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Old 07-09-2006, 07:29 PM
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Rebuilt SB running HOT

Hello once again. Thanks to everyone for your help in getting my motor started in regards to a previous thread.
I just got it started after a long rebuilding process. Its a 350 bored .040, 11:1 pistons, 6 inch rods, crower solid cam .484 I .504 E, RPM Air Gap Manifold, Holley 750 with vac sec.

This is my new problem; I have my temperture sensor mounted between cylinders 1 and 3 in the head, it gets HOT in that particular location as you know, the RPM air gap manifold mounts the thermostat and the carburetor above the intake manifold floor(for lack of a better name). The problem is that the temperture sensor is heating up "real quick" before the thermostat is even thinking about opening. In fact I am not even sure the thermostat is even opening in time before the block is already to hot.
This is what I did, after I got it started last night, I ran it for about 10 minutes, at that point this is what happened, the temperuture gage was reading about 200, and the radiator fluid/water was starting to come out in to the overflow tank, at that point I shut it down.
This morning I ran it on two separate occassions for about 5 minutes apeice. This give about 20 minutes of total run time, and I assume that is ok for initial break in, so I was going to change the oil/filter at this point.
ALSO, I pulled the thermostat out, boiled some water, and dropped it in to see if it was opening. It did in fact open. Unfortunately, I don't have the temperature reading on the stove to know exactly what temperature it did open, I probably cound have sprung for a thermometer. Anyway, I took the themostat back and got one rated at 180- 192 degrees. The one that I originally had in there was rated at 160 degrees. When I put the 180-192 degree themostat in, I started the motor and let it run at about 1500 RPM for about 5 minutes, I did this on 2 separate occanssions as I mentioned earlier. It still ran hot,

So, How can I get this beast cooled down considering my configuration?

Keep in mind the following, the radiator is just a two core piece of crap that I am only using for initial breakin, and I am not using a shroud yet. Provided I get a 4 core radiator, and a shroud, what else can I do to get the coolent in the motor before it gets to hot?

mouseman

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Old 07-09-2006, 07:45 PM
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might have some air in it----or-----as this did in fact happen to me

The water pump impeller came loose and was not pumping at all, Brand new pump too!

For a quick check---remove t-stat -- start motor--see if coolant is circulating thru radiator.


Bryan
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Old 07-09-2006, 08:03 PM
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You said =
the temperuture gage was reading about 200, and the radiator fluid/water was starting to come out in to the overflow tank, at that point I shut it down.
******************************


You shouldn't be puking at 200*.

Make sure that cap is actually holding at least 15 psi. Test it.
If you buy a new 16 psi cap, test it in the store. I bet you have to test at least 4 to get one that tests at least 15 psi.

Make sure your water pump is overdriven.

Needs more airflow.
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Old 07-09-2006, 08:10 PM
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Quote:
Originally Posted by mouseman
Hello once again. Thanks to everyone for your help in getting my motor started in regards to a previous thread.
I just got it started after a long rebuilding process. Its a 350 bored .040, 11:1 pistons, 6 inch rods, crower solid cam .484 I .504 E, RPM Air Gap Manifold, Holley 750 with vac sec.

This is my new problem; I have my temperture sensor mounted between cylinders 1 and 3 in the head, it gets HOT in that particular location as you know, the RPM air gap manifold mounts the thermostat and the carburetor above the intake manifold floor(for lack of a better name). The problem is that the temperture sensor is heating up "real quick" before the thermostat is even thinking about opening. In fact I am not even sure the thermostat is even opening in time before the block is already to hot.
This is what I did, after I got it started last night, I ran it for about 10 minutes, at that point this is what happened, the temperuture gage was reading about 200, and the radiator fluid/water was starting to come out in to the overflow tank, at that point I shut it down.
This morning I ran it on two separate occassions for about 5 minutes apeice. This give about 20 minutes of total run time, and I assume that is ok for initial break in, so I was going to change the oil/filter at this point.
ALSO, I pulled the thermostat out, boiled some water, and dropped it in to see if it was opening. It did in fact open. Unfortunately, I don't have the temperature reading on the stove to know exactly what temperature it did open, I probably cound have sprung for a thermometer. Anyway, I took the themostat back and got one rated at 180- 192 degrees. The one that I originally had in there was rated at 160 degrees. When I put the 180-192 degree themostat in, I started the motor and let it run at about 1500 RPM for about 5 minutes, I did this on 2 separate occanssions as I mentioned earlier. It still ran hot,

So, How can I get this beast cooled down considering my configuration?

