sbc cooling problem...

[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 hot.....it 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....no 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.

[fast75vega]

between my brother and brother-inlaw and mine.... we have 3 vega's..... :)

i was the only one that was running hot and tried the same stuff you did!! it turned out to be under jetted by quite a bit... even thought the motor pulled the whole way down and the "plugs" never showed any sign of being lean. i was running 200 to 220ish at the end of the track.... so i started jetting it this weekend and it not only got faster though the traps but my 60' footers dropped and my temps were 180 thought the traps now :)

[lodilobo]

That's definitely worth a shot....just like you, the plugs have never looked so good....seem to be burning very well. I'm using 96's in a 1090 dominator. I'll bump up to 97's or 98's and give it a try. Thanks.

[lodilobo]

Thinking about it, that makes a lot of sense. Of course running too lean will make the motor run hot, but also, my '60 ft. times have been not what I was expecting, and my mph has been around 142....less than I would expect with the car weighing in at 2500# with me in it, and the hp anywhere near what the dyno said. What really kind of through me off that trail, is that early in the year, I moved up to bigger jets, and my mph dropped. But that was before I had the timing dialed in, so I'm sure you're right about this. Thank God for fellow Vega owners.

[chevyart]

hey ladi look at my posts under sbc hardblocked and overheating... my plugs were burning white on the porcelain.. was way underjetted. went up quite a bit in jet size and it ran cooler, and the porcelain is just turning brown. this week, bigger jets and i presume lower temps(along with a few other changes) read my posts and you will see what i have been going through. good luck art

[lodilobo]

Art....I read your posts and the replies...these over heating issues are annoying, aren't they? The thing that puzzles me, with the jetting, is that my plugs looked like they were burning really well....never had white electrodes. A lot of people say it's almost impossible to judge plugs if you're using msd ignition, which I am. I have already bumped my jets up from 96's to 100's. That should tell me something. I can't test it until Friday test / tune.

[chevyart]

hey lodu ill be watching for your posts to see if there were any performance results(or overheating results) after you go out next time. good luck art

[TheYellaBrick]

The plugs are going to read different with unleaded 10% than in the old days on leaded pure pump gas.

NOTE! You do NOT read the porcelain for Jetting !


"Ground Strap" = Heat Range
"Plug's Base Ring" = Jetting
"Porcelain" = signs of pre-ignition/detonation

EXCELLENT article;

http://www.angelfire.com/fl4/pontiacdude428/Readplugs.html

[bixblk]

DD
Thanks,, great article (link) about reading plugs
Jeff M

[wazup]

DD your correct, if you are use racing fuel tho you should be able to make a pass and shut it off and pull the plugs and get a reading if you know what to look for. Race fuels have dye in them. I use a magnifier to read my plugs on every pass because of nitrous.

[chevyart]

DD thanks for info on reading plugs. i learn something new every day on tuning these engines. art

[TheYellaBrick]

Agreed on racing fuel. It needs to be an under power clean shut off to get a proper reading.

[TheEngineer]

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.



http://s3.amazonaws.com/s3.racingjunk.com/ui/9/02/28243029-855.jpg

http://s3.amazonaws.com/s3.racingjunk.com/ui/6/02/28243026-864.jpg

[roadkill2]

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 hot.....it 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....no 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 . .