Power/speed. 5.3 chevy help please

Discussion in 'Chevy Silverado Forum (GMC Sierra)' started by Tylert003, Apr 6, 2014.

  1. Bowtied

    Bowtied Epic Member 5+ Years 500 Posts

    wow, longer stroke as in a simple Rod swap or is there crank changes too? would it be a popular mod for the 4.8 guys to put longer Rods into their trucks to get a decent gain in displacement? ​

    99'HEARTBEAT MODERATOR Staff Member 5+ Years ROTM Winner 1000 Posts Platinum Contributor

  3. RayVoy

    RayVoy Epic Member 5+ Years 5000 Posts

    Nice find Mike

    One of the things that determines the compression ratio, is the combustion space when the piston is at top dead center (TDC).If what you want is to increase the compression ratio, removing some metal from the block decks will give you an increase (this effectively allows the top of the piston to get closer to the head, reducing the combustion volume). There are limits, the pistons can not touch the values when they are open.

    Applying this to going with a longer stroke, if we increase the distance the piston is pushed up the cylinder, we must be sure there is no possibly contact with the values.

    To ensure this, when the crank throw is lengthened, the rod must be shorter; therefore, the combination of a longer throw and a shorter rod should place the top of the piston in about the same place as the top of the piston was before the changes were made.

    So, what's the value of stroking an engine you ask? Well, when you lengthen the throw and shorten the rod, the combination will pull the piston farther into the cylinder. increasing the volume of air/fuel drawn into the cylinder on the intake stroke. This increased volume of mix is compressed into the same combustion space that the engine had before the mods. More fuel and air and a slight compression increase equals more power.
  4. Bowtied

    Bowtied Epic Member 5+ Years 500 Posts

    does it also equal more displacement? im wondering how they are gaining an additional .5 liter without changing bore, apparently by using shorter rods and dished pistons it appears from the article (although i only got thru half of it, admittedly)
  5. Rocketmanh5

    Rocketmanh5 Rockstar 100 Posts

    Depending on the year model of the engine being done. The main difference that makes up on what I mentioned is the flat top pistons. The shorter stroke also plays a good difference if your trying to get from point A to point B quicker. A longer stroked motor does well on the other end starting to pull later than the shorter stroked motor. The 5.3 and 4.8 are pretty much equal in power and weight for stock motors. The 5.3 does exceptionally well with just a cam swap (and of course better springs and all). Just from personal experience that the 4.8 is a nice piece to use if your wanting to go down the turbo road of things. Plus a 4.8 short block is pretty cheap compared to a 5.3 or 6.0 out of a salvage yard when your on a build budget. In relation to the LQ9 I purchased to go in a project '88 I wish I would have went on with a 4.8 and a small turbo and that would have made way more power than what I was trying to squeeze running 110 octane and head work.

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