Keep in mind the following, the radiator is just a two core piece of crap that I am only using for initial breakin, and I am not using a shroud yet. Provided I get a 4 core radiator, and a shroud, what else can I do to get the coolent in the motor before it gets to hot?

mouseman

Well for starters you need to make certain you are getting the engine full of coolant. You did fill the block via the water neck before you put the thermostat in, right?

Also, you should pull a heater hose while you fill it so you have a vent (just like a gas can).

Now stop trying to run it without a large enough radiator and a shroud. The more power you make, the more heat you generate, the better radiator you need. You also must have a shroud, it's a must. What about your fan? Do you have a clutch type fan, or a solid fan?
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Old 07-09-2006, 08:56 PM
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The radiator will puke if the system is full - that's normal.

Also, if you are using aftermarket heads with the small-type temp sensor, it is not compatible with the gauges in an older GM car - thae resistance values are way off.
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Old 07-09-2006, 09:08 PM
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A few things to do if all you want for now is to get some break-in time on the engine.

Install a good radiator cap to keep the coolant in the radiator.

Second, 200 is NOT hot, atleast not to me, especially on a new engine. I"d start worring if it got to 240.

Back it out of the garage and fire it up and run the garden hose slowly on the radiator fins. That should help a lot.

Get a bigger radiator and shroud for sure!
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Old 07-09-2006, 09:15 PM
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my car seemed to run at 200-220ish in peak summer heat, so i switched to a 3 row rad, added a litre of water wetter and now it wont see more than 200
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Old 07-09-2006, 10:37 PM
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I agree with Jmark. 200 deg isn't that hot. The electric fans on my Blazer arent even set to come on until 205. You must also remember that the thermostat only controls minimum engine temperature. Just like most everybody else has said you need to make sure the engine and radiator are completely full of coolant. Then start looking into whether or not you have adequate airflow through the radiator and make sure your radiator is sufficiently sized for your application... I bet if you put a shroud on it you'll drop your temps...
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Old 07-10-2006, 07:05 AM
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is the motor in the vehicle? make sure that the radiator's top outlet is above the level of the thermostat housing...
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Old 07-10-2006, 10:14 AM
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OK, now that I pulled my head out of my b...., I need a beating . I did not fill the block with water/antifreeze before putting my thermostat in. I just put the thermostat in filled the radiator up and started it. Damn, thats why the thermostat did not open because there was not any water in there, I hope I did not damage the motor. The first time I started it, I shut it off when it got to 200 degrees, that was in about 10 minutes then it crept up to about 210 220 at which point it started cooling down. The second and third time I started it, I did not run it more than 5 minutes for either time.

I have a flex fan (no clutch). The radiator cap is also going to be relaced(with correct psi). It is about at the same level as the thermostat in the intake manifold.

Ok, now that I know what I have to do, how do I do it? That is to say, when I remove the thermostat, how much water/antifreeze do I pour down into the thermostat hole in the intake manifold? I assume I top the radiator off after that?

Should I put the 160 degree thermostat back in, now that I know what the main problem is?

I have learned a very valuable lesson here.
Thanks for your help.
Time to go shopping for a good radiator, shroud, radiator cap,
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Old 07-10-2006, 10:29 AM
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I also forgot to mention that the water pump is brand new, and I saw the coolant moving around down inside the radiator when I removed the radiator cap.

How much smaller of a waterpump pulley should I get to overdrive my waterpump? The pulley on the waterpump now is standard size, but aluminum. The water pump is also standard long style.

The heads are iron 1.94 I, 1.5 E.

mouseman
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Old 07-10-2006, 10:42 AM
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Mouseman

Check the timing and make sure it's not running retarded. This will cause the engine to heat up and stay hot.

Joe
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Old 07-10-2006, 10:51 AM
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Dude, you don't have to fill the block with antifreeze prior to dropping in the thermostat.. You're supposed to fill the radiator up about half-3/4 of the way up, fire it, get it at the correct rpm speed for your break in, leave the cap off, and once the thermostat opens, it will begin purging the system of air which is when you start filling up the radiator slowly after the cap opens just to make sure there is no trapped air in your system. I seriously doubt you damaged your motor, when I blew my intake gasket a while back on the road, I had to drive all the way back home with coolant spewing everywhere. I only had about half of the radiator full by the time I got back home. Get a proper shroud on there before you drop tons of money on parts you might not need.
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