on the vertical axis and the propeller diameter shown in various increments.
As an inducement to purchase a specific brand/model of fan assembly, the company presenting the offering will generally list the max CFM the fan at zero static pressure, which is the maximum air moved, because its lists the biggest number. The potential buyer would then select this particular model, based on a non-obtainable value. As soon as the assembly is placed in front of the radiator, the fan is presented a static pressure value due to the fins and tubes of the radiator and the overall CFM's will be reduced. IF, the fan is placed on the "HOT" side of the radiator, because the fan is now handling hot air (at a higher static pressure) and the temperature of the air must be factored in (because the air is hot, its density is lower, and density is measured in pounds/hr, corrected for temperature) resulting in more pounds/hr or CFM's are needed. CFMs are corrected for standard temperature and pressure conditions. Often, this new number is considerably more.
In additional consideration is the physical size. IMO, a single fan installation is always better than multiple fans, due to the larger area presented, IF space constraints allow.
Just my opinion of course. I'm sure others will disagree.
BOB RENTON
 
Did you ever ascertain the temp gauge is reading correctly? Try the IR sensor. This crap would drive any normal person insane, feel your pain.
 
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