I have a 69 Pontiac 350 overheating at idle.

I turned it off as it climbed through 240. 80 Degree day: driving it goes to 190-200. Then at a stop light that thing starts climbing immediately. If you have to wait more than one light cycle your are freaking out watching that gauge climb and climb. Then you drive it drops back off pretty quickly. I sat in the driveway when I got back and watched it continue a steady climb without an end is sight.

Background:

1 Newly rebuilt at .030. First miles on the motor. Edelbrock Performer intake and Edelbrock Carb.
2 New Large 3 or 4 core Aluminum Radiator.
3 Fan Shroud Installed.
4 Clutch Fan 5 Blade.
5 AC but the system hasn't been charged yet and I had the blower off.
6 Tested my Thermostat and it works good and opens right at 180 degrees.
7 Took off the water pump and decreased the gap between the filler plate and the pump fins to 1.5 mm. The gap was around 1/4 inch or more. They say this caused cavitation in the pumps, especially at idle.

I need to do a compression check.

My whole engine bay seems like it is hotter than hell. My AC compressor is fire hot after the car is driven. As well as everything else under the hood. My fuel line is really hot too and I think my fuel is boiling or close to it. It really bubbles in the filter even after I shut off the motor. I rev the motor and it drops about 10 degrees, release it and it goes right up again.

What else can I check or am I missing? I am not sure what the vacuum lines have to do with cooling but I have seen things discussing it on the net. Anything for the vacuum lines using an Edelbrock 4bbl 650 cfm carb?

Thanks,

SAM

I would look at the tune first off. Timing. Lean fuel can easily cause heat issues. I have even seen silicone sealer clogging up water passages on fresh rebuilds causing overheat conditions. Are you sure the clutch fan is working properly?

Ditto what Bob said above.

Sounds like you have a decent cooling system setup that should easily keep a 350 cool. So we're looking for major problems here, not little things like a better fan blade or a different thermostat.

With the car cold, take off the radiator cap, start the car, and while the car is idling, with the radiator cap off, watch to see when it gets to operating temp (180 in your case), and you should see coolant begin flowing in the radiator. If it flows, that eliminates a few problems, like a clogged heater core, plugged water passages, or a defective water pump.

If the coolant is circulating, next check your timing. If you've set the timing to spec, try this....

Loosen the distributor clamp a little, and with the engine idling, turn the distributor to advance the timing. If the idle goes up and smooths out, turn the distributor some more. Keep going until you hear a slight miss, then back off the distributor a bit until it doesn't miss, then tighten the clamp. Why fiddle with the distributor this way? There's a possibility your harmonic balancer ring may have slipped, which will make setting the timing with a timing light impossible. So now, if moving the distributor a significant amount smoothed out the idle, you may want to see if your overheating problem continues.

If moving the distributor did not smooth out the idle, then check to see where your vacuum advance hose is plugged into. Find a carb (or manifold) port that gets full vacuum at idle, and use that one for your vacuum advance. Using full vacuum frequently solves many overheating issues.

More things to check, but try these few tips first...

Mike

I will be able to try these things this Saturday. I really appreciate the help. The car is done and restored and I can't even drive to the bank and back. Very frustrating.

I will also put up pics of the fan and shroud area. I have a brand new fan and clutch assembly but I have learned that doesn't mean much. I had a brand new AC compressor and a new steering box but they were bad out of the box also.

With the heater core thing above, would there be anything specific to the Vintage Air System I put in? I did install one and when it was first charged the compressor smoked up and they thought it was the clutch. You could drive it without the motor on but when you turned it on it would heat up and start smoking.

Just thought I would let you know. Also, I do have the wire coil inside the lower radiator tube.

Thanks again and I will update this weekend.

SAM

One other thing, does anyone have an Edelbrock 4bbl 650cfm? If so what ports do you have the vacuum attached to for the vacuum advance and the other one that heads off to the transmission TH350?

Thanks,

SAM

Attach the vacuum advance hose to the lower right hand [as you look at it from the front] vacuum port.
This is manifold vacuum, the one on the left is stepped. Having the vacuum advance on manifold vacuum will result in more advance at idle, IF your vacuum advance can is working. My car idles cooler with more advance at idle. If your timing is too retarded the fuel air charge may be burning as it's going out the exhaust port which will induce a lot of heat to the water jacket surrounding the port. May turn your pipes red as well.
That may have nothing to do with your problem but who knows?

manual

Unfortatuely that's the tuning manual and it does not address the various ports to help with the vacuum lines. Here:

E-Brock 650 CFM Install Instructions

Questions I still have:

1. If you have AC, do the upper and lower baffles help with overheating at stop lights or just at higher speeds?

2. What is the correct diameter sizes of the water pump pulleys for an AC car? The reason I ask is that some folks think that my water pump may be spinning too slowly and not circulating my water through my Becool Radiator.

