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Thread: kick back while starting

  1. #1

    kick back while starting

    new engine bbc 15.1 comp kicks back when starting and sneze's thru the carb when starting. have 36 total locked timing and the msd programable 7 has 20 degrees retard while cranking. i always crank the engine to spin before ignition is turned on. any help or ideas. i know the flex plate and started wil be trash soon. i have on order a 16 volt battery but still waiting for it. i curently have two yellow top batterys tied together

  2. #2
    Senior Member MASTER BUILDER
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    Take out the start retard. I've busted every flexplate and/or starter I've used with retarded starting.

    George
    http://www.gdmii.com/pics/81launchvidcapsig.jpg
    1981 Camaro @ 2594 lbs.
    496 cu. in. on 1150 Rupert alky
    Brodix BB2X heads touched by the magic hands of Curtis Boggs
    5.470@125.56 Best 60' 1.18
    www.motorsportsvillage.com

  3. #3
    Administrator RACING JUNKIE
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    Quote Originally Posted by gdmii
    Take out the start retard. I've busted every flexplate and/or starter I've used with retarded starting.

    George

    X2
    There Is 1 Thing Better Than Cubic Inches,,,More Of Them

  4. #4
    Senior Member DYNO OPERATOR
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    Tell me how the start retard is causing an engine to kick back IF the rotor is correctly in phase?

    You have the rotor at let us say in his example of locked distributor at 36 degrees. If your rotor is correct in phase at that 36 deg timing, when you retard the ignition for starting, electrically it will also retard the rotor position by 20 degrees with a 20 degree retard. That puts the rotor at now 16 degrees BTDC. How in the crap is 16 degrees BTDC going to cause a kick back? I settled on that for my car a 25 degree retard worked best. The 30 degree moved the rotor position too far toward the next coil tower post and did cause a kick back. REtail versions came out with 20 degree retards.

    I designed and develpoed the original start/run retard and I tried every amout of ignition advance from 10 deg up to 30 degrees to find what would be better. My test car had 16.85 -1 compression too. Both Warren Johnson and myself did the testing on the first two protype units. I feel that I am very qualified to talk about this eventhough the original one has long since been replaced with newer digital versions.

    By You spinning the engine over and then turning on the ignition switch, you have already defeated any concept of how start retard works.

    KIck back is caused by several possible reasons, none of which is the MSED Start Retard when correctly used.

    1
    Excess fuel in the chamber/cylinder prior to 1st plug firing.
    2
    Engine electrically swapping cylinders becuase of rotor out of phase. The path for electrical energy to the next nearest coil terminal is easier than to the one supposed to be firing. It is easier to fire a cylinder with little to no cylinder pressure than it is the one under pressure with the closed valves.
    3
    Crank Trigger gap is too wide, causing a conflicting initial trigger signal from between the distributor and the crank trigger. Check the MSD WEbpage about Crank Trigger gap adjusting. I usually set that gap at .055 to .060

    If you are kicking back and breaking teeth on flywheels it is also hard on rod bearings.

    Ed
    " Let all things that hath breath, praise the Lord. Praise Ye the Lord" Psalms 150 vs 6.

  5. #5
    Senior Member MASTER BUILDER
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    Ed,

    In theory, everything you said above is true to my knowledge. I think, however, the problem with start retards lies in the way it does the retard, which is electronically. I don't know how much voltage is required of the system for the retard to work flawlessly everytime but I have a hunch that at some point in the crancking process there is a draw down in the voltage that causes the retard to drop out and back in. That's just my own theory. I've never put a meter on it to try to find the problem. In my own experience, I have tried two different model MSD retards and either broke a flexplate or starter with both of them on more than one occasion. I took the retard out and haven't broken anything in over 2 years.

    You are much more qualified to speak of the hows and whys than I am but I have never had good luck with them. It's kinda like I can't tell you how to do an appendectomy but I know that when the appendix comes out there is no more pain. I took the start retard out and now I have no more pain of broken parts. I don't run a crank trigger although I am putting one in before next season.

    One other thing...if spinning the motor over before turning on the ignition totally negates the start retard function, why isn't there a caution in the instruction to this effect? I've never seen any mention of this.

    George
    http://www.gdmii.com/pics/81launchvidcapsig.jpg
    1981 Camaro @ 2594 lbs.
    496 cu. in. on 1150 Rupert alky
    Brodix BB2X heads touched by the magic hands of Curtis Boggs
    5.470@125.56 Best 60' 1.18
    www.motorsportsvillage.com

  6. #6
    Senior Member DYNO OPERATOR
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    George,
    It does not electricically negate it at all. It is very much in force if it is activated. What I mean is if you spin the motor over and flip the switch it negates any possible benefit of using it and can be more destructive than good, becuase the thing is still with a retarded spark no matter when you flip the switch. If you are going to spin and flip the switch completely disable the start retard and do not allow it to do any retarding. It is designed and works very well at retarding the ignition a set number of degrees the same as if you were manually twisting the distributer to retard one to get it to start.

