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Old 08-13-2011, 12:39 AM
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Overheating Help!!!!

Rebuilt motor 350 small block, bigger cam, new water pump, new radiator 3 core, changed the thermostat from a 160 to a 190. Radiator cap 16lbs. A six blade flex fan, in front of that I'm running a 14" electric fan also. No shroud, chrome, exaust headers, chrome oil pan, valve covers pulleys. What other possible issues can I be having. Originally I had a 2 core radiator with a pusher fan, kept the car from puking antifreeze, but the motor was hot. The new radiator was bigger I was not able to mount the spacer, so I tried the double fans. Could something possibly be wrong inside the motor? Timing and carb cause this much head ache. The car runs fine as long as its ran steady, once I hit a few stop lights I'm done. Seems to get hot very quick 190 in a couple blocks, 210-220 on the freeway, 230 plus if I stop at some lights, if the car is turned off when hot, its very hard to start back up unless cooled. The car is not smoking, I have asked everyone and anyone, mixed up now. Please if you got any tips

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Old 08-13-2011, 06:36 AM
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Gets too 190 in a few blocks; because the thermostat is 190, a shroud would be a good idea and maybe a 180 on the thermostat. I can only give you some stats to consider.

My car in the summer, 180 stat, motor open no side curtains. Driving 180 -190 in 90 - 100 degree weather, stop lights can drive the temp to 210, but when I start to move in starts to come back down. Just sitting at a light you have two things working against you. Close to other cars, no air space and the heat coming up from the pavement. The motor is inhaling all this dead air that is super heated from the pavement, that is not helping. A rule of thumb is the motor will average 100 degrees over ambient temps, if the motor starts to cool down when you start to move that is a good sign things are working for you.

Hard starting when hot usually is an indication of to advanced on the timing, might give that a check. Make sure the anti freeze is the proper mix, more anti freeze does NOT equal lower temps, for a fact plane water cools better. Some water pumps look nice but do not flow so well, just info on that comment. You sure there is no air in the system, there are products out here that advertise better cooling, I have never used them so I can not advise on that.

So there you have a few ideas and some things to check, I do not like the 230 that sounds on the high side, and at highway speeds is odd, that could be a collapsing lower radiator hose, that should have a spring inside of the hose to prevent that.
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Old 08-13-2011, 08:01 AM
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More than likely the timing is retarded.

Look at your exhaust pipes close to the exhaust manifolds. Are they glowing cherry red at idle? This is another indicator of a retarded ignition timing.

Check/set the timing with the vacuum advance hose dis-connected and plugged. Re-attach the vacuum hose after checking/setting the timing. If you are connected to a full manifold vacuum source you will have to re-adjust the idle RPM after re-connecting the vacuum hose.

Suggest setting the timing between 12-18 degrees BTDC with no vacuum added. Idle RPM should be below 800 when in DRIVE (if an automatic) or in NEUTRAL if a standard shift. 650-700 RPM is typical.

Another less likely reason for the quick build up of temps would be a very lean condition. Look for any vacuum ports at the carb base or on the intake that are open (not plugged off or hooked up). If any are found, plug them off.

The difficult re-start when hot is caused by the starter solenoid getting excessively hot from the residual heat off the engine. Correcting the timing should improve that.
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Old 08-13-2011, 08:36 AM
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ALL of the above ...



But I always run a shroud.
My car specs are:

350 ci with 430 HP.
Walker radiator
Walker shroud
6 blade mechanical clutch fan.
180 thermostat

The car runs 180 ... after warming up ...
In traffic, sitting still and down the highway.

A shroud will help your problem but you need to have the timing and fuel correct first.

Deuce ... MODERATOR
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Old 08-13-2011, 09:07 AM
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Might sound contradictory, but the electric fan in front of the radiator may be contributing to the condition rather than helping. A front mounted electric fan could cut down on the exposed area of a radiator. As mentioned already if you do not have a close fitting fan shroud you will be chasing your tail. As you might surmise I am not a big proponent of electric fans.

Vince
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Old 08-13-2011, 09:26 AM
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Quote:
Originally Posted by 302 Z28
Might sound contradictory, but the electric fan in front of the radiator may be contributing to the condition rather than helping. A front mounted electric fan could cut down on the exposed area of a radiator. As mentioned already if you do not have a close fitting fan shroud you will be chasing your tail. As you might surmise I am not a big proponent of electric fans.

Vince
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Old 08-13-2011, 10:14 AM
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Overheat Problem

Timing and mixture could be part of the problem but I also agree with the shroud suggestion. Over 35 to 40 mph the fan is pretty much ineffictive but below that the effectiveness of the fan is the key colling factor. As you mentioned, after a few stop lights the temperature climbs. Without a fan shroud, air will be coming in from numerous directions and not all of it from across the radiator. The shroud will direct the air across the radiator.

I drove my 1955 2nd. series with a small block 400 cu. in. engine in it across the desert 120 miles daily in So. Cal. for 10 years. That is inherently a very hot running engine in a very hot climate. A lot of the traffic was stop and go. The biggest single thing I could do to keep it cool was to ensure I had max air flow directed across the radiator and blocked off as many other air sources as I could from the engine bay to keep the water temp below 220.
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Old 08-13-2011, 11:25 AM
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Get shed of the flex fan. AT RPM the fan will go flat.. Just like putting a piece of cardboard the size of the fan behind the radiator. Air has a hard time getting past the flat fan.
Fan shround with a 'real fan that doesn't flex flat. Fan half way 'down in the shroud. Find a stock four blade fan. That should pull more air than needed to cool your ride.
Make sure the bottom hose isn't getting sucked closed. Lower with a spring or the fabricated hose with the spring in the hose itself.

The above posts are correct, check timing and how lean the carb could be.
Lastly one weird way to make sure your engine/radiator is full of coolant. JACK the corner of car, which has the filler cap, as HIGH as you can. Making it the highest point of the system. You'd be surprised how much more you can add to the system doing this trick.

Phil
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Old 08-16-2011, 11:21 PM
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If all else fails - try this.

All of the previous advise is good. My car had the exact same issue as yours and I did all of the usual things discussed here and it still would over heat. It turned out I had a blown head gasket, and it did not show up with a compression test. I would try the previous suggestions first and if that does not work try this.

To check for a blown head gasket, on a completely cold engine, take the radiator cap off, start the engine, shine a flashlight down into the radiator. After the engine runs for a few minutes, usually about the time the thermostat opens, keep your eye open for bubbles. I you have bubbles in the radiator, you either have a blown head gasket, or it could be a cracked block or head, but it is usually a head gasket.

Let us know what you find out.
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