Problems again...

Discussion in 'PSI Superchargers Tech Questions' started by Adamfl, Aug 3, 2009.

  1. Adamfl

    Adamfl Member

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    As i wrote in a previous thread, I had/have problems with my BAE stage 6 (Pro Mod)motor. The problems I had before were "missfiring" at high rpm.
    Before this weekend we changed the: Mag, points box, two step, plugs, vires, coil etc.
    The first run out this weekend was a clean 6.18s run. It felt good, so I thought the problem were fixed, but when I got back in the pit and watched the computer I saw that the EGT on nmbr 4 cyl raised after 5.9s. When I checked the spark plugg it was burned off...
    The temperature on nmbr 4 were only 980dgr. We changed the piston and rings and made another run, then it missfired after appr. 4 sec and blew the burst panel and belt. When i checked the motor in the pit nmbr 4 piston and plug were bad again.....:(
    Any ideas???
     
    #1
    Adamfl, Aug 3, 2009
  2. Rodney O. Trower

    Rodney O. Trower New Member

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    Lean, its just lean fatten er up and put a 120 down piston in that hole.
     
    #2
    Rodney O. Trower, Aug 3, 2009
  3. Adamfl

    Adamfl Member

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    Im running it much fatter now, than before this problems started..
    I can see that both on the EGT:s and on the fuel flow log.
     
    #3
    Adamfl, Aug 3, 2009
  4. Bob Kraemer

    Bob Kraemer New Member

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    Sometimes you can be to lean to hurt anything, then when you richen it up you are still to lean but now have enough fuel in it to hurt stuff.
     
    #4
    Bob Kraemer, Aug 3, 2009
  5. Will Hanna

    Will Hanna We put the 'inside' in Top Alcohol
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    overall lean

    you might just have a lean hole or the over all system is too lean and it's going to pick on whatever cylinder is doing the most work. as mentioned above you can deck the piston or put a short rod in that hole without having to put a big nozzle in it and mess up your nozzle area.

    If you have a racepak, check your cc's per turn to make sure it's a flat line. regardless of what the number is, it should be flat. if it's not flat, you have a problem somewhere.

    Do you run a crank trigger? I've seen a magnet go bad on the degree wheel and it will drive you nuts because you change everything else. If so, just make a run off the mag and see if it misses.

    Are the heads grounded to each other, all of that good stuff?

    Start looking at the lowest common denominators...what is still on the car in the ignition process from the battery to the spark plug that you haven't changed.

    Do you have a tach converter on the car? I've heard of those going bad.

    Another thing on new points boxes, MSD doesn't really crimp the boxes as good as they used to. You'll notice the inserts where the mounting bolts go through are probably loose. You need to peen those with a punch or something to fix that. It's also a good idea to run a nut between the bolt and the mount with another ground to it to ground the box itself.

    On Rick Jackson's car, they went round and round chasing a problem like you mention, ends up the hot side of the coil was close enough to the points box it was arcing over during the run and frying the points box. They would do the same thing, make one good run or half a good run, then a dead box, missing, etc. It finally left a carbon trace and they rotated the coil to get it away from the box.

    What kind of kill switch? If it's a Johnny West, it has to be cleaned with a small wire every time it's used. Either change the switch or make a run without it connected to see if that eliminates the problem. More times than once I've seen the kill switch wire or another wire have a small cut in the insulation going between the mounting plate and frame, causing a short.
     
    #5
    Will Hanna, Aug 3, 2009
  6. Adamfl

    Adamfl Member

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    Thanks for the replies!

    I have tried all the things that Will suggests...
    The thing is that before this problem started Ive made appr. 30 runs with it much leaner than now, so I dont think its a fuel problem. When the problems started two weeks ago I made 5 runs and it only missfired, now its burning nmbr 4 piston every run. Before this weekend I changed the mag, can it be the mag?
    The last run it allso blew the burst panel and belt, doesnt that mean that its firing when the intake valve is open?
    As i said before, the EGT:s is normally around 1070 dgr, and now they are only 930-980dgr. The fuel flow allso shows that its much richer now.
     
    #6
    Adamfl, Aug 3, 2009
  7. Rodney O. Trower

    Rodney O. Trower New Member

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    Burst panel leaving, and piston melting its screaming LEAN its a fuel problem colapsed or partially plugged line or injecter. Perhaps one of your crew recently pinched the fuel line to that injector in the valve cover Its also the easy fix, if you have done what Will suggested then its LEAN....
     
