Blown head gasket

Discussion in 'Manton Push Rods Top Alcohol Tech Questions' started by Neil Morley, Mar 27, 2018.

  1. Neil Morley

    Neil Morley Member

    Joined:
    Dec 28, 2015
    Messages:
    93
    Likes Received:
    3
    I've got a question on my blown BBC , I banged the blower on my last outing and popped the burst panel, after tear down and inspection the only damage I can find is it blew the head gasket on number 7 cylinder and bent the wrist pin (.250" wall) , the rod and all the bearings are fine and look like new the piston and are fine and no Fire slotting to the block or heads but it happened right after the 1/8 mile and it was on the rev limiter for probably 1/2 second which is set at 8,100 rpm, the only thing I can think is did it possibly over fuel that cylinder while on the rev limiter and hydraulic that cylinder?? Or what? And why did it pop the burst panel and bang the blower with no damage to anything else???
     
    #1
  2. Mike Canter

    Mike Canter Top Dragster

    Joined:
    Mar 10, 2004
    Messages:
    4,060
    Likes Received:
    60
    No way it would be too much fuel. All your symptoms indicate detonation from too little fuel or too much ignition advance.
     
    #2
  3. Unlimitedaero

    Unlimitedaero New Member

    Joined:
    Oct 26, 2014
    Messages:
    29
    Likes Received:
    1
    Bending a .250 wall pin? Gotta be detonation. Check the pin bosses for cracks carefully and bore dimensions.
     
    #3
  4. kosky racing

    kosky racing Comp Eliminator

    Joined:
    May 11, 2003
    Messages:
    575
    Likes Received:
    19
    Positively the rod is wobbled and the piston is junk- put a pin thru piston and it will go clunk-bent bosses
     
    #4
  5. Neil Morley

    Neil Morley Member

    Joined:
    Dec 28, 2015
    Messages:
    93
    Likes Received:
    3
    I'm not doubting you guys in any way but if it were lean or detonating wouldn't it show in the rings or ring lands or bearings??? Especially since it bent the wrist pin and pushed out the head gasket with no fire slotting? Again I'm not doubting just want to make sure you have all the facts to base your opinion but it did pop the burst panel like a lean pop ? Looking at the data of the previous 2 runs the EGTs were a little warm but I was trying to pay more attention to my plug readings as it was burning only half the cadmium around the base of the plugs , it's a 990 pump and my fuel pressure on the prior runs was 165 psi with a .095 main and a .065 high speed, it's a conventional headed 555 CI BBC and I'm running 34 degrees total and pulling it back to 28 above 5000 rpm I was wondering if I could cut that back to 26 degrees above 5000 rpm without sacrificing mph?its a 14/71 high helix 38% OD and makes 40 psi at 8100 RPM and that's where my rev limiter is set. But you don't think being on the rev limiter too long had anything to do with my dilemma? Sorry for the long post but just want to learn and prevent this from happening again, thanks!
     
    #5
  6. Unlimitedaero

    Unlimitedaero New Member

    Joined:
    Oct 26, 2014
    Messages:
    29
    Likes Received:
    1
    I run a similar combination but 14 degree Big Chief heads. 40 Lbs of boost and no more than 30 degrees of timing. Around 13.5 GPM at 8000. My plugs tell me I'm safe at that. Might comparing apples and oranges tho.
     
    #6
  7. Will Hanna

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

    Joined:
    May 6, 2003
    Messages:
    6,333
    Likes Received:
    50
    detonation is hard to see on plugs. about the best indicator is a dark colored plug. also the reason why it didn't tear anything else up may be due to the fact when the head gasket let go, it relieved the cylinder of pressure. typically you can run more timing with rpm than you can at lower rpm. at lower rpm the engine is loaded harder and has less fuel due to lower pump speed.

    there could be a number of causes, but the first thing i would do is drop the timing and put some fuel in that cylinder. way easier to work from rich to lean than lean to rich...
     
    #7
  8. rb0804

    rb0804 Member

    Joined:
    Aug 7, 2010
    Messages:
    440
    Likes Received:
    7
    It’s tough to say without having all the parts to review in person. Did the piston touch the head? Any witness marks on the head or the piston? I would pull the head apart and check the intake valve for straight and to see if it’s sealing. The panels only come out if you the intake valve doesn’t seal or if the cylinder is so lean that it glow plugs and when the intake valve opens it ignites the incoming charge. What bearings are you running? What did the EGT do for that cylinder? In addition I personally feel that it’s near impossible to hydraulic an Alcohol engine. Nitro, that’s a different story.
     
