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Thread: car slowing down

  1. #1

    car slowing down

    I have a 377 small block with 13:2:1 pistons, dart heads 208 valves, cam 630 lift 106 lobe sep, and a quick fuel 750 carb. i just built the car and tonight was the third night it has been run. when i first took it out it ran a 6.49 at 106. the timming was set at 18 deg. the pump was to small and was running the bowls dry and running lean. since then i put a big pump on it and cured the prob. now i took it back and with the same settings it ran a 6.72 in an 8th mile at 101 mph. i turned the timing up to 30deg adv, and went bigger jets in the carb. its richer but burning good on the spark plug. nopw the car slowed down to a 6.98 at 99mph. now the fuel pressure is at 6lbs at the reg. the cam is from 3400 to 6800 and i am switching gear at 6400. it has a 5000 stall on a 2 speed can some one help me on why when the car was starving for gas it was faster then now when its all right its slower

  2. #2
    Senior Member EXPERT BUILDER
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    I guess it could have hurt something being that lean, have you done a compression check? or a leakdown? If that goes well then,
    I think I'd jet it down and make a run, jet it down make a run ect..Until it quits picking up, Then do the timing same way. Must be way fat, or something going wrong with a bearing or something...
    When was the first run made and the last? Don't forget to figure in the weather it usually slows me around a tenth-a tenth and a half.

  3. #3
    Senior Member RACING JUNKIE
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    Re: car slowing down

    Quote Originally Posted by fastballcurt
    I have a 377 small block with 13:2:1 pistons, dart heads 208 valves, cam 630 lift 106 lobe sep, and a quick fuel 750 carb. i just built the car and tonight was the third night it has been run. when i first took it out it ran a 6.49 at 106. the timming was set at 18 deg. the pump was to small and was running the bowls dry and running lean. since then i put a big pump on it and cured the prob. now i took it back and with the same settings it ran a 6.72 in an 8th mile at 101 mph. i turned the timing up to 30deg adv, and went bigger jets in the carb. its richer but burning good on the spark plug. nopw the car slowed down to a 6.98 at 99mph. now the fuel pressure is at 6lbs at the reg. the cam is from 3400 to 6800 and i am switching gear at 6400. it has a 5000 stall on a 2 speed can some one help me on why when the car was starving for gas it was faster then now when its all right its slower
    I hope the mechanical advance is locked out.
    -WJ Birmingham

    OneBadGMC.com

  4. #4
    Senior Member MASTER BUILDER
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    If your Dart heads are 23 deg set the timing at 36 deg and put the stock jets back in the carb.most universal carbs are rich by one or two sizes. running your timing retarded as much as you have will definitely affect plug color. as was said in another post,make sure your dist is locked.Bill
    Hendrens Racing Engines
    1310 U.S. Hwy 221 North
    Rutherfordton N.C. 28139
    828-286-0780 Bill, Steve, Mike
    www.hendrensracingengines.com

  5. #5
    Senior Member RACING JUNKIE
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    Not trying to hijack this post,bit my dist is not locked out.It is mechanical only and all comes in by 2500.I leave at 3000+.Should I lock it?Just figured it would start easier with less timing????BTW.36 degree timing sounds like a good place to start.If you're mph is falling off as well as et,that is indication of hp loss moreso than just et.What size jets were/are you running?Powervalves?Good luck
    "The problem with quotes on the Internet is that you cannot confirm their validity"- Abraham Lincoln

  6. #6
    Senior Member EXPERT BUILDER
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    did you check your throttle linkage? I've fixed several i don't know why my car slowed down problems that way .OLDS48 don't lock your timing down save your starter & flywheel.

  7. #7
    Senior Member RACING JUNKIE
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    I always thought like olds48 in that I figured as long as it was in by my launch rpm I was good and it would start easier. I now lock it out instead just because it is easier to set the timing. My car lives lives in a housing addition...The neighbors just L O V E the open headers .... with it locked I just put the motor at 38 deg before tdc and drop in distributer and make sure the cap is indexed correctly. I still put a light on it to check but I don't have to rev it up and make all kinds of racket to do it. Mine starts just fine with it at 38 deg. I have 1 battery in the trunk and a CSI mini starter( now they are CSR)


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