BBC Idle Temps

Discussion in 'PSI Superchargers Tech Questions' started by Critical Mass, Oct 15, 2013.

  1. Critical Mass

    Critical Mass Member

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    I am trying to reduce my #3 and #8 high idle temps in my blown alky 548 BBC, PE drag boat motor. They are running around 700 deg. The motor has 11.4 comp, Littlefield 14-71 roots, buzzard hat and K-valve on an indy manifold, using a 44 mag.

    I have tried two methods:
    #1 Set the butters to .012 with the BV set at ~80% leak down and;
    #2 Set the butters to .005 with two air vents open on the hat with about the same leak down.

    The idle is ~1800 rpm for both methods. With the butters set at .012 and no air vents open I was blowing fuel out the pipes. I want to use air vent method because it doesn't milk the oil as much at warm up. Temps down the track all look good around 1050 deg.

    Any ideas how I can reduce #3 and #8 temps. or should I ignore them since my temps down the track look good.

    Thanks in advance for any advice, Joe
     
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  2. Wildcatracing

    Wildcatracing Member

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    ignore them as theres no easy way to change them individually and it very quickly becomes irrelevent if they even out on the run
     
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  3. Mike Canter

    Mike Canter Top Dragster
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    Those uneven idle temps are caused by the manifold design and not much you can do about. As you said the temps are good during the run so I would not worry about it. If you don't want your oil to be so milky at idle with .012" then adjust your barrel valve by a couple of percent at a time until it is no longer milky. You should adjust the BV until you get a responsive off idle feel the check and see where the leakdown is and make a note of it so you can get there again.
     
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  4. Critical Mass

    Critical Mass Member

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    Thanks Guys for the info.

    I am going back to the .012 butter clearance in the hat and lean out the BV a little. I now need to look at my egt's from going from idle to full throttle for a smooth transition; right now I'm getting about a 75 deg drop in temp from #8 when the ports open.

    Also, I've looked at the data with two of the hat vents open and it shows a romp-romp-romp rpm idle pattern which people have told me is hard on the rods and crank. It is hard for me to believe that would be an issue at 1800 rpm?

    Thanks again, Joe
     
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