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Old 05-30-2009, 07:20 PM
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Pontiac 400 running hot

Hey all,

I have read through all of the threads that I could find on this site and tried some of the tips suggested in order to keep my pontiac 400 cool. I have a 1975 Pontiac Trans Am with a 400. The 400 has a 4 core radiator with a standard water pump. The 400 motor has 350 pontiac heads on it (this was done before the car became mine). The cam was in the car when I received it, and the previous owner does not know the spec on the cam. It may have been a cam out of a circle track car?

The timing is at about 10 BTDC and I believe it is around 34 at 2800RPM. There are two electric fans that are pulling air across the radiator. Both of these fans have their original shrouding. I believe these fans were off of a 1990's Ford Escort (This was done before I received the car).

Currently there are no inner fenders in the car so I believe that there is not a lot of airflow restriction under the hood. The thermostat I had in there before was a 160 and kept the coolant temp between 200-220. I thought that installing a 195 thermostat may help cool the engine better because the coolant is in the radiator longer, but the engine still runs around 200-220.

I've ran the engine with the radiator cap off and it appears that the coolant is flowing well through the radiator (when the tstat is open). I've pinched the radiator hose while the tstat is open and it feels like there is a lot of fluid moving. I think the water pump may be around 7 years old. The divider plate for the water pump is present, along with the two sleeves.

I dont believe the carb is running lean because the tailpipe is somewhat sooty. I've tested the mechanical coolant temp gauge and it is spot on. I think there may be a slight leak in the exhaust header but I dont believe this would cause the overheating issues that are present. The engine becomes hotter when cruising around 60mph.

I am not sure where to go at this point. I was thinking of checking the TDC timing mark on the balancer with the motor's actual TDC position. I was also considering installing another coolant temperature gauge on the passenger side of the motor to see if the was some kind of blockage in the coolant passages. If there was a temperature difference from one side of the motor to the other, then I figured there may be a blockage. The only thing left that I can think of checking is if the cam gear and crank gear line up correctly.

What are pontiac's original operating temps?

Any suggestions would be great.

Thanks,

Ben

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Old 05-30-2009, 08:14 PM
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you need to change your waterpump and check the devider plate in relation to the veins of the waterpump. they should be within 1/8" from the veins, if not, your water pump isnt working correctly.
with this problem corrected, your car should run cool.
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Old 05-30-2009, 08:36 PM
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Also, if you are not running a thermostat, the water pump may be moving the water, through the engine, too fast to cool, and through the radiator too fast to get cooled. If this is the case, I would suggest using a gutted thermostat or a restrictor plate.

Bill

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Old 05-31-2009, 12:49 PM
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Quote:
Originally Posted by WDCreech

HAY MAN!!! ITS AGINST FORUM REGULATIONS TO POST PORNOGRAPHIC MATERIAL!!!!!

OAH BUT MAN IS SHE F**KING SWEET!
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Old 05-31-2009, 01:23 PM
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Thanks for the replies, I will take the water pump off and look over it / replace it. I will keep you guys updated.

Ben
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Old 05-31-2009, 03:21 PM
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There are 2 types of replacement water pumps. Those with stamped impellers, and those that are cast. The cast impeller pumps cool better than the stamped. It would be adventagious to find the right pump.

Bill
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Old 05-31-2009, 03:44 PM
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Yeah, I was looking at a Gates water pump. It looks like the impeller is cast and it is standard rotation.
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Old 06-16-2009, 03:27 PM
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Just to give you guys an update:

I replaced the water pump and adjusted the divider plate to bring it closer to the impeller. The sleeves with the rubber gaskets were present and looked to be in good condition. After driving the car for about 25 minutes, the car was running around 230. I think the temp on the car is higher now because there is not a much safety as with using a 160, so the engine heats up faster.

At idle the car hangs out around 210 after being driven for 25 minutes (this was on an 85 day). I put a small fan right in front of the radiator to see if this would drop the temperature at all and there was no effect.