3. What is a reasonable temperature range for my 350 motor to idle at during a stop light? What is considered normal and what is too high?

4. I don't have a cast pump but I did fix the divider plate spacing, how much difference would the other pump make? I mean is it a must do?

5. I have a 180F thermostat and I think I read that the 69 350 with AC needs a 195F would this make my car run hotter or cooler having the 180F?

6. Lastly I have a 6 blade, clutch, 19 inch blade on my fan. It called for a 19 1/2 7 blade, is this a must do?

1. Yes. The baffles create a tunnel from the front bumper to the radiator. Otherwise, hot underhood air could be pulled back through the radiator.

2. The link below provides descriptions and sizes for all the factory pulleys:

First Gen Pulleys

3. I will leave this question to others. I believe some say above 220 is too hot. Otherwise whatever temp the factory set the idiot light to turn on at, as obviously that is what the factory engineers considered too hot. Unfortunately, I don't remember what that temp level is - although I know it has been mentioned on the site before.

4.The divider plate spacing is more important than the impeller. I would not change the water pump out unless you have exhausted everything else as it's a pain to do.

5. My opinion is as long as you do not have a 160 in there, you are good to go. On the other hand, if the Pontiac engineers said 195, then...

6. I would consider that a must do. Those 7 blade HD fans pull a LOT of air. I would definitely try that before changing out the water pump for one with a cast impeller.

I am an engineer by trade, and it is a bit frustrating when you put your skill into something and then the users just find a way around it...

My definition of engineering is "The study of human stupidity and the design efforts to try and eliminate it".

Do you any recommendations of which fan and clutch combo to use?

I see a bunch of fans available at places like Classic Industries but I don't know if I need a flex fan or OEM or a non-thermal clutch or the thermal clutch?

I have a new clutch but for the life of me I can't remember which I have? I had someone tell me that the fan should spin freely while cool but when the engine is warmed up and then turned off it should be locked up
until it cools. I tried that and my fan spun freely even though the temp of the coolant was at 230F. The engine seemed hotter than hell. The fan seems to pull air pretty well at idle so I am not sure if I have an issue with my clutch or not.

Thanks for the input.!

I like the OEM 7 blade 19.5 inch with factory thermal clutch.

Yes, the fan clutch should be disengaged when either cold or at highway speeds:

How a Thermal Fan Clutch Works

So where the heck can you buy these??? I have been looking all day.

My clutch seems to never engage. It spins freely when cold or hot. I had temps approaching 230F and shut off the engine and immediately spun the fan and it was free. Doesn't that mean it is not working properly?

If you can spin your fan freely after shutting off a hot engine, then yes, it sounds like your clutch is shot. That could be your whole problem.

If you have a non-thermal, it's controlled by rpm's. At idle, the clutch is locked up, and provides the most pull on the radiator. As the revs go up, the clutch begins to disengage, as you don't need a solid, locked up fan at highway speeds.

If you have a thermal, then you'll see a curly spring in front of the clutch. When temps get hot, the spring engages the clutch, and the fan is locked up. As the revs increase, the thermal clutch behaves like a regular clutch fan, and will nearly freewheel at highway speeds.

I've used the thermal clutch by Hayden. You can get them through O'Reilly's or any auto parts store, or you can go through mail order like Summit: http://www.summitracing.com/parts/hda-2747/overview/

Not sure of the factory fan will bolt up to the Hayden clutch. I bought the Hayden 18" black fan when I bought the clutch. Been using it for many years now.

A rule of thumb on your current clutch fan:

- When the engine is cold, and the engine is off, if you can flick a blade with your hand, and the fan spins more than 1/2 a revolution, the clutch is starting to go. If the fan spins an entire turn (or more), then the clutch is shot.

- With the engine hot (at idle), shut the car off. The fan should stop immediately. If it continues to spin a few revolutions, the clutch is shot.

Mike

I have the thermal clutch installed. It doesn't spin freely or without resistance when cold. I just got back from out of town and went out and tried to spin it. It moves but stops quickly. Which it should because it has only about an hour or two of running on it. Tomorrow I will run the car and get it warm again and see how it does. As I mentioned last post or so, when the engine was very hot and almost overheating I turned the ignition off and the fan acted as it does now and I could move it. As I also said, someone said that it should remain engaged until it cools and it would not cool immediately.

