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Discussion Starter #1
Ok folks I am looking for some help in engineering an "Out of the box" solution for a problem I have with my 66 Chevy II.
I have a 871 blown 355 in my car and I have good coolant temp control whenever the car is moving, not an issue, if I am driving, even at low speeds like 10 mph, she will keep the temp around 200. The problem is when I am caught in a stop and go traffic situation, I can hold out for maybe 20 - 30 minutes before it starts to run away and there is nothing I can do except turn her off and wait to cool down. I have an alarm set at 230 to warn me so I can take action to get out of the situation.

I have tried EVERYTHING, large radiator, dual fans with shroud, moved oil cooler from front of rad to another location, I mean everything I can think of but cannot solve this problem. I have had some say that I need a bigger radiator, but this would require moving all the other stuff up front to the trunk, don't want to do this as this is a street toy. There is just not enough room in the engine compartment for that. This is not a new problem, I have been dealing with it since I built the car in 99.
This is my new direction I am thinking about, I am planning to build a "Oh Sh%t" system for when I get caught in a situation where I have no choice but to shut her down.
My plan is to add a fogger system in front of the radiator to give the cooling system a chill and try to recover, even for a little while, until I can get out of the traffic or start rolling again.
Is this a good idea? Would NOS work for this? Is there a better way to get back under control of the temps?
Just looking for opinions as the car is in for paint now and I am planning to do Power Tour this year but have heard horror stories about the traffic on tours past.
I posted this on Facebook groups and received suggestions for my situation, tons of good information but as usual there are many opposing options so I need to sort through it all.

I know that one of the problems is airflow through the radiator when at idle and I need to address that.
The way I see it is that I have two issues, one is the heat generation in the engine, the other is heat removal in the cooling system, I need to find a balance I can live with.

My plan when it comes home from the paint shop is this,
1. Verify ignition timing curve. I have heard that I need to advance the timing and also that I need to retard the timing.

2. Look into better electric cooling fans. This is restricted to the space in the engine compartment and the fact that I have an 871 blower with large pulley and belt system. Many have said I need to go to a mechanical fan, can't happen with my setup.

3. Look into radiator construction, I have heard that I need a multi-pass radiator. I have now a single pass, 2 row B-Cool aluminum radiator. I have read quite a few posts on this issue and the same thing, many different options, pros and cons. Some say that I can get a 24 degree drop in the coolant returning to the engine but at a cost of reduced flow. Is this really a good idea?

So all you professional and shade tree engineers, please jump in and give me some ideas.
 

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Electric or belt driven water pump?

If belt driven, what size pulley compared to drive pulley?

Could be the pump is turning too slow at low RPMs.

Just a thought.

Rob
 

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"Some say that I can get a 24 degree drop in the coolant returning to the engine but at a cost of reduced flow. Is this really a good idea? "

No. Flow is king, and the reduction of the radiator outlet temperature caused by this will be accompanied by a rise in the inlet temperature. There's a reason that thermostats reduce the flow when the engine is cold. The advantage of a dual pass radiator is the increased turbulence brought on by the reduced flow area, but this advantage runs out at the point where the mass flow is impeded enough to limit the heat dissipation.

A friend of mine had a blown 355 in his 240Z with the same overheating problem. He had a single 16" Spal fan which wasn't doing the job. I installed a Taurus fan and he was good to go.
 

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Read that article,very informative. In your situation I would run the surge tank and overflow tank. Might consider a waterless coolant such as Evans as well.
 

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Do you have a hood on your car? If so, take it off and see if you still have overheating problems. If this solves it, you might be able to remove your inner fenders or install louvers in them to let more heat out. I was having issues with my Chevy II running hot when I was caught in traffic on the interstate this past fall. Out of desperation, I cut the nylon strap off of a rachet strap I had in the trunk. I popped the hood and tied the nylon strap to the hood latch mechanism so the hood was popped about 6" while I was driving down the interstate. Having the hood open about 6" either allowed more air to go through the radiator or it let more heat out of the engine compartment, or a combination of both. While not an elegant solution, it got me out of an overheating situation and gave me some more info about my problem.
 