The next step will be to remove the electric fans and replace with a solid mechanical fan with the original shrouding. The more I think about the electric fans, the more I think they are probably not moving enough air through the rad. I am also going to put the inner fenders in the car and see if that affects the airflow through the radiator and highway speed.

I'll keep you guys posted.

Ben
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Old 06-16-2009, 10:09 PM
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Quote:
Originally Posted by zipfactor
Just to give you guys an update:

I replaced the water pump and adjusted the divider plate to bring it closer to the impeller. The sleeves with the rubber gaskets were present and looked to be in good condition. After driving the car for about 25 minutes, the car was running around 230. I think the temp on the car is higher now because there is not a much safety as with using a 160, so the engine heats up faster.

At idle the car hangs out around 210 after being driven for 25 minutes (this was on an 85 day). I put a small fan right in front of the radiator to see if this would drop the temperature at all and there was no effect.

The next step will be to remove the electric fans and replace with a solid mechanical fan with the original shrouding. The more I think about the electric fans, the more I think they are probably not moving enough air through the rad. I am also going to put the inner fenders in the car and see if that affects the airflow through the radiator and highway speed.

I'll keep you guys posted.

Ben

Ben,
A mechanical pump will take 7-13 horsepower to turn,thus making the engine work harder, and inner fenders will keep cool air from being able to cool the outside of the engine. There are dual electric fans, w/shrouds, that move over 3000 cfms, which, I think, would work the best. Also, Summit or Jegs list a thermostat switch to turn the fans on at 160 degrees and off at 140 that goes in the water cross over. In my drag car, I run this set up in conjunction with a 3-way switch. ie; water pump on/automatic/both water and fan on. Currently, I am running a single 16" 2000 cfm fan, but will probably upgrade to dual 10".

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Old 06-17-2009, 12:20 AM
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That's one B-A-D Poncho Mr WDCreech.
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Old 06-17-2009, 09:06 AM
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WDCreech,

Does this sound like an airflow issue to you (fans not pulling enough air across the radiator)? I would eventually like to go with a nice dual fan setup from summit/jegs but its not in the budget for the near future. Thanks for the replies.

Ben
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Old 06-17-2009, 11:06 AM
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Quote:
Originally Posted by zipfactor
WDCreech,

Does this sound like an airflow issue to you (fans not pulling enough air across the radiator)? I would eventually like to go with a nice dual fan setup from summit/jegs but its not in the budget for the near future. Thanks for the replies.

Ben
With dual Escort fans, there should be plenty of air moving through the radiator. I've wracked my brain, and can't think of what might be causing your problem. Have you tried playing with the ignition timing? Even though 34* sounds like enough, it could be a little slow at full advance. I have run at 40-42, but that was when we could get good gas. Also, do you know where your cam is installed, advanced, retarded, and how much? This shouldn't be your problem because if it were, you would be having other signs of drivability problems.



Bill
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Old 06-17-2009, 11:24 AM
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When a motor gets hot at low speeds it usually an airside of the radiator issue, that is, not enough air flow. A big misnomer when it comes to speed of flow of coolant in the radiator. Any time the coolant is flowing through the rad, it is being cooled, time spent in the radiator is irrelevant. Also using electric fans from small cars like an escort on a motor making HP is not going to help. Those fans were meant to cool a 4 cyl motor. How will they help with double the cyls to cool. Go to a Spal fan.
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Old 06-17-2009, 11:35 AM
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Have you reverse flushed the cooling system?
Is the lower hose in good condtion? Might be collasping.
Does it have the wire spring inside it?
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Old 06-18-2009, 07:58 PM
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I have always heard that the solid 7 blade mechanical fan with the original shrouding was the way to go. I am leaning toward that route because I dont have the money to spend on an expensive spiral fan at the moment.

I have not reverse flushed the system. The lower radiator hose is in good shape and has the spring in it.

I would also like to point out that it does get hotter while crusing (~60mph), so it is not only overheating at idle.

I have not checked how the cam is installed, but I remember when helping put the motor together the cam was installed straight up. I dont have any driveability problems but it is sluggish, and I guess this car used to run really quick (conversation with the previous owner).

Thanks for the replies.

Ben
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