    #8
  9. Neil Morley

    Neil Morley Member

    Joined:
    Dec 28, 2015
    Messages:
    93
    Likes Received:
    3
    I've been running a clevite coated H bearings with no issues so far and no there is no sign of the piston making contact with anything, I hate to slow the car down since it's been running good and really coming around but better than tearing up parts and it seems the consensus is that the rev limiter had nothing to do with it, my EGTs were the hottest on cylinders 1 and 6 but since the plugs were burning less than 1/2 the way around I wasn't too concerned but cylinder 7 is the one that pushed out the gasket??? thanks again I value and appreciate all your opinions and hopefully I will
     
    #9
  10. Dave Koehler

    Dave Koehler Member

    Joined:
    Sep 10, 2004
    Messages:
    384
    Likes Received:
    5
    Neil,
    If you think going richer will slow it down while you investigate this, don't bet your cookie stash on it. Your plugs might be indicating that you are not burning enough fuel to make the heat. That may sound a bit left field but it can happen. Only one way to find out.0.

    Something else to throw out there. I don't know where you are but you didn't get caught with a hot weather tune on a crisp day?
     
    #10
  11. GTPerf

    GTPerf Member

    Joined:
    Oct 22, 2006
    Messages:
    193
    Likes Received:
    4
    did you say what Ign you are running and are you using a crank trigger ? What Spring pressure ?
     
    #11
    Last edited: Mar 28, 2018
  12. rb0804

    rb0804 Member

    Joined:
    Aug 7, 2010
    Messages:
    440
    Likes Received:
    7
    Clutch or converter? Something to think about, adding fuel may make your problem worse...depends on what is going on. That’s why Mr. Canter said add fuel and take out timing.
     
    #12
  13. Neil Morley

    Neil Morley Member

    Joined:
    Dec 28, 2015
    Messages:
    93
    Likes Received:
    3
    I'm running a power grid ignition and yes with a crank trigger and the air was actually better the day before with the same tuneup and I'm running a power glide with a convertor , is it possible the reason I'm seeing 1300 degrees on the EGTs and very little heat on the plugs that maybe I'm building a header fire or only 28 degrees of timing for a conventional headed BBC with only 10.7 compression that it's burning late into the pipes??? I've never had an issue before until I was on the rev limiter that long at the end of the run???
     
    #13
  14. BEDNAR1320

    BEDNAR1320 Member

    Joined:
    Oct 8, 2008
    Messages:
    215
    Likes Received:
    10
    When you say blew the head gasket on #7, did it blow between cylinders into #5, or come out somewhere else?
     
    #14
  15. Neil Morley

    Neil Morley Member

    Joined:
    Dec 28, 2015
    Messages:
    93
    Likes Received:
    3
    It pushed it to the rear towards the water jacket and didn't even pressurize the cooling system and didn't even leave a carbon trail on the block or head so that's why I think it hydrauliced because if it was cylinder pressure I would think it would have blown out water and fire slotted something wouldn't it???
     
    #15
  16. BEDNAR1320

    BEDNAR1320 Member

    Joined:
    Oct 8, 2008
    Messages:
    215
    Likes Received:
    10
    What head gaskets are you using?
     
    #16
  17. turbo69camaro

    turbo69camaro Member

    Joined:
    Nov 26, 2007
    Messages:
    226
    Likes Received:
    6
    lol love playing detective....Are you running a mag ? What kind big or small cap? It could be banging on the limiter that long you had a miss fire.The piston was out of place when it fired big pressure spike bend the pin pushed out gasket.If gasket pushed out into cly 5# bang goes the blower.The piston on that cylinder will be junk for sure even if the pin bore of the rod is ok the rod got over stressed and should be cycled out also 1300 on egt's thats burning fuel in the pipe a chevy motor should be happy at 32-34
     
    #17
  18. Neil Morley

    Neil Morley Member

    Joined:
    Dec 28, 2015
    Messages:
    93
    Likes Received:
    3
    SCE Titan .060" copper head gasket with new century aluminum block with O-ring and receiver grooves in the head and no it didn't push out to cylinder number 5 but rather to the back towards the firewall into the water jacket and didn't even leave a carbon trail and didn't pressurize the cooling system???
     
    #18
  19. BEDNAR1320

    BEDNAR1320 Member

    Joined:
    Oct 8, 2008
    Messages:
    215
    Likes Received:
    10
    My New Century block has O-rings in the head and grooves in the sleeves. .070 Flatout gaskets, usually around 28-30# boost with no problems. I run 24° timing with my 12° heads. Do you torque your heads from the center out or from the ends in? 1/2" or 7/16" studs?
     
    #19
  20. Neil Morley

    Neil Morley Member

    Joined:
    Dec 28, 2015
    Messages:
    93
    Likes Received:
    3
    7/16" studs and have always torqued inside out and 24 degree head with 28 degrees timing and 40 lbs boost with a very heavy door car 3850lbs (grudge car) and I actually pull timing with the grid on the hit but when this occurred at the end of the run all the timing should have been back in!
     
    #20

Share This Page