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Discussion Starter #7
Read that article,very informative. In your situation I would run the surge tank and overflow tank. Might consider a waterless coolant such as Evans as well.
What I have read about the Evens coolant is that it will stop an overheat/boilover situation, this is not my case, but it will increase the engine temp, this is what I am trying to overcome.
 

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Discussion Starter #8
Do you have a hood on your car? If so, take it off and see if you still have overheating problems. If this solves it, you might be able to remove your inner fenders or install louvers in them to let more heat out. I was having issues with my Chevy II running hot when I was caught in traffic on the interstate this past fall. Out of desperation, I cut the nylon strap off of a rachet strap I had in the trunk. I popped the hood and tied the nylon strap to the hood latch mechanism so the hood was popped about 6" while I was driving down the interstate. Having the hood open about 6" either allowed more air to go through the radiator or it let more heat out of the engine compartment, or a combination of both. While not an elegant solution, it got me out of an overheating situation and gave me some more info about my problem.
I do have a hood on the car but I have a large hole in it for the blower to come through. I also cut out the inner fenders, behind the shock towers to allow air to escape the engine compartment. I ran the car in the garage at idle, without the hood on and the same thing occurs.
 

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Discussion Starter #9
"Some say that I can get a 24 degree drop in the coolant returning to the engine but at a cost of reduced flow. Is this really a good idea? "

No. Flow is king, and the reduction of the radiator outlet temperature caused by this will be accompanied by a rise in the inlet temperature. There's a reason that thermostats reduce the flow when the engine is cold. The advantage of a dual pass radiator is the increased turbulence brought on by the reduced flow area, but this advantage runs out at the point where the mass flow is impeded enough to limit the heat dissipation.

A friend of mine had a blown 355 in his 240Z with the same overheating problem. He had a single 16" Spal fan which wasn't doing the job. I installed a Taurus fan and he was good to go.
I do know the real issue is reduced airflow at idle and I have to investigate replacing the fans I have now. The problem is lack of room with the blower belt and pulleys, need to do some research to find some setup that will fit.
 

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Discussion Starter #10
Electric or belt driven water pump?

If belt driven, what size pulley compared to drive pulley?

Could be the pump is turning too slow at low RPMs.

Just a thought.

Rob
I have a pulley setup that overdrives the pump a bit now, mechanical. Another idea is the pump itself, could it be possible the engine builder installed a reverse rotation pump on it that is designed for a serpentine belt setup. How do you tell if it is a reverse rotation pump?
 

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You said when the car is moving it's fine. But overheats at idle. That's just airflow. That's the number 1 thing you need to fix. Also make sure you're not running the idle too lean. Taking the hood off wouldn't help anything at idle, only at speed where you dont have a problem. One question though. If it gets hot, will it cool back down if you get moving?
 

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You said when the car is moving it's fine. But overheats at idle. That's just airflow. That's the number 1 thing you need to fix. Also make sure you're not running the idle too lean. Taking the hood off wouldn't help anything at idle, only at speed where you dont have a problem. One question though. If it gets hot, will it cool back down if you get moving?
Actually, with such a physically large motor under the hood, it can restrict air flow through the radiator and hold heat under the hood. A hood absolutely can cause it not to cool at an idle in extreme situations like this. However, since he has a large hole in the hood and cut large holes in the inner fenders to increase air flow, it doesn't seem to be his problem in this case.
 

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I have good coolant temp control whenever the car is moving, not an issue, if I am driving, even at low speeds like 10 mph, she will keep the temp around 200.
At 10mph, you are really not getting that much "natural" airflow thru the radiator vs what a pair of GOOD electric fans with proper shrouding are pulling (unless your dual electric fans w/shroud are of poor quality and moving very little air). To help determine if poor quality electric fan airflow is the issue, see if you can get/borrow a big industrial cooling fan and place it in front of your radiator. Turn it on when your coolant temps begin to creep above 200° while idling. If the temp begins to drop, your electric fans are not moving enough air.

