#41  
Old 10-10-2006, 01:00 AM
engineer engineer is offline
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no true flat top piston with 670 heads will give 9.48 compression. using a dished piston might, but there is no flat top one that is not custom which will work. so that said, means you need higher octane gasoline and richen the mixture. If a box fan in front of radiator does not lower temps, a change in fan type or blades will not be any better. IR gun the entire radiator and see what the temps are from top to bottom as well as top and bottom hose. I suspect hoses are collapsing and water flow is restricted somewhere. also check temp on heater hoses as well. you are running a heater?

  #42  
Old 10-21-2006, 03:16 AM
Alumitech Alumitech is offline
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There have been alot of good post here ...there are a few things to think about ...the suggestion of the infra read gun is good .. I dont trust gages completly ...if your temp sending unit is in the head the readings could be tainted as much as 15 degrees ... so you could be freeking over false readings ... the i/r gun will show truer readings .. hit the t/stat housing with it and check it against gage readings .
you should see a 30 degree temp drop from in let of the rad to outlet also .
this will tell you if the rad is doing the job with proper air flow .
my thinking here is a CFM problem and maybe water flow ...but normaly sitting still and high temps equate to low cfm trough the rad .
G.M had it right with a good thermo clutch and fan ..trying to out think that can be a problem .. short of Going to electric fans for high cfm at idle .
keep in ming its a 30 over and a tight motor 200 degrees may be expected at stand still for a while
ok here is the boaring read
hope it helps
Don
Cool solutions

You know what’s going to happen. You’ve been here before. You’re stuck in traffic, and the temperature gauge is doing that inevitable slow climb—210, 220, 230 degrees. Hot rodders seem to put up with cooling-system problems as if they were some kind of divine curse that must be endured. Forget that! Even in the mix ’n’ match world of Hot rodding, applying a couple of the simple ideas can help you build a cooling system that will perform best when you need it most.



Airflow
starting with the most basic system, an engine-driven mechanical fan and a radiator. The fan is designed to create negative pressure behind the radiator to pull air through. But the farther away the fan is from the radiator, the less effective it becomes. the fan blades be within 1 inch of the radiator and no more than 2 inches away. But that may not be enough.
Most street-car overheating problems occur at low vehicle speeds because of reduced airflow through the radiator. The best way to combat that is with a fan shroud. A properly designed fan shroud acts like a wind tunnel in pulling air through the radiator. The best shrouds are designed to pull air from the entire radiator rather than just in the center around the fan.
fan blades should be positioned so that approximately ½ of their depth projects into the shroud and fan-tip-to-shroud clearance be ¾ inch. Reducing that clearance will pull the maximum amount of air through the radiator, especially if you are using a fan with a significant pitch-angle blade. A tighter tip clearance is better, but it must allow for engine/chassis movement. Generally, the larger the pitch angle of the blade, the more air the fan will tend to pull through the radiator, especially at low speeds.

The shroud can act as a restriction in some cases such as some shrouds with electric fans since the air must funnel between the fan and the shroud. If you need a shroud to prevent low-speed overheating, you could create spring-loaded pressure-relief doors in the shroud, which would open as pressure increases inside the shroud at high speed.

The larger pitch angle of the fan blade pulls more air but requires more power to do so. different engine-driven fans with different pitch angles. high-fin-density radiators (16 to 20 fins per inch) work best with low-pitch-angle-blade (electric) fans. Low-fin-density radiators (10 to 14 fins per inch) work best with engine-driven fans with a steep blade angle. Some experimentation may be required to determine the proper pitch angle for your radiator.
a large engine-driven fan with a large pitch angle with out a clutch could become a restriction at high rpm and act like a large, flat disc that reduces airflow.

electric fans should always be mounted behind the radiator for optimal cooling. These fans do a better job of creating a low-pressure area behind the radiator than they do of pushing air through a radiator.... switching a 12-inch electric fan from in front of the radiator to behind it will increase airflow by a solid 10 percent, based on a 70-percent coverage of the radiator with the fan. A 16-inch fan would increase airflow by 15 percent.

One other point worth mentioning is that the air must be able to escape the engine compartment once it has passed through the radiator. Extremely tight engine compartments might contribute to overheating problems because the air cannot easily escape the compartment. That could also contribute to a high-speed overheating problem, creating high pressure under the hood, which would block airflow through the radiator. That was the one of the reasons for hood louvers in street rods.

