sbc cooling problem...

Old 09-04-2012, 04:24 PM
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Default reading plugs

DD thanks for info on reading plugs. i learn something new every day on tuning these engines. art
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Old 09-04-2012, 04:37 PM
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Agreed on racing fuel. It needs to be an under power clean shut off to get a proper reading.
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Old 10-29-2012, 07:40 AM
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This will help with the cooling issue to some extent. Add these cooling lines from the back of the intake (rear head water jacket ports) to the filler neck outlet.

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Old 10-31-2012, 08:22 AM
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Default Re: sbc cooling problem...

Originally Posted by lodilobo
I have a '71 Vega with a 439 c.i. 18 degree motor, which dyno'd at 755 h.p. It has 14.7 :1 compression and is a low 9 second race car. The motor is a new build this year, and due to limited room in front of the engine, because of the necessity for a vacuum pump, I had to go with an electric water pump. I had always used an Edelbrock mechanical pump before the new motor. In the past, the car always stayed around 175 - 180 degrees. The car now runs extremely gets to 210 - 220 after 3 passes, and takes forever to cool down. Here are the different things I've tried to correct this problem...180 thermostat....160 thermostat...restrictor in place of a thermostat....changed from CSR pump to Mezziere. Yesterday, I did a pressure test on the cooling system, to see if there might be a blown head gasket, even though there are no other indicators of it. It held at 15 lbs. for over 5 minutes, so I'm pretty sure the heads / gaskets are not the problem. The only other thing I can come up with is the radiator. It is a new aluminum unit, that I bought form a vendor on RJ, and it measures 27"w x 17" h x 3" thick.....2" shorter than my old radiator. Once again, I needed the clearance after relocation. I'm considering removing the new radiator, and going back to the old one, but it will not be an easy swap, so I don't really want to do that. Anyone with ideas on why this motor runs so hot, please reply. I must be missing something here, but can't come up with it. I forgot to mention earlier....the electric fan is mounted in front of the radiator, and is wired correctly to pull air through toward the engine.
OK, start with the root of the problem.

After a pass, with the water pump running on the way back to the pits.

What is the actual temperature of the thermostat housing and the inlet side of the Radiator? (Should be about 10 over your installed thermostat)

What is the actual temperature of the bottom of the radiator at the discharge outlet? (Should be right around 140)

Without that information, I might as well be answering the question; "How Much is My House worth?", although you've never seen it.

Just a SWAG here, but my first guess is that your radiator is passing too much water too fast to allow heat exchange to take place. Which is one of the two things you touched on at the beginning. You changed the Radiator and you changed the Pump. You sped up your water flow and you cut the volume of heat exchanger. That, by itself will raise the temperature and it also becomes a "Cumulative" Problem if you're not cooling it adequately between passes.

The "fan in front" is a problem, because, as often as not, you aren't running it when you make a pass and they generally "Block" air just about as good as they do when they're turned on and trying to work. And in a 9 second car, at 140 mph, even if they're turning, they may be creating a better door than a window. It takes a really high volume fan(s) to equal all the air flowing through a radiator at that speed . . Unless of course, you have the front end blocked off for streamlining.

You didn't say how much time you're spending between passes so that's another unknown, but if you're running low 9's I'm guessing 15-20 minutes. If you keep the pump running in the pits does it bring it down?

Lean mixture could be the problem but if it's lean enough to cause this kind of heat it should be shooting ducks at the shift and in the lights . . And your plugs ought to be blue up the threads about two and a half-three "Rings" . . (That's how I look for heat in a plug, but wotthehelldoIknow?)

I think it's cooling system gremlins, and they're simple to fix, but a bitch to sort out . .
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