When your car starts to move, your engine RPM's increase and your water pump turns faster... thus increasing water flow. What would happen if you are not moving at idle (engine temps start to increase above 200°) and you increase your engine RPM's? Does the coolant temp continue to rise?... or does it begin to come down? If it begins to come down, you may need a higher flowing water pump... or see below.

Another idea is the pump itself, could it be possible the engine builder installed a reverse rotation pump on it that is designed for a serpentine belt setup. How do you tell if it is a reverse rotation pump?
It is possible that the builder could have installed a water pump with the incorrect flow (based on the direction it is spinning when the engine is running). Does your water pump spin in a clockwise direction (standard flow water pump on sbc - usually seen with the drive belt contacting the upper side of the water pump pulley)... or does your water pump spin in a counterclockwise direction (reverse flow water pump on sbc - usually seen with the drive belt contacting the lower side of the water pump pulley)?
If a water pump was spinning the wrong direction, you would have very little coolant flow at idle. As you increased RPM's, you would gain some increased flow... but it would still be low compared to a "correctly flowing" water pump.
See if you can locate a part # on the pump... or contact the builder to see if they have this info. The only other way to determine the flow of a water pump is to remove the back cover and look at the pump vanes. The vanes should be tilted/curved in the direction the pump is spinning.

Verify ignition timing curve. I have heard that I need to advance the timing and also that I need to retard the timing.
Insufficient/incorrect ignition timing is something else that could cause over heating at idle.
*What type of ignition system are you running (HEI, CD, etc)?
*What is your initial timing set to @ idle?
*What is your total mechanical... and at what RPM?... or do you use a "locked out" distributor timing?
*Do you use a distributor with vacuum advance?... and if connected, how much additional advance is it providing at idle?... and if used, is the VA connected to the carb or the intake?
*Do you have any type of timing retard during boost?
 

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Discussion Starter #14
You said when the car is moving it's fine. But overheats at idle. That's just airflow. That's the number 1 thing you need to fix. Also make sure you're not running the idle too lean. Taking the hood off wouldn't help anything at idle, only at speed where you dont have a problem. One question though. If it gets hot, will it cool back down if you get moving?
Yes, as soon as I start moving it will come back down in a few minutes.
 

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Discussion Starter #15
What would happen if you are not moving at idle (engine temps start to increase above 200°) and you increase your engine RPM's? Does the coolant temp continue to rise?
Yes, here is a little experiment I did to see what the effect of higher rpm would be, sitting in the garage.
398454


It is possible that the builder could have installed a water pump with the incorrect flow (based on the direction it is spinning when the engine is running). Does your water pump spin in a clockwise direction
Yes, it is a v-belt drive pulley, crank, pump, and alternator only

The vanes should be tilted/curved in the direction the pump is spinning.
I always thought the coolant in came into the center and was forced out the outside of the vanes, this would be more efficient if it were the other way, right?


Insufficient/incorrect ignition timing is something else that could cause over heating at idle.
*What type of ignition system are you running (HEI, CD, etc)?
I am running a Holley Pro Strip Annihilator CD ignition, programmable curve in 500 rpm increments.

*What is your initial timing set to @ idle? I think it is still at 16 degrees

*What is your total mechanical... and at what RPM?... or do you use a "locked out" distributor timing?
I do have a locked-out distributor, all in 34 degrees at 2000 rpm.

*Do you use a distributor with vacuum advance?
No

*Do you have any type of timing retard during boost?
Yes boost retard based on boost sensor, 1 degree per pound of boost
 

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Discussion Starter #16
I do know there is an airflow issue due to the fans I am using but also wondering if there are other issues also, like ignition timing, water pump, etc.
I am making a plan of what to do when it comes back from the paint shop.
 

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I do know there is an airflow issue due to the fans I am using but also wondering if there are other issues also, like ignition timing, water pump, etc.
Based on the information you posted, I agree with the others that stated the lack of airflow from the electric fans while the car is not moving is the main issue.
If your water pump was not flowing enough volume (or spinning in the wrong direction), I would think the overheating issue would have continued as your car began to move forward... you stated the temps would begin to decrease as your car started to move forward.