The larger pitch angle of the fan blade pulls more air but requires more power to do so. different engine-driven fans with different pitch angles. high-fin-density radiators (16 to 20 fins per inch) work best with low-pitch-angle-blade (electric) fans. Low-fin-density radiators (10 to 14 fins per inch) work best with engine-driven fans with a steep blade angle. Some experimentation may be required to determine the proper pitch angle for your radiator.

Brass copper and aluminum radiators

Since brass and copper are very soft, larger tubes cannot handle the pressure. Aluminum radiators, such as those available from Alumitech can be built with tubes up to 1- inches in diameter. The larger tubes allow the radiator manufacturer to place more fins-per-inch, which improves the radiator’s thermal efficiency. That reduces the thickness (and weight) of the radiator and also improves airflow through the radiator. For example, an aluminum radiator with two rows of 1- inch coolant tubes is probably more efficient than a four-row brass/copper radiator. Not only would the brass/copper radiator be heavier, but its added thickness would present a more restrictive path for the air to travel, especially at low vehicle and engine speeds.
To put that another way, it is possible that replacing a three-core brass/copper radiator with a four-core brass/copper unit might actually reduce cooling efficiency at low speeds, especially if airflow through the three-core unit was already marginal based on identical fin densities. That’s because the increased thickness created a greater pressure drop across the radiator, especially with no shroud. You could make the four-core radiator work, but it would require improvement of airflow management with a shroud, a bigger fan or both. In other words, a thicker radiator is not always the answer to an overheating problem.

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Last edited by Alumitech; 10-21-2006 at 03:23 AM.
  #43  
Old 10-21-2006, 08:39 AM
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jjscerbo jjscerbo is offline
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Seems to me that what you have is a low circulation proble at idle. You may want to play around with pulleys to speed up the water pump.

Something else to concider, You may have some combustion pressures entering the cooling system. The pressures may interfere with circulation. Either look for bubbles in the radiator neck while idleing or attach a radiator pressure gauge to monitor rapid pressure increases. Could be due to an overlooked crack in the cylinder wall or combustion chamber.

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  #44  
Old 10-21-2006, 10:58 AM
Alumitech Alumitech is offline
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Quote:
Originally Posted by jjscerbo
Seems to me that what you have is a low circulation proble at idle. You may want to play around with pulleys to speed up the water pump.

Something else to concider, You may have some combustion pressures entering the cooling system. The pressures may interfere with circulation. Either look for bubbles in the radiator neck while idleing or attach a radiator pressure gauge to monitor rapid pressure increases. Could be due to an overlooked crack in the cylinder wall or combustion chamber.
yes this is one thing I forgot to mention .. and a good point .. you can have the coolant tested for hydro carbons to see if you have a head leak .. I have see guys going trough what you have chasing this gost ... only to find that problem later ..good advice .

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  #45  
Old 11-22-2006, 12:03 PM
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Region Warrior Region Warrior is offline
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Anyone changing to a flex fan. Get a 19".
I have found that placing it 1/3 into the shroud will make it almost 1/2 way in @ idle. Never had a proplem in 30yr's.

As the others have said, as long as you have good air and water flow, fuel and timing are usually the problem.
After setting timing, try ajusting the idle mixture with a vacuum gauge.
Shoot for a steady needle at the highest reading.
You may find it idles smoother at a lower vacuum reading then whats considered ideal.
For instance, on my car, i can get 14", but it runs better/smoother @ 12-13". The needle is more steady.

A good free flowing dual exhaust helps alot also.
I havent noticed a difference with octanes @ idle, but for street i have stayed under 10-1 comp.

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  #46  
Old 12-16-2006, 09:46 PM
Indiangoat Indiangoat is offline
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Default Overheating Problem.

Here are a couple more tricks to reduce engine temps in these old pontiacs.

1. Insert a brass plumbing nipple in the heater hose tube at the firewall. This will reduce the diameter of the heater hose outlet at the firewall, reduce the flow of hot water through the heater system, and divert more flow to the radiator where heat exchange can take place.

