popping at idle

Discussion in 'Manton Push Rods Top Alcohol Tech Questions' started by Dean Boyd, Apr 6, 2018.

  1. Dean Boyd

    Dean Boyd New Member

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    Just wondering if I can get some other ideas on how to combat an idle problem I have with 2 different blown dragsters I help out with one is a basic blown BBC and the other is a psi equipped billet headed boss ford and both of the have a horrible popping sound after the burnout I thought I fixed the BBC when I raised the idle and the idle fuel pressure but it can back at the last meeting and with the ford the pop is tea bag if it runs less than 1.2gpm at idle we up it to 1.4gpm and it goes away but after the burnout it comes back in assuming that its got something to do with heat in the motor ????
     
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  2. Mike Canter

    Mike Canter Top Dragster

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    If it is popping out the exhaust then either unburned fuel is getting into the hot exhaust pipes an igniting or the timing is too far retarded. How is the oil contamination. Is it getting lots of alcohol in it after one run? What about idle egts? Where are they?
     
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  3. Dean Boyd

    Dean Boyd New Member

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    For the BBC when I upped the idle pressure I got less fuel contamination I do suspect that it maybe a bit retarded as the owner has lots of different timing marks and after only a few runs i have not been able to get a good read on the spark plugs as for the ford I think its way to retarded but the same owner does not want to advance it anymore the motor starts extremely easy like is had an starting retard function even my fail driver doesn't start ad easy as that motor
     
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  4. Dean Boyd

    Dean Boyd New Member

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    And no egt on the BBC and the ford the egt's are all over the place
     
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  5. Mike Canter

    Mike Canter Top Dragster

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    When I ran a Ford hemi a few years ago Carroll Carter said never to go beyond 26* advance on it. What is the timing set at on the Ford? when you say PSI equipped are you talking about the PSI screw or their roots blower? If it is a screw then does the BV gave the modified slot in the spool. What are the idle check valves set at on both motors?
     
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  6. Dean Boyd

    Dean Boyd New Member

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    From memory the timing is about 28 degrees the chambers have been modified by noon and to the same ad a brad 6 and yes its a screw psi blower and it does have the right spool in it I will have to ask the owner what the idle chev valves are set at what would be your recommendations for the check valves
     
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  7. Mike Canter

    Mike Canter Top Dragster

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    Normally idle return check valves are set between 8 1/2 to 10 lbs crack pressure.
     
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  8. Dean Boyd

    Dean Boyd New Member

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    Thanks the guy is racing tomorrow so I will get him to check them properly
     
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  9. Mike Canter

    Mike Canter Top Dragster

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    The Carrol Carter billet heads were very much like a Brad 6 head and 26* was max advance. It is possible with some ignition systems to have them retard when at idle. You should check and see what the ignition timing is at idle. Also see what the idle check valves are at and if what the barrel valves were set at on a leakdown.
     
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  10. Dean Boyd

    Dean Boyd New Member

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    Ok the owner says the idle check is about 12 lbs and the leak down is about 72%
     
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  11. Mike Canter

    Mike Canter Top Dragster

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    How much oil dilution on fresh oil after one run? During backup afterthe burnout what is the fuel pressure and fuel flow. How does that compare to the pressure and fuel flow at idle before the run?
     
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