popping the bust plate and breaking belts?

Discussion in 'Manton Push Rods Top Alcohol Tech Questions' started by sune, Jun 3, 2013.

  1. TADHemiracer

    TADHemiracer Member

    Joined:
    Dec 9, 2010
    Messages:
    346
    Likes Received:
    13
    Fuel Cut-off vibrating closed

    I had the same thing happen several times before I figured it out, too. I added an overcenter spring to hold the fuel cut-off open during the run but could still manually close the valve with the lever. No more problems with vibrating the valve closed or leaning out and blowing the burst panel, at least not for THAT reason.
     
    #21
  2. TADHemiracer

    TADHemiracer Member

    Joined:
    Dec 9, 2010
    Messages:
    346
    Likes Received:
    13
    Possible Lean Out Conditions

    True enough, unless there is a piece of grit floating/rolling around inside ONE nozzle that might cause ONE cylinder to instantly go lean. I could imagine a backfire under those conditions that would not show up on a plug reading. Very remote chance, I know, but still something worth checking out. Pull the nozzle lines and LOOK in the nozzle with a light and maybe even a magnifying glass if you are old and gray like me.
     
    #22
  3. Mike Canter

    Mike Canter Top Dragster

    Joined:
    Mar 10, 2004
    Messages:
    4,084
    Likes Received:
    64
    All that you guys are talking about is good but if it went lean because of a collapsed hose, or a piece of dirt in the fuel system, or the vent not big enough on the tank, or the fuel shutoff closing all would result in a lean indication on one or more plugs or the loss of a ground strap or a smashed upper rod bearing. You can't go lean without your plugs knowing it.
     
    #23
  4. sune

    sune Member

    Joined:
    Jun 20, 2009
    Messages:
    141
    Likes Received:
    0
    Fuel managment: i only run one high speed -6 poppet with a pill in it. (I went 5 numbers down on the pill and put 2 shims in the poppet. after the first run. We also changed the fuel pump to a fresh one (same size of course, enderle 1200). No change, it still broke the belt and popped the panel).

    Fuel shutoff: i have the overcenter bracket and spring

    Fuel Tank: It is baffled, mounted in front of the engine. I have never run the tank dry it is quite big. It has a -8 vent on it (one 90 degees hose end and 20 inches of -8 hose). The main feed line going to the pump is a -12 about 5" long, it exits the tank at the bottom and has a small sump. All the returns enters the tank at the top. Fuel tank is holds about 45 liters

    I got the engine apart now everything looks good. Going to check all the lines and poppets today.

    I ordered a new set of wires and some tighter valve springs. next time out i'll put more fuel in it and see what happens. It is odd tho according to the tuneup it should be very rich as it is now. I can't really think of anything else to try. As i have not found any errors.
     
    #24
    Last edited: Jun 5, 2013
  5. altered8

    altered8 Member

    Joined:
    Mar 9, 2005
    Messages:
    58
    Likes Received:
    1
    vent too small

    i would do the glug test as Will explained. Your vent should be able to replace the same volume as your pump supply but a -8 vent is too small for a -12 supply
     
    #25
  6. sune

    sune Member

    Joined:
    Jun 20, 2009
    Messages:
    141
    Likes Received:
    0
    I just now tried the glug test.

    With all returns capped and the tank lid on and closed it drained without a single brup or glug.
     
    #26
  7. rb0804

    rb0804 Member

    Joined:
    Aug 7, 2010
    Messages:
    453
    Likes Received:
    12
    Bearings

    What do your bearings look like after this happens?
     
    #27
  8. sune

    sune Member

    Joined:
    Jun 20, 2009
    Messages:
    141
    Likes Received:
    0
    bearings

    @ rb0804

    All bearings are perfect, just done checking them.
     
    #28
  9. Comax Racing

    Comax Racing Member

    Joined:
    Sep 20, 2006
    Messages:
    669
    Likes Received:
    6
    First of all I'm no expert at all on this but I believe a #8 vent is fine for a # 12 inlet. I use a #10 on a 1 1/4" inlet and it passes the "glug" test no problem. Isn't a #12 inlet a little small for the engine he is running? Is this maybe the issue? Don't most us a 1" or larger inlet?

