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Checking deck height

Discussion in 'T-Bucket Engine and Driveline Articles' started by volksnut, Jul 6, 2017.

  1. volksnut

    volksnut
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    I discovered on disassembly of my T's 350, it was actually a .030 over 355. That's the good but the bad is has low compression dished pistons. I did a quick deck check and the outer portion of the piston is .050 in the hole and the center is .140 That seems like a lot doesn't it? I'll need to cc the center of the piston to determine dish. I wanted to install some 64cc heads to bring the compression up, but doesn't look like it will achieve much.
     

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  2. fletcherson

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    It depends on what you want it to be. If you just want a smooth cruiser to run on pump gas or a blower motor, lower compression is your friend. Pistons aren't cheap like they used to be...
     
  3. Spanky

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  4. Indycars

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    Yes, 0.050" deck height is on the upper limit for providing good turbulence at TDC. Also
    the piston you have has very little quench area, also not as good as it could be. See pics
    below for an example. Now maybe at the compression ratio you have, there is no detonation.
    But if you raise it up, in the neighborhood of 8.0 to 8.25 dynamic compression ratio, then
    the quench area will become important to stopping detonation.

    Yes you really need to run the numbers and know exactly what you are dealing with ...... don't guess.

    Not good:
    DishedPistonNoQuench.jpg

    Much better:
    DishedPistonGoodQuench.jpg
     
  5. 2old2fast

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    With all the good/inexpensive parts available you can easily put together a solid reliable 400-450 HP/450 #ft torque sbc for $2500-$3500 , there's really no point in messing w/those pistons/bottom end..
     
  6. roadmonster

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    I can tell you from experience that 64cc heads are likely to knock on pump gas. I run camel hump heads on a .040 over (357) 310-320 hp motor with thick Felpro gaskets to get the compression down to the low 9s. I had small-valve Power Pack heads at one time with even smaller chambers, but could never quite tune the knock out. Going from about 11.4 to about 9.2 CR really mellowed things out and produced a wide powerband with great sound. If there is any power loss, it's not noticeable. You will lose a little wheelspin and a little 2nd-gear chirp, but that's it.
     
  7. roadmonster

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    Sorry, just remembered my pistons are flat tops! Looked at some old build photos. If you have about 10ccs or so, small chambers should work fine.
     
  8. fletcherson

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    I too battled the ping monster on my stroker. It had flat top Pistons cast iron 882's, 600 lift, 290 duration cam, dual plane intake with a 750 eddlebrock. I finally resolved it with a timing computer from msd, but the poor fuel quality makes it very challenging to tune a stout street engine. The reduced timing required to try to reduce preignition really defeats the power and kills performance. I spent many hours and dollars tuning that engine. Aluminum heads and reduced deck height helps because it reduces the heat, but high compression engines don't fare well on pump gas.
     
  9. RPM

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    Yep the days are long gone of 12.5 compression on the street and buying Sunoco 260.
     
  10. fletcherson

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    Oh, the good days!
     
  11. Spanky

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    Yeah . . . Sunoco 260 was blue colored, and Gulf Crest was tinted kinda purple!:confused::rolleyes::eek:
     
  12. volksnut

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    Flat tops on the way...makin my T great again :)
     
    Spanky likes this.






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