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Thread: jet problem

  1. #1
    Senior Member MASTER BUILDER
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    jet problem

    My car is on alky,this summer it has been inconsistent with weather changes.I went from 157-160's to 160-164's this past weekend,it was fast the first pass in the heat but slowed down as the night went on. The mph was the fastest it has went,which means im going in the right direction but how can it slow down as the air got better?

  2. #2
    Senior Member RACING JUNKIE curtisreed's Avatar
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    If you are still lean when the air gets better it gets leaner-more lean however you want to say it. How much water temperature are you picking up on a pass? A little more info about the combination you are running and your fuel system will help the guys on her diagnose what might be happening.

    Curtis

  3. #3
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    383,6" rods,215 dart platinum iron eagle steel heads,555 solid lift,super victor,950 hp alky carb. Made 592 hp,525 tq. i ran these jets last year once it got hot out. I go in the water at 160* and its 175 on the return road after an 1/8th mile pass.

  4. #4
    Senior Member RACING JUNKIE curtisreed's Avatar
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    I usually try to shoot for 5-8 degree rise in temp in the 1/8. 15 is not to bad. Did it change this year since you say you ran these jets last year? What I'm getting at is could the fuel pump have changed on you. Don't know if it is electric or belt drive. Was there a fuel pressure change this year under power? If it were fuel pressure related jetting up will usually cause the problem to get worse on the big end because you can empty the bowls faster and the pump can't keep up, so I don't know that it is that just something to think about.

    By the way, looks like you have a very strong combination there. I have a 383, 11.3 compression, Track1s, .600-.640 282-290 106lsa with an older Rupert and I have .168" jets in it. I know it is not apples to apples but just a comparison. I gain right at 5 degrees with it in the 1/8.

  5. #5
    Senior Member MASTER BUILDER
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    the car was within a few thou. all day last year.Ive been looking at my log book and its been all over the place this year the jetting might have given it more power and made it worse.I put new slicks on at the beginning of the year and its been all over the place,also an alternator.I dont think its the alternator though because it carries over 14 volts at all times and i still charge between rounds.

  6. #6
    Senior Member RACING JUNKIE curtisreed's Avatar
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    I was thinking after my last reply if it were the pump you wouldn't be running more mph. Did you go to a different slick than you were using last year? I agree that it is not the alternator. The biggest difference I see is the change in slicks. How many runs do you have on them now? We had a new set we put on our dragster that took about 40 runs to settle in!! I will be breaking them in on my roadster from now on. I can do a better burnout on the for a couple of passes. Are your 60' times varying or everywhere on the track?

    curtis

  7. #7
    Senior Member MASTER BUILDER
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    Same tire 14.5 32 Goodyears only have 76 passes on them,seems like it varies 60 and 330 the most, mph is within 3 hundreths the whole day.

  8. #8
    Senior Member RACING JUNKIE
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    U maybe going the wrong way. One reason your car could be slowing down is that your a little rich and humidity usually increases at night. Alcohol doesnt like humidity. Eventhough its cooling down the rise in humidity will offset the temp. try this.. go back to 160-164s and put a 28 jet on your high speed air bleed, you probably have around a 35 now, the high speed air bleeds are the ones next to your vents your carb. This will keep your engine alittle leaner out the gate for horsepower, which will keep your chassis planted and the smaller air bleeds will make your big end richer letting you keep your MPH.


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