I will also try and check my timing and see if my advance is working. That is one of the only items I did not replace from the engine. Seems stupid now. I have an aftermarket 18" 6 blade fan but I don't know if it is worth trying to hunt down a 7 blade. I am trying but I can not find any anywhere. Where do we get these OEM 19 1/2" 7 blade fans?

Also, I just looked up the pulley sizes needed on the chart that was recommended and I think I have the wrong sizes. My car was originally a non-AC car and only had Power steering. So when I go into the chart that is listed here Belts and Pulleys . It looks like I may have the wrong Water Pump pulleys. I may have 8" pulleys instead of 7 3/16 (see last page 69 Firebird, V8, Power steering vs AC Power Steering. Would that make much difference?

SAM

If you determine that your fan clutch is shot, I got the a new OEM type from Spott's Performance.

You might want to try Frank's Pontiac Parts in CA for the 7 blade fan. They just happen to have a correct '67 one right now for $65 including the fan clutch.

I saw one last night that says for a 67. Would that matter? Hard to believe it would unless the pitch of the fins are different.

PY sells a nice one. Part # RPE67A

And Inline Tube sells the correct spacer if you need that too.

Thanks, but that is for a flex fan. I don't want a flex fan. I have heard about them distorting over time. I'm sure they are okay but I rather have something closer to OEM.

Um, 19" flex fan is 100% stock for 400 cars. Have them on all of mine, and not one car overheats.

Most 350 cars came with a four bladed fan.

Good luck!

Sorry, I didn't mean anything bad by it. I know that a 400 used a Flex Fan. I have heard "things" about the new lighter weight aftermarket fans being an issue. The info I found about the original fan says it is a "Heavy Duty Power Flex Fan". I figured they were made a little better than todays knock offs.

Here is a link to the Fan options and requirements.

Fan Options for 1969 Firebird.

Check with Franks Pontiac Parts. They seem to have a fair amount of original '69 equipment.

I will check with Franks. I also saw some on Ebay that are part number 9796134.

Also, I have the 8" diameter water pump pulley that was on the car prior to adding AC. Now according to the chart it calls for a 7 3/16" pulley on the Firebird. It also shows 6 1/2" for other Pontiacs. I can't seem to figure out why one Pontiac V8 would be different than a Firebird or Tempest V8?

Which pulleys should I get?

Pulleys and Belts

Since my temp cools off quickly after the light flow troubles seem to be an issue as well as the fan, shroud and baffles. I have adjusted my shroud and I am in the process of getting the upper and lower baffles. I still haven't decided if I want to pull the water pump and put the cast one on yet.

SAM

I wouldn't sweat the minor difference in fan size or 180 verses 195 thermostats. My pontiac 400, with a 180 thermostat ran 180-185 almost 99% of the time. The temp did not go up at red lights or idling. It didn't get hot drag racing, even with 4.10 gears and #16 heads.

I worked with a man that diagnosed thermal fan clutches old school. He would drag his hand along the back side of the fan with a red rag protecting his hand. He would apply drag to the fan, on a hot engine, at idle. If the could easily stop the fan from spinning, the clutch was bad. If he couldn't, clutch was good. It sounds crazy, but he was never injured or hurt, and he was a great mechanic. There was an art to applying gradual friction to the fan in the opposite direction of the fan rotation.

Please don't try the above with a flex fan and cut your hand off. Flex fans are loud.

Your clutch has to be bad. If your pulley size was the issue, you should be able to quickly tell. Advance the idle to 1200 tmp with your foot at idle (in netraul). Is the temp still skyrocketing at idle? If it doesn't climb with the higher idle, it is the pump speed! But, I bet it still gets hot until you get a working fan clutch.

I would for sure use the OEM 7 blade 19.5 inch with factory thermal clutch and use the baffles top and bottom if you have A/C, they do make a difference and I would also use the smaller Water pump pully (6 1/2) along with a Flow Kooler water pump. Make sure the plate between pump and timing cover is as close as possible to the pump. There is a link to that HERE They all make a big difference when put together and helped me out a lot with my cooling problems. I also put a 3 row alumn radiator in since my stock 4 row was shot. Now before I started my rebuild my temps stayed at about 10 degrees warmer than my thermostat in NC summer humidity and it didnt matter if I had a 160 or 180, so now I will run a 180, since in the winter time the 160 was too cold.