Ignition Timing Changes with a Shorter Stroke Crank

Discussion in 'PSI Superchargers Tech Questions' started by Blown5402, Nov 11, 2013.

  1. Blown5402

    Blown5402 Member

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    How much can the total ignition timing be changed when going to a 1/2" shorter stroke crank on a BAE Fathead 5 safely with 50#s of boost on alcohol? THANKS for any information!
     
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  2. Blown5402

    Blown5402 Member

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    24 degrees now

    We are running 24 degrees now and need a few more hundreds now. Thanks!
     
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  3. Mike Canter

    Mike Canter Top Dragster
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    The amount of ignition timing is dependent of flame front travel which consists of sparkplug location and design of combustion chamber which includes compression ratio and type of fuel. Do you know how much you changed your compression ratio with the stroke change? What was it before the change and what is it after the change?
     
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  4. Blown5402

    Blown5402 Member

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    10.25 comp ratio-438ci BAE 5 Fathead

    Mike, we are keeping the 10.25 comp ratio (438ci motor) and the heads are BAE 5 Fatheads. I need a little more timing and have not run more than 24.5 and have made the goals for this year, but now going into the 3.90s and need just a little more to go with a 100# diet this Winter on the chassis. I need to pick up .02 to .03 more with the 100# diet and should be OK for next season locally. THANK YOU for any help and many have said 25 degrees total timing on the Fathead 5 is plenty. I just wanted to know if in someone's experience; will the shorter stroke take anymore timing safely? THANKS, Jim
     
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  5. Mike Canter

    Mike Canter Top Dragster
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    I would stick with no more than 26*
     
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  6. Blown5402

    Blown5402 Member

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    Thank you and may stop at 25, if we can run low 3.90s stating fat!

    Mike, Thank you and may try 25 degrees and stay very fat and adjust the timing coming in earlier and shoot for low 3.90s with the little motor! Thanks, Jim
     
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  7. iron468

    iron468 Member

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    i have 3.900 stroke 4.310 bore (456ci)14-71hh bae5 head msd 44 big dome 35lbs boost i'm run at 27 rod bering always good
     
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  8. Nitro Diver

    Nitro Diver Member

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    What about rod/stroke ratio, if you use a shorter stroke with a longer rod to keep the same compression the piston will dwell longer at the top and build more cylinder pressure, would this mean that less timing would be needed??
     
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