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PostPosted: Sun May 25, 2008 1:56 pm 
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Retired Gearhead
Retired Gearhead
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Joined: Mon May 19, 2008 2:14 pm
Posts: 4753
Location: Orlando Fl
Year and Trim: '00 SSEi (proj), '99 Tahoe & '05 Bonne GXP
The L27 (1992-1994 (Bonneville), 1995 (U-bodies, Buick LeSabre) and the Series 1 L67 (1992-1995 Bonneville) both share the same ancestor, the LN3, and just by looking at the longblocks, one would be hard pressed trying to determine what engine was what. But this guide should show you just what those differences were.

First, let's look at the similarities. Both the L27 and the L67 use the same block,camshaft, crank, heads, exhaust manifolds, flywheels, and EGR systems. Timing covers are the same as well. In reality, there is nothing to externally differentiate the long or short blocks of the two engines...with the sole exception of the harmonic balancer. L67s use a two-belt balancer, the L27 is a single-belt design. If the timing cover and oil filter adapter is in place, you can tell the blocks apart that way as well...the L67 uses an oil filter adapter that allows an external oil cooler to be added...L27s did not get this option, but if one were to find this type of cooler in a junkyard, it could easily be fitted to an L27.

Now, for internal differences. THIS is where one can expect to see the most changes. The piston design is different between the two engine models in that the pistons and rods in the L67 use a floating-pin design, whereas the L27 uses a pressed-in pin. The piston crowns of the L67 are also coated in an ablative material...presumably to aid in the reduction of KR. Also, the piston rings are set slightly lower in the L67 for better protection from knock. The pistons and rods are heavier in design to allow them to survive boost. And the bearings...main, camshaft, and rod bearings...are made of a harder alloy for longevity.

On a side note, the 1992 model year saw both the L27 and the L67 use a rocker-pivot design, muck like the LN3 they replaced. Starting in 1993, the L27 and L67 received redesigned heads, and the L27 got new roller-pivot rockers...the L67 soldiered on with the old style pivot-rockers, but can have the roller-pivots swapped in as an upgrade (NOTE that this cannot be done with 1992-spec heads). 1994 saw the roller-pivot rockers on all models.

_________________
2005 GXP - White Gold Pearl, no mods...yet.
2000 SSEi - Resurrection in progress. Built L67 w/L32 fuel rail, ported heads, and cam. Camaro front brake system, GXP cluster, and much more in planning.

BonneMe wrote:
Looks like a Volt, Sonata, and Taurus got it on.


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