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Thread: sbc cooling problem...

  1. #1
    Member MASTER JOURNEYMAN
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    sbc cooling problem...

    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.

  2. #2
    Senior Member RACING JUNKIE
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    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
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  3. #3
    Member MASTER JOURNEYMAN
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    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.

  4. #4
    Member MASTER JOURNEYMAN
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    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.

  5. #5
    Senior Member MASTER BUILDER
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    overheating

    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

  6. #6
    Member MASTER JOURNEYMAN
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    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.

  7. #7
    Senior Member MASTER BUILDER
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    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

  8. #8
    Senior Member RACING JUNKIE TheYellaBrick's Avatar
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    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/pontiac...Readplugs.html
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  9. #9
    Senior Member DYNO OPERATOR bixblk's Avatar
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    Thanks DD

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

  10. #10
    Senior Member EXPERT BUILDER
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    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.


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