I do not have any personal experience with sbc timing with superchargers... but from what I have read, your timing seems ok. Some like to run a little more initial timing at idle (20°-24°)... but they also had a way to retard the timing at start-up (plus boost retard similar to yours).
 

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Discussion Starter #18
Based on the information you posted, I agree with the others that stated the lack of airflow from the electric fans while the car is not moving is the main issue.
If your water pump was not flowing enough volume (or spinning in the wrong direction), I would think the overheating issue would have continued as your car began to move forward... you stated the temps would begin to decrease as your car started to move forward.

I do not have any personal experience with sbc timing with superchargers... but from what I have read, your timing seems ok. Some like to run a little more initial timing at idle (20°-24°)... but they also had a way to retard the timing at start-up (plus boost retard similar to yours).
Thanks Mike, I do have a crank retard wired to the ignition switch that comes in when in crank position so I guess I could bump up the timing at idle and try it.
 

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Ok folks I am looking for some help in engineering an "Out of the box" solution for a problem I have with my 66 Chevy II.
I have a 871 blown 355 in my car and I have good coolant temp control whenever the car is moving, not an issue, if I am driving, even at low speeds like 10 mph, she will keep the temp around 200. The problem is when I am caught in a stop and go traffic situation, I can hold out for maybe 20 - 30 minutes before it starts to run away and there is nothing I can do except turn her off and wait to cool down. I have an alarm set at 230 to warn me so I can take action to get out of the situation.

I have tried EVERYTHING, large radiator, dual fans with shroud, moved oil cooler from front of rad to another location, I mean everything I can think of but cannot solve this problem. I have had some say that I need a bigger radiator, but this would require moving all the other stuff up front to the trunk, don't want to do this as this is a street toy. There is just not enough room in the engine compartment for that. This is not a new problem, I have been dealing with it since I built the car in 99.
This is my new direction I am thinking about, I am planning to build a "Oh Sh%t" system for when I get caught in a situation where I have no choice but to shut her down.
My plan is to add a fogger system in front of the radiator to give the cooling system a chill and try to recover, even for a little while, until I can get out of the traffic or start rolling again.
Is this a good idea? Would NOS work for this? Is there a better way to get back under control of the temps?
Just looking for opinions as the car is in for paint now and I am planning to do Power Tour this year but have heard horror stories about the traffic on tours past.
I posted this on Facebook groups and received suggestions for my situation, tons of good information but as usual there are many opposing options so I need to sort through it all.

I know that one of the problems is airflow through the radiator when at idle and I need to address that.
The way I see it is that I have two issues, one is the heat generation in the engine, the other is heat removal in the cooling system, I need to find a balance I can live with.

My plan when it comes home from the paint shop is this,
1. Verify ignition timing curve. I have heard that I need to advance the timing and also that I need to retard the timing.

2. Look into better electric cooling fans. This is restricted to the space in the engine compartment and the fact that I have an 871 blower with large pulley and belt system. Many have said I need to go to a mechanical fan, can't happen with my setup.

3. Look into radiator construction, I have heard that I need a multi-pass radiator. I have now a single pass, 2 row B-Cool aluminum radiator. I have read quite a few posts on this issue and the same thing, many different options, pros and cons. Some say that I can get a 24 degree drop in the coolant returning to the engine but at a cost of reduced flow. Is this really a good idea?

So all you professional and shade tree engineers, please jump in and give me some ideas.
Some people are putting upper and lower radiator filler panels on their cars that overheat. They say to keep the airflow thru the radiator not around it. I have a 57 Vette that will do the same thing while in town. When stopped, I now put the transmission in neutral, but it's an automatic. Works until I get going it again. Someone also said if your car has a heater to turn the fan on. It works on my 62.
Good luck.
 

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Thanks Mike, I do have a crank retard wired to the ignition switch that comes in when in crank position so I guess I could bump up the timing at idle and try it.
Could the crank retard be programmed to not retard the timing once the engine is running? IE: turn off at 500 rpm. Then have enough timing for idle and a cooler idle temperature.
 
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