Piston to head clearance too tight?

Discussion in 'Engine Topic' started by Mwilson, Dec 6, 2017.

  1. Mwilson

    Mwilson Veteran Member

    looks like he went down to .024!
     
  2. tom3

    tom3 Veteran Member

    10,669
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    Aug 1, 1999
    ohio
    Interesting to see pistons above the deck. I wonder if there are any negatives with that besides the quench deal?
     
  3. 70lt1z28

    70lt1z28 Veteran Member Gold Member

    1,275
    138
    Oct 3, 1999
    Beavercreek, Ohio, USA
    Typically that means a deck that has been cut a bit much. This can cause issues with the intake manifold not sealing or needing cut to match the deck height reduction. Also can lead to valve train geometry issues so that shorter pushrods are required.
     
  4. SRGN

    SRGN Veteran Member

    260
    67
    Feb 20, 2009
    Central NJ
    .040 is a decent number to shoot for. .035 will be good if your tune is dead on and bearing clearances stay tight. I've gone lower on some max effort N/A combos, made great power. When the ones that ran the best numbers were torn down for freshening, you would see a "shadow" of the piston on the aluminum head surface. Not an imprint, just enough to let you see the piston was right there. This was LS stuff shifting at 7k. Look up squish and quench on Google when you have multiple hours to kill. Lots of good info out there.
     
  5. G72Zed

    G72Zed Veteran Member

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    Sep 8, 2015
    Canada
    Agree, but a "short" deck also allows you to shave the piston tops down to get the P to H clearance right on the money, reduce valve reliefs & crevice volume, not to mention higher top ring placement, and the shorter pushrods are a positive. More work, but not all negative.
     
  6. Rdobbs1977

    Rdobbs1977 Huge Guns N Roses Fan

    272
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    Dec 1, 2014
    Nashville
    .035 will be ok from a quench standpoint. I'd check my p to v clearance either going the clay route or using a dial indicator. think as long as you're not below .070 on intake or .100 on exhaust then you're safe. best place to measure the one and the other are at 10deg BTDC and AFTDC.
     
  7. Mwilson

    Mwilson Veteran Member

    talked to the local engine builder ( builds nascar stuff ) he says I'm good he said he wouldn't be worried until .032, its together now!! lol 24831138_1942793072708007_3145345675222076419_o.jpg 24883571_1942765059377475_8616308329450163794_o.jpg
     
  8. Mwilson

    Mwilson Veteran Member

    pistons have a 1.140 compression height and I had .012 cut off the block
     
  9. muscl car

    muscl car Veteran Member Lifetime Gold Member

    Where's the idle / rev video ??
     
  10. Mwilson

    Mwilson Veteran Member

    intake not bolted down yet no silicone!! lol
     

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