    Corey
     
    #29
  10. Will Hanna

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

    Joined:
    May 6, 2003
    Messages:
    6,350
    Likes Received:
    56
    inlet hose

    Are you running a standard AN hose from the tank to the pump? You need a reinforced hose for this, or the pump will try to collapse the hose. I'm not saying that is THE problem, but it could be A problem.

    Since you have a power grid, why don't you download the run info off the sd chip and at least see what rpm it is happening at, look at the timing and other things the grid is doing to make sure it's all doing what you are programming it to do.

    Are you sure you are going wide open throttle? If you are going part throttle, you are creating a lean situation because the barrel valve spool is not full open.

    How hot does it get at idle? Do you have any kind of head temp gauge?
     
    #30
  11. sune

    sune Member

    Joined:
    Jun 20, 2009
    Messages:
    141
    Likes Received:
    0
    @ Will

    The hose is only 5 inches long. I don't know the brand or make of it, But I can't squeeze it enough to flatten it, even when using both hands (don't know if that is worth anything).

    I'll check the sd card on the grid.

    I believe it was wide open.

    No head temp gauge, it takes quite awhile to warm up at idle.
     
    #31
    Last edited: Jun 5, 2013
  12. sune

    sune Member

    Joined:
    Jun 20, 2009
    Messages:
    141
    Likes Received:
    0
    Just checked the sd card in the powergrid.

    It didn't save the runs as i didn't launch using the transbreak which is setup to start the recording. It did save the data from the warmup in the pits where we tested the transbreak.
     
    #32
  13. Micetich

    Micetich New Member

    Joined:
    Oct 5, 2006
    Messages:
    74
    Likes Received:
    0
    burst plate popping

    Britt said back in the IHRA days running straight rotors the blower would do this if set too tight on end clearance. It is probably not your problem if it happens at the same point every time but worth checking. If end clearance is too tight the rotors will touch the end plates when they bow up from boost. Look at endplates for grooves or wear usually at the top near the tip. Touching will spark or heat up ignite the fuel in the blower. Breaks belt and pops panel. Motor bearings and plugs look like new. Had it happen a couple times before he figured it out. Also motor can be lean at some point and not show on plugs or bearings. Only have to be off one cycle to pop the burst panel, plug does not show everything, it is more of an accumulation over time.
     
    #33
  14. blown375

    blown375 New Member

    Joined:
    Sep 9, 2005
    Messages:
    733
    Likes Received:
    0
    Any chance it could be valve springs ?
     
    #34
  15. craig moss

    craig moss Member

    Joined:
    Sep 29, 2006
    Messages:
    572
    Likes Received:
    5
    How tight are the valve guides ??
     
    #35
  16. bryanbrown

    bryanbrown Member

    Joined:
    Dec 21, 2003
    Messages:
    323
    Likes Received:
    0
    Have you made a run without the grid? If it was me, I'd make a run on straight mag and see what it did. If it worked then a run on the crank trigger. Why do you need the grid if you're not moving the timing
     
    #36
  17. sune

    sune Member

    Joined:
    Jun 20, 2009
    Messages:
    141
    Likes Received:
    0
    Valve springs: they are between 310 and 340. But i ordered a new set, just to be sure

    Valve guides: I don't have the numbers on them but they are i descent shape. (half a season old)

    Powergrid: At he moment i am not using any features from it, but the rev limiters. But i plan to in the future. But yes next time out i'll have to do a run without it just to test if that is messing with anything.
     
    #37
  18. Matt

    Matt Member

    Joined:
    Jun 25, 2006
    Messages:
    99
    Likes Received:
    0
    This is way out left field but have seen this before, have any of the spark plug holes in the head been re-threaded with a steel heli-coil, motor kept putting the panel out after half track, it was the end of the heli-coil glowing.
     
    #38
  19. craig moss

    craig moss Member

    Joined:
    Sep 29, 2006
    Messages:
    572
    Likes Received:
    5
    How much boost? The springs are on the weak side for a bunch of boost for that combo.
     
    #39
  20. sune

    sune Member

    Joined:
    Jun 20, 2009
    Messages:
    141
    Likes Received:
    0
    There are no heli coils in the spark plug threads

    Boost is about 30 psi
     
    #40

Share This Page