Hot 350 or not

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Re: Hot 350 or not

Postby 283vega » Sun Jun 02, 2013 5:37 am

You said your car cools down at freeway speeds better with the electric fan off? I think you need to rig a spoiler or somthing to cut off air flow from under the car and force it through the radiator.
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70 corvette


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Re: Hot 350 or not

Postby pcguy » Sun Jun 02, 2013 9:55 am

Sorry about that - the written word and all - here's what I edited the guilty text to be.

"The electric fan helps, when I turn the engine off I can get the temp back to 200 or less in a very short time if I leave the fan running."
2009 Corvette ZR1 - bone stock
1975 Vega Hatch - Built 350/TH350/3000 Stall - 400ish HP
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Re: Hot 350 or not

Postby pcguy » Sun Jun 02, 2013 1:58 pm

About to remove the radiator for the 4th time in 8 months. Have done some more searching and found the following considerations:
1. A radiator first needs to be able to pass about 50+ gpm of coolant for a SBC.
2. Then it needs to be clean enough on the outside in order to effectively transfer the heat.

If either of those two are not true, especially No. 1, there will be heating problems directly related to the radiator.

This radiator is obviously older and while it appears to my untrained eye to be in good shape, I have nothing empirical to determine how it is functioning.

I did find a very basic test that goes like this:
With the radiator out of the car and fully drained, lay it on level ground and fill it from a 5 gallon bucket using a funnel and being careful not to spill much. When it’s full, do the math to determine how many gallons are in the radiator. Then lift it up so that it can drain fully, kind of like cocked with the outlet at the low point, and check the number of seconds it takes to drain. This is a gravity test so it really won’t tell you how much coolant it will pass under pressure from the water pump. But, it will give you some idea as to how clogged the tubes may be.

What I read elsewhere was that a 1.5 gallon radiator should empty completely in 4 seconds – that equals about 22+ gpm.

Also, I found another test that indicates a problem if there is backpressure forming in the radiator at speed. Watching the temp gauge, you will notice that the temp drops a bit just as the thermostat opens. When that happens, check the firmness of the radiator inlet hose at 2500 – 3000 rpm – that hose should be fairly easy to squeeze at that temp and should not immediately firm up at a higher rpm.

This hose failed that test and the firmness fluctuated with the rpm.

Let me know if you have any thoughts in this regard – BEFORE I REMOVE THE RADIATOR again. LOL
2009 Corvette ZR1 - bone stock
1975 Vega Hatch - Built 350/TH350/3000 Stall - 400ish HP
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Re: Hot 350 or not

Postby pcguy » Tue Jun 18, 2013 10:47 am

Well, I've been through this way too many times and I began to wonder if it's something more obvious. Unfortunately, I'm not able to easily test any changes since I live on the coast and it never gets hot here - 60 mile round trip on a hot day inland to determine what effects, if any, a given change will have.

After completely boiling out the radiator (lots of stuff came out) and reverse flushing with a hi volume of water (trapping the output for inspection), there is zero change - well, maybe a couple of degrees better at 215. This setup should run at under 200 at all ambient temps.

So I was looking to see if the under hood temps (thin wall headers, small compartment, etc) could be the contributing factor - looking at hood louvers. The trans cooler was/is mounted on the flat under the radiator and was/am considering removing the grill and mounting it up front and off to the passenger side as much as possible.

Well, in trying to figure out what the proper steps would be, I noticed that the front license plate hung down fully below the bumper and right in front of the central part of the radiator. It also extended toward the front of the engine right up to the main pulley.

Does it make sense to you guys that at 65 MPH that plate location would cause enough turbulence to keep the system from cooling properly? I’m going to remove it and move the trans cooler, but I’m wondering if, in the meantime, I should continue my search for the right hood louvers.
2009 Corvette ZR1 - bone stock
1975 Vega Hatch - Built 350/TH350/3000 Stall - 400ish HP
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