Idle Surge In Gear

Discussion in 'Manton Push Rods Top Alcohol Tech Questions' started by BEDNAR1320, Mar 13, 2017.

  1. Witchdoctor

    Witchdoctor Member

    Joined:
    Jan 5, 2005
    Messages:
    214
    Likes Received:
    0
    Having the same problem. Surges so bad its hard to get it in gear. Idles (but surges bad) at 2200-2400 but then its harder to stop the car after burnout or backing up. Brake pressures are good.

    Pro mod, Bruno, Neil Chance convertor, Lenco 3 speed.

    526 BAE Hemi, CFH heads, Kobelco HH 29%, Rage 18 GPH pump, Mag 44 at 28*. Pump PSI is about 45# @ 2200RPM port nozzle is "0" so I don't think they are leaking at idle. Idle check is 8#, BV leak is 80%. Port check pressure opens at 8# with a stiff spring. JBR 4 blade injector is .012 all the way around the blades. EGT are all around 4-500* with the exception of cyl 1 (6-700ish) and cyl 4 is (4-500ish) Flow meter shows less than 1 at idle. We have an adjustable air valve on the BV as well as have pulled lean out plugs in the hat. Turn the air vale all the way open and pull a 5/16 plug and it cleans up very very slightly. I would assume the change should be drastic with such big openings.

    We have had idle check PSI everywhere from 4 to 12 PSI without much difference. BV from 84-76% without much difference. Changed hat nozzles to ones with out air bleeds (saw no difference) also reduced the hat nozzle area down some. (saw no difference). Changed timing to 30 and it cleans up and idles better. (they tell me 30* is to high to be safe.)

    When you push the trans brake button to stop the trans the surge gets really bad, let off it goes back to just bad. We have an MSD grid that we have retarded the timing at launch- release of the button, and also set it up with no retard. Engine still surges really bad when button is on, bad when its off weather we retard the timing or not.

    Breather tubes on valve covers are open.

    We are trying to get it to idle at 2200 ish with no surge and 28* timing.

    WHAT THE HELL ARE WE MISSING... Damn this is frustrating. Thanks for any advice.
     
    #21
  2. jay70cuda

    jay70cuda Member

    Joined:
    Sep 30, 2009
    Messages:
    920
    Likes Received:
    13
    Wow 28? Hope you have like 10-1 compression. And 2200 idle with 1.0 fuel flow seems lean. With that amount of timing and fuel says a very lean condition to me. Have you tried 25 degrees and then see what happens. Or warm it up and pull the valve cover breather tunes off while it's on the brake in the pits? I was on the dyno and the tubes were open or so we thought. Pulled the tubes off and whalla , beautiful idle !! Same exact thing your describing to me now
     
    #22
  3. td3829mk

    td3829mk Member

    Joined:
    Dec 31, 2015
    Messages:
    115
    Likes Received:
    6
    Lean. Seal the hat and if you're using a spacer be sure to seal it good as well. Mine was surging bad even after setting blade gap, BV, etc. New gasket between hat and spacer and new o ring between blower and spacer cleaned it up. Idles smooth as glass right around 1700. Also try dropping your timing down to 26* and see what it does.
     
    #23
  4. Mike Canter

    Mike Canter Top Dragster

    Joined:
    Mar 10, 2004
    Messages:
    4,098
    Likes Received:
    65
    If still a problem then set the idle return poppet to a crack pressure of 8 1/2 to 9 1/2 lbs crack pressure then set the BV leak down to 82-83 with the outlet line totally off and a -6 cap on the idle return poppet.
     
    #24
  5. Witchdoctor

    Witchdoctor Member

    Joined:
    Jan 5, 2005
    Messages:
    214
    Likes Received:
    0
    Jay-Compression is about 11:1. Breather tubes are off when we are doing this- on Pro Jacks.

    TD- We have resealed everything- o-ring and silicone on everything. Even sealed up the front of the injector where the aluminum frame for the butterflies is attached to the injector. We have had timing from 18* to 30*. As expected at 18 its so fat, lazy it barely wants to run.

    Mike- We have tried exactly that when setting up the barrel valve. Even thought maybe the spool was modified so I bought a brand new BV and nothing changed.

    Some more things I thought about:
    1-It uses fuel like crazy at idle- to me that's rich??

    2-Could it be leaking (sucking air) in the lifter valley? The intake not sealing to the heads type problem? I would think when we cracked the throttle we would see smoke out the pipes because it sucked oil??

    3-The Racepak pan pressure sensor is located in the intake oil cap, where you would pour oil in the back where a traditional distributor would go. Its reading 0.1 or 0.2. I don't know what normal is because we have never used one. If it was sucking air through the intake/ heads wouldn't the vacuum be higher on the sensor?? Is there a such thing as normal vacuum / pressure at idle?

    4- On regular engines you can spray carb clean or use propane to check for vacuum leaks-idle raises up when you hit the leak. How could we do it on this?
     
    #25
    Last edited: May 27, 2017
  6. Fuel Cars

    Fuel Cars AA/AM

    Joined:
    Aug 20, 2003
    Messages:
    283
    Likes Received:
    2
    Have you checked the cam timing and for a bent or broken valve?
     
