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  1. #1
    Member
    Join Date
    Jan 2009
    Location
    Western Australia
    Posts
    33
    Corvette(s)
    1984 bright red

    Help Back fire thru t/bodies

    Hi Guys, I have a problem that is bugging me to no end.
    I have just o/hauled my engine,fitted flat top pistons,Crane 2040 cam,Patriot 190 alloy heads,Headman long tube headers, and a Renegade inlet manifold.
    I have fitted a 85 fuel pump. My t/bodies have been bushed and bored to 2".
    I have started engine,set timing to12 degs BTDC, fuel pressure set at about 18lb on guage. Engine idles OK, but it bangs out tail pipes.
    To car for run up the street,under throttle engine backfires out t/bodies,as if timing is wrong,returned to shed rechecked timing OK.
    Stripped front of engine to recheck cam timing ,all OK.Reassembled front and tried again,same problem.Have changed the Distributor twice,new Accell unit and the original.
    I know that the comp ratio is abit high 10.2-1,I run premium fuel 96 octane,no detonation as yet.
    Can any body tell me where else to look,not sure what could be the problem
    Have removed and replaced inlet manifold gaskets to make sure no leaks etc
    Thanks

  2. #2
    New Member
    Join Date
    Dec 2008
    Location
    Maryland
    Posts
    13
    Corvette(s)
    1984 Dark Bronze,58 White

    Default

    When setting the timing are the marks ok mybe the balancer turn and marks are off,happen to me before.take this the right way but sounds like plug wires are mixed up the dumb things have got me in trouble before.Are the valves adjusted right?Can't think of anything else.Let me know what you find.

  3. #3
    BigJimZ16's Avatar
    Join Date
    Oct 2008
    Location
    Portage, Indiana
    Posts
    849
    Corvette(s)
    2004 Z06 CE & 2010 Grand Sport Vert JS Blue

    Default

    Quote Originally Posted by DPC Racing View Post
    When setting the timing are the marks ok mybe the balancer turn and marks are off,happen to me before.take this the right way but sounds like plug wires are mixed up the dumb things have got me in trouble before.Are the valves adjusted right?Can't think of anything else.Let me know what you find.
    It wouldn't be the first time 5 and 7 got crossed...
    The only thing that you accomplish when you make something idiotproof, is breed a better grade of idiot,
    Z06/Z16 #1689

  4. #4
    Member
    Join Date
    Jan 2009
    Location
    Western Australia
    Posts
    33
    Corvette(s)
    1984 bright red

    Default Back fire thru T/bodies

    Guys, I think I may have found the problem.
    After doing so study regarding my problem,I stumbled upon the subject of Dist rotor phasing.I checked the position of the rotor on #1 cylinder at 12deg and found it to b e between 1 & 2,but slightly clopser to No 1.I removed thye Dist to try and get the rotor more in line with the cap post,but ende up in between 1 & 8 by the same amount.Reghardless of where I fitted the Dist same problem.
    Drilled 2 large holes in cap either side of No1 post and started engine with tim ing light connected,with brown wire disconnected for the timing,rotor appeared Ok but not right,connected the brown wire and restarted engine,took engine up to about 1500-1800 revs and it appears rotor is too close to No 2 and it starts to back fire if anymore revs are used,the advance is causing the problem.
    This problem has happened since I cahanged cam & dist. The gear on dist is slightly in a different postion where it has been drilled for the locating pin.
    I have ordered a adjustable rotor fromthe USA,hopefully this will fix the problem
    Cheers

  5. #5
    New Member
    Join Date
    Dec 2008
    Location
    Maryland
    Posts
    13
    Corvette(s)
    1984 Dark Bronze,58 White

    Default

    I don't think that's your problem,if the timing with the light is right on 12 and the marks are right that is what you got.The phasing is nice to have right on but never is.I think you should be looking some were else.Coil,module,injectors etc.Broken valve spring,wiped cam I wish I could help you more

  6. #6
    Member
    Join Date
    Jan 2009
    Location
    Western Australia
    Posts
    33
    Corvette(s)
    1984 bright red

    Default Back fire thru T/bodies

    Thanks Guys,I found the problem,The new dist module must be faulty. I changed the module out of my old dist retimed engine,no back fire.
    I checked the advance on dist with light,it dosent appear to advance up as much,not sure why.
    To prove the point I changed back the modules and back fire was back.
    I am going to order a new module for my dist,anybody know the best one to get to fit my dist
    Thanks again for the replies
    Cheers

  7. #7
    New Member
    Join Date
    Dec 2008
    Location
    Maryland
    Posts
    13
    Corvette(s)
    1984 Dark Bronze,58 White

    Default

    Glad you found it ,new parts that are bad really drives me crazy at times.I have had luck with stock ones [Delco].Let me know how all the new mods work when you get it running right. Take care Dan

  8. #8
    Member
    Join Date
    Jan 2011
    Location
    columbia city in
    Posts
    113
    Corvette(s)
    1982 red corvette

    Default

    thats a good find .i would have looked at a lot of other things before i came back to that.

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