GAPPING your piston rings is a relatively cheap and easy way of keeping your budget build from munching itself. It’s a known fix for junkyard LS builds to keep them happy under heavy boost, but it was unclear if it’s a worthwhile precaution to take with a Barra.
While we were in the process of tearing apart the bottom end of yet another LPG Barra for our Turbo Taxi Carnage project (actually the matching-numbers engine!), we decided to do some home-brewed investigation to see what’s what.
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What Scotty found was that the top rings in particular are quite tight in factory spec – 18thou for those playing at home. While that may be fine for a stock donk on standard power, we figure the risk of that ring crying ‘enough!’ when we shove more than 25psi down its throat is fairly high.
The reason for gapping rings is a fairly simple one. Taking an engine and doubling or even tripling the power levels the factory intended creates a lot of extra heat. That heat causes the rings to expand, sometimes far enough that the ring gap closes and causes all kinds of issues – how does ripping the top of the piston off sound?
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Needless to say, we’ll be carefully checking our ring gaps when we throw this donk back together for the Taxi, so make sure you keep an eye out for that!