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p30 vs pr4 compression


p30 vs pr4 compression

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    p30 vs pr4 compression

    im doing some research on pistons i could use that are fairly cheap and easy to obtain by either on forums or craigslist.

    I decided to build on a spare b18a1 motor i bought for $100 head and block and some sensores but its pretty much bare.
    Ive heard of people replacing the stock pr4 pistons for the b16 pr3 or p30 pistons. im trying to see if its due to a increase in compression or just the simple fact that it fits..
    i looked up some picks for a comparisson and found the p30's have a bump in the center vs the pr4 have a collapsed center..

    so do the b16 pistons give a bump in compression or not? and by how much.

    true or false: You can add b16/p30 pistons on a ls block with no mods, just plug and play.
    BUT you can not use ITR or CTR pistons on a b18 ls block with out milling 2mm from the rods.. So when people say im going with b16 pistons or itr pistons someone please educate them.

    p30 piston

    pr4 piston
    half twisted
    Inactive Member
    Last edited by half twisted; 30 Jul 2009, 08:05:57. Reason: added my true or false note.


    Its that the b16 pistons fit on LS RODS just fine, but b18C pistons (P72, P73) do not without the milling. Both b16's and b18's come with an 81mm bore so peg in a hole wise they all fit.


      is there any draw backs i might run into due to high compression..
      with my ls and p30 pistons 81mm im looking at a lil under 11.00 10.98 to be exact..
      any smog issues...
      i plan on doing the skunk2 intake manifold and blox 68mm t/b. headers. maybe the carb legal skunk2 cams.


        when you get to that high comp. you have to start thinking about fuel/air ratio. making sure your not running to rich or lean. and using the right gas. becuase if your run into detination- then its lights out for your car

        but with proper fuel management and timing. all is good. Im actually looking for some p30 pistons.

        may I ask where you bought yours from. Im trying to find the best price


          I actually found out about it at a car meet. everyone there is always building something, selling or buying something. So I told my buddies to keep an eye out for me on a used b18a1 and sure enough a regular had a spare motor after swaping a b20... had it in storage for 3months so i offered him $100 and picked it up. if you need a motor ill ask around and post it up on the forsale.. same dude was selling a ls b18 with euc, harness, tranny, intke, ignition and everything needed for a drop in swap for $350. let me find out if its still for sale..