    The spark is not delayed. It is the time it takes the trigger signal to get to the power supply that gets delayed. In the original versions we were using resistors of different values shunted to ground to delay the trigger for either starting or for the extra high gear retard. These resistors of different values were labled simply as degrees. Different values were different resistances. It was the same way in essence the rpm rev-limiter worked, each different chip was a resister of a different value.

    I have a customer with a hard head that refuses to use the retard and he also spins and flips and he keeps knocking teeth. I have told him the same I am telling all of you. Before we had a start retard we then did spin and flip and we ocassionally lost teeth and at times bent rods. We means all the racers of those edays before MSD.

    Just think if you will. How can an engine possibly kick back. What can cause it. With a regular car timing too far advanced will do it. Why? When you change the timing either by manual, mechanical, or electronic means, the rotor position when fire hits it is also changed. IF it is easier for fire to jump to # 8 or # 2 it will before it will jump to #1 which is under pressure. So the rotor does not have to be far away from center #1 position to jump the fire to either #8 or #2.

    If you have your rotor lined correctly in the right spot and a locked distributor it will be centered at #1 coil terminal at your maximum timing. Retarding it will move it away from ideal center but not so far that # 1 is still not the preferreed cylinder to fire. IF you have for example a 30 deg locked distributor and it is locked at 30 degress advance but it is a N2o motor, so you are mostly at maybe 15 degrees advance all the time. or maybe even at 20 degrees.. So even with rotor phased correct for nitrous use it would still be very close when retarding from total timing with no N2o. Actually it would be almost dead center or close to it with the start retard but not the nitrous retard. So ignition wise there is no way it could kick back.

    Now if you were to take the secereo I just outlined in the above paragraph and were to still have the ignition retarded for starting only and were to spin it and flip the switch, the first or next cylinder to come up should be the one to start the starting process with or withour retard, but not so. Becuase then that cylinder has already hit and gone past TDC becuase of the retard and the next cylinder to fire is likely a piston on the way up and not ready to fire or worse yet a cylinder with an open valve. Remember the engine only fires every 90 degrees of rotation. So depending on where in rotation it is when you spin and flip will depend on what happens afterwards. Excess fuel in the cylinder is a sure way for a kick back. That happens far more frequently than you can imagine it does.

    IT was becuase of parts breaking that we came up with the retarded start in the first place. Usually it was a starter or flywheel tooth. At timmes guys had rods bend. Most of the time they all got away with it no problems.

    I know that the newer Digital Boxes are not working exactly the same but I think the concept of it is. I know the guy who created all the Digital Boxes, I am thinking about talking with him about what you all are saying and maybe someway it can be switched of and on like in the old days instead of being rpm sensitive. Maybe that can be an issue, come to think of it.

    Ed
    " Let all things that hath breath, praise the Lord. Praise Ye the Lord" Psalms 150 vs 6.

  7. #7
    i checked the distantance of the pick up and it was .075 i did reduce it to .057. as far as the rotor phaseing it put #1 at 38 degrees on the pointer and the rotor was inline with the terminal on the cap. just to talk about the fuel issue what i sat may have no bearing, but let me tell you what changed. i used to have a black holley with the old engine and would always turn the pump off about 5 to 10 seconds before the engine after each round. i now have a aero motive 2000 and when i doo the same the fuel pressure guage stays a 7 lbs for that same 5-10 seconds. it would eventualy bleed down but when i dont know. with the black pump it did'nt have a regulated bypass to the tank and the fuel pressure would drop as the motor ran with the pump off. i'm just wondering with the new set up when the pressure finaly bleeds down, where is the bleeding going?" to the motor or the gas tank.

  8. #8
    Senior Member MASTER BUILDER
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    Check your mag pickup polarity,it causes all sorts of problems if its reversed.we have found many MSD distributors with the magnet upside down reversing the polarity of the pickup.even if you plug the dist in with a msd plug it can be wrong. to check this unplug your dist and make up a pair of short wires.plug one end into the dist and cross the wires and plug them back into the loom. start your engine and see if the timing advanced or retarded. the correct polarity with an analog box is the most retarded position. with a digital box its the most advanced position.
    also make sure the orange and black coil wires are not in the same loom or running parallel to the mag pickup wires. the 600 volts or in those leads will induction fire the box and cause all sorts of engine damage like piston or bearing failure on a engine with correct clearances and tune up.Bill
    Hendrens Racing Engines
    1310 U.S. Hwy 221 North
    Rutherfordton N.C. 28139
    828-286-0780 Bill, Steve, Mike
    www.hendrensracingengines.com


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