2. Make sure you are not running lean. Don't forget, if the carb was designed for EGR, not running EGR will cause lean condition. Also,Q-jets all begin with either "70" or "170", indicating a Rochester product. The "170" carbs are the newer ones, usually post 1974. Big difference is that the primary rods don't interchange between these two series carbs. Mix match primary metering rods between the two series may cause lean condition. The post 1974 rods are a bit longer and may not pull up out of the jet far enough. Reference:http://www.442.com/oldsfaq/ofcrb.htm[/url]

Other Good info:

Article by John Van Becay

Once again cruising season is upon us and many Pontiac owners are prepping their cars for the long hot summer ahead. Does your ride run a little hotter than you'd like? Are there occasions when that temperature gauge just keeps rising?
Many Pontiac owners are very knowledgeable about cooling issues. Their willingness to help others shows the camaraderie enjoyed by the Pontiac community. They know that none of us is as smart as all of us. In the same spirit we would like to share some of the cooling tips we have learned over the years. Perhaps having these tips in one place will help others with a difficult cooling problem.

Here are 10 tips to address with any overheating problem:

1. Many cars overheat from more than one problem. Often we assume a bigger radiator or a similar big gun solution will fix our problem. Maybe it will, but often by so doing you are addressing the symptom and not the cause. Many cars over the years pick up little annoyances that contribute to overheating. Individually none of them would overheat your car. Collectively you have an overheating problem. Look at the whole car when addressing overheating problems.
2. Before you do anything else, tune up the car. Many overheating cars are out of tune, Be dead nuts certain you are not running lean or with retarded timing.
A lean fuel mixture will overheat your car right now. If your engine runs lean you can chase your tail looking for problems in the cooling system and never figure it out. Be sure you are not running lean. The easy way to do this is richen your jetting a couple of steps. If the overheating is better, you're on the right track.
3. There is a lot of misinformation about ignition timing and cooling. Retarded timing contributes to overheating. Advanced timing helps cooling. Bump up your initial timing a few degrees and see if it helps the car run cooler. It's an easy and practical fix. Of course, if you advance enough to enter pre-ignition or detonation you will start to overheat. Detonation contributes to overheating. If you start to detonate back off the timing. Overheating cars should always run vacuum advance. Vacuum advance helps cooling.
4. Cars can overheat from coolant circulation that is either too slow or too fast. When your car left the factory it probably had the correct speed for the water pump. Over the years things change, pulleys are swapped, rear end ratios are changed, tire sizes vary. Your car may not have the right circulation speed for the water pump. Remember cars can overheat from circulation that is either too fast or too slow.
5. Look at your airflow. Be sure your shroud fits properly and is sealed to the radiator. What'd ya mean you don't have a fan shroud??!!?? If not, obtain a shroud before you do anything else. You can adapt a shroud from the junkyard or many after market suppliers can provide you one. Seal the shroud to the radiator with weather stripping.
6. The best all around fan is the factory design with a thermal fan clutch. Flex fans aren't as versatile, Solid fans pull lots of air but are noisy and suck horsepower when you don't need the extra cooling.
If you need extra air flow there are many electric fans on the market that can help. Be sure your charging system is up to the task of handling the extras amps from an electric fan.
7. Reduce the antifreeze in your coolant. A 50/50 mixture does not help cooling. Either run 100% distilled water with water pump lubricant or distilled water with about 15-20 % antifreeze. Either mixture will cool better than 50/50 and still lubricate the water pump and provide corrosion protection for your system. Remember when the weather turns cool to switch back to 50/50.
8. Use a better grade of gas. If you are not running premium and you are overheating, step up to the top grade. If there is no improvement, try advancing your timing a few degrees. The extra octane will allow you a little extra timing without getting into detonation. Many older cars and particular muscle cars were designed for better gas than is now available. If you are detonating on today's gas you can be overheating. Remember not all detonation is audible.
9. If you are running an automatic, install a quality after market transmission cooler. Cooling the transmission is added work for an already overtaxed radiator. Do not mount the cooler in front of the radiator where it will overheat the cooling air. Rather mount it to one side.
10. Notice your driving habits. The more gas you burn the more heat the engine produces. Jackrabbit starts followed by hard braking, constant acceleration, flogging the engine uphill, all burn lots of gas. Yes, these are performance cars and that's why we love them. We're not saying don't enjoy your car, but if you are constantly into the accelerator, you are producing extra heat that the cooling system has to get rid of.
All of these tips and many, many more are contained in our informative cooling manual. Our ordering info is below. Compared to the expense of buying parts in a hit and miss fashion to solve your problem, our book is a downright good investment.


Last edited by Indiangoat; 12-20-2006 at 11:14 PM.
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