    #26
  7. Witchdoctor

    Witchdoctor Member

    Joined:
    Jan 5, 2005
    Messages:
    214
    Likes Received:
    0
    We have not
     
    #27
  8. td3829mk

    td3829mk Member

    Joined:
    Dec 31, 2015
    Messages:
    115
    Likes Received:
    6
    Might sound silly but silicon didn't work for me in regards to hat/spacer sealing. I found a nice gasket from RBS that worked great and the surging stopped. You may want to give that a shot? Also maybe try simplifying your fuel system setup. More poppets more problems. Just my .02
     
    #28
  9. Witchdoctor

    Witchdoctor Member

    Joined:
    Jan 5, 2005
    Messages:
    214
    Likes Received:
    0
    I'll look into the gasket. We have capped off the ports and just tried it on the hat and same surge.

    We just tried starting the car and measuring PSI at the dist block for the hat nozzles and get -5 or -6. Is that right? Shouldn't it have pressure? also switched the sensor out and the same thing with a new sensor.

    However with no other changes the pump pressure measured at the pump is now 35# at 2200 rpm. We have not changed anything else and it was 45-50# yesterday. WTF!
     
    #29
  10. td3829mk

    td3829mk Member

    Joined:
    Dec 31, 2015
    Messages:
    115
    Likes Received:
    6
    Is the oil saturated more than normal? Have you checked your pump seals? Might be leaking where your extension is. Would explain the fuel being used at idle, the drop in pressure and the lean-rich-lean-rich condition causing the surge. That pressure at the block doesn't seem right either
     
    #30
  11. Witchdoctor

    Witchdoctor Member

    Joined:
    Jan 5, 2005
    Messages:
    214
    Likes Received:
    0
    The oil really isn't to bad. The pump was sent to Rage and was checked out as good.

    What should the pressures be? I know you cant say exactly but whats a normal range on a Racepak?

    Pump pressure measured at the pump?
    Pressure after the BV measured at the hat dist block?
    Flow at idle?
    Pan pressure at idle? Can it be negative (vacuum)?
     
    #31
  12. Mike Canter

    Mike Canter Top Dragster

    Joined:
    Mar 10, 2004
    Messages:
    4,098
    Likes Received:
    65
    Try bring the BV down to 80% and see what happens.
     
    #32
  13. Witchdoctor

    Witchdoctor Member

    Joined:
    Jan 5, 2005
    Messages:
    214
    Likes Received:
    0
    We have gone clear down to 76% with no luck.
     
    #33
  14. kosky racing

    kosky racing Comp Eliminator

    Joined:
    May 11, 2003
    Messages:
    599
    Likes Received:
    20
    The idle ck. could be worn - how old is it?
     
    #34
  15. Witchdoctor

    Witchdoctor Member

    Joined:
    Jan 5, 2005
    Messages:
    214
    Likes Received:
    0
    We put a new one in and even switched it with the pump saver one to make sure.
     
    #35
  16. kosky racing

    kosky racing Comp Eliminator

    Joined:
    May 11, 2003
    Messages:
    599
    Likes Received:
    20
    that wont work----
     
    #36
  17. Sandracer695

    Sandracer695 Member

    Joined:
    Jan 8, 2005
    Messages:
    227
    Likes Received:
    1
    Who's blower? I had a customer buy a used Littlefield blower. LB20. I could not get the motor to stop surging. Found out previous owner of blower changed the rear bearing plate for one that was machined out for a standard rotor instead of non machined hi helix rear bearing plate. Littlefield told us what to look for. Changed rear bearing plate and surging went away. Just a thought.
     
    #37
  18. Witchdoctor

    Witchdoctor Member

    Joined:
    Jan 5, 2005
    Messages:
    214
    Likes Received:
    0
    Its a Kobelco that we had dynoed at SSI. They said everything was good but it something we can check into.
     
    #38
  19. Will Hanna

    Will Hanna We put the 'inside' in Top Alcohol
    Staff Member

    Joined:
    May 6, 2003
    Messages:
    6,365
    Likes Received:
    61
    In an earlier post I mentioned I had a similar experience with a customer's pro mod and roots. I about pulled my hair out. All of the "traditional" fixes had zero effect. I leaned the barrel valve all the way down to .5 gallon at idle (just to see what it did to the surge, would never run it that lean - nice thing about having a dash.) Like you said, did it with or without timing, on and off the brake. More air, less air, didn't make a damn.

    Have you tried a different or lighter idle return spring? My customer had a really strong return spring on the right side (was trying to crutch a cheap throttle cable). Went to a lighter return spring and it purred like a kitten. The spring was strong enough it would get into a cycle of flexing the throttle shaft causing the surge.

    I would go back and look at the simple stuff. Words to live by that Tom Conway taught me is "these things aren't that smart."

    If it's sucking air, it's going to be on top of the blower. Even at idle, there is enough pressure in the intake that it's not going to suck air if it had a leak on bottom. My thoughts on a leak causing the surge is that the leak would cause a high idle condition that you would have to chase on the linkage/air opening to bring it back down, leading to too tight of blades.

    I have seen some BBC's have the intake get loose and suck oil through the ports on the big end, but that is because there is a split second of vacuum and the oil in the lifter valley gets sucked in. If it had enough of a leak it would huff pretty good out of the breather tubes.

    I have heard on rare occasions some rear plate mods (supercharger) not working with converter cars.

    When you get your idle fixed, most converter cars are much happier with a 1900-2000 idle in neutral. hits the reverser pretty hard the higher the idle.
     
    #39
  20. Will Hanna

    Will Hanna We put the 'inside' in Top Alcohol
    Staff Member

    Joined:
    May 6, 2003
    Messages:
    6,365
    Likes Received:
    61
    If you try throttle spring, unhook the throttle cable just to eliminate another variable. Maybe the throttle cable is too short or not adjusted just right and jamming the blades closed
     
    #40

Share This Page