    #7
    Rodney O. Trower, Aug 3, 2009
  8. Dale Finch

    Dale Finch Member

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    Hi Adamfl, I agree it is screaming too lean. You can be so lean it won't hurt itself. A small step richer and the rods will come out. I would start back rich unless you like building and paying for engines. I can't remember if you said you had a computer. How many gpm at 8500 and 9500 if it has gotten there. Think the next move carefully.
     
    #8
    Dale Finch, Aug 3, 2009
  9. jim phillips

    jim phillips ta/fc

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    im sure i dont know as much as some of the guys on here if it was mine i would be looking to raise the port nozzle are check the line to the nozzle as stated above are the nozzle its self it sounds like it could get expenseive real quick good luck
     
    #9
    jim phillips, Aug 3, 2009
  10. Adamfl

    Adamfl Member

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    OK, I understand that it sounds like its to lean I just cant understand why it all of a sudden can get that lean... Ive made 30 runs with the motor, and tuned it much harder?
    Fuel flow at 9500rpm is 13.3gpm and at 8500rpm 12.45gpm.
    The warmest EGT is 986dgr and is the cylinder with the bad piston...

    Thank again everybody...
     
    #10
    Adamfl, Aug 3, 2009
  11. Worms

    Worms Member

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    This is so true, it's a pity that some people just don't see that.
     
    #11
    Worms, Aug 3, 2009
  12. Will Hanna

    Will Hanna We put the 'inside' in Top Alcohol
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    head temp

    do you monitor head temp? the bv didn't get changed and jack the head temp way up did it?

    egt's at stage does not always equal a certain head temp. one of the biggest misconceptions out there...
     
    #12
    Will Hanna, Aug 3, 2009
  13. wildride boy

    wildride boy Top Sportsman Racer

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    Did the rods brgs hurt ? How they look
     
    #13
    wildride boy, Aug 3, 2009
  14. JP

    JP Member

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    Sometimes when we change stuff around in the tune up some cylinders will change the way they run so we change the port nozzle to get it safe but we have never changed them more that .004 and we keep always the same area by moving fuel around rich-to -lean nozzle changes.


    Will you made me think on the fuel cc graph, what kind of trouble can it show?

    Mine is definitely not an straight line


    thanks!
     
    #14
    JP, Aug 3, 2009
  15. Mike Canter

    Mike Canter Top Dragster
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    The mag, coil, rotor, and points box are stupid. They don't know one cylinder from the other so they can't just pick on number four. The cap, wire and plug are unique to one cylinder. I would also guess the fuel system. I would swap that port fuel hose with another cylinder or just replace it. Could be coming apart inside. Compare the heat on the threads of plug four with all the other plugs. Are they the same or does plug four have more heat in the threads. Is the piston melting in the middle or on the edge?
     
    #15
    Mike Canter, Aug 4, 2009
  16. Dale Finch

    Dale Finch Member

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    Sometimes all is not as it appears. Maybe there is a flapper in the main fuel line or some such problem. It may be a micro second or two that starts to snowball rolling. I had this very situation on a dragboat years ago. When the fuel system went on the flow bench the problem was found. Never burned a piston again or broke the belt due to a lean condition again.
     
    #16
    Dale Finch, Aug 4, 2009
  17. Adamfl

    Adamfl Member

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    Well, the thread on the plug does not show more heat than the other ones(actally it doesnt show any heat at all...), but its melting in the center.
    The piston is collapsed in the midle.
    Yesterday I checked the fuel system and found blower lube in two jets in the hat nozles... I guess we used to much lube in the blower, because the hat, intake and blower were full of it.
    Shouldnt the fuel just wash it away??? Can this be the problem?
    There were no problem with the port nozle or the fuel line.
    The head temp were the same as all the other runs I made.

    Thanks guys...
     
    #17
    Adamfl, Aug 4, 2009
  18. Mike Canter

    Mike Canter Top Dragster
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    I have always bee taught that when a piston goes on the edge it is detonation but when it goes in the middle it is more than likely pre-ignition. Maybe someone out there can comfirm this. If it is pre-ignition then that explains why you can't find the problem. I would either check the inside of the mag cap with a bright light and magnifying glass for carbon tracks around number four or just replace it. Also cross fire from bad ignition wires can cause that. Also if you have a crank trigger you need to check your rotor phasing. This pre-ignition would confirm your confusion on why did something change in your fuel system that you cannot find. It is worth looking into.
     
    #18
    Mike Canter, Aug 5, 2009
  19. B.DOUCET

    B.DOUCET New Member

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    Another thing to look for is a out of round cylinder are a intake leak that can suck oil at idle are after the burnout. Oil in the cylinder will cause it to burn the piston.
     
    #19
    B.DOUCET, Aug 5, 2009

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