Forcefed86

iTrader: (4)

Do these all have the same flat top pistons in them? Trying to understand the compression differences between them. I've heard the L20 might have valve reliefs in the pistons? but I can't seem to confirm that online?

Compression is listed as...

LY2 - 9.1:1
L20 - 8.8:1

If the only difference is the 61.15cc head VS the 64.45cc head? Do the use the same pistons, blocks, rods, head gaskets etc? So 3.3cc of CC is only dropping compression .3?

tech@WS6store

iTrader: (2)

L20 has vvt ly2 doesnt so prob the vvt reliefs on the pistons.
L20 is flex fuel also.

Forcefed86

iTrader: (4)

Looks like it. heres a 2010 4.8 piston.

JoeNova

The LY2 has 243/799 heads and doesn't have either DoD or VVT.
The L20 has VVT.

SeanAllen

My 2013 L20 has valve reliefs and 799 heads

tech@WS6store

iTrader: (2)

On gen4 4.8/5.3 i have not seen any other head besides 799 on them.

JoeNova

There was an early Gen 4 5.3 that stuck to the 862 heads. I can't remember the code off the top of my head but it was primarily used in vans and some trucks, and had an old style truck intake on it still.

Every gen 4 4.8/5.3 with flat tops came with 799/243s

G Atsma

And that's a GOOD thing!

shrapnel

Both heads on my Gen4 5.3 (LY5) are 243s with the triangle marks. I specify both heads because I have heard some motors came with a 243 head on one side and a 799 on the other.

TrickFlowTech

If you have access to both for the same money, The L20 intake pockets will allow you more cam and the injectors flow more as well. Only downside is a bit of added cost for the VVT delete (depending on what you're doing).

07NBSChevy

iTrader: (1)

These specs are for the Silverado LY2 and L20 only, the Express/Savana engines may differ slightly. Both use 799/243 heads.
The Engines are identical- Block/Heads/Intake Manifold/Crankshaft/Connecting Rods/Piston Rings, with the exception of;
-Pistons (for VVT)
-The cam (for VVT)
-Timing cover (for VVT)
-Cam sprocket (for VVT)
-Intake valves (for E85 Flex Fuel)
-Valve covers (Older design was used on LY2)
-Oil filler neck
-Oil pan (different shape, same capacity of 6 qts.)
-Injectors for flex fuel.
-MAF Sensors, Airbox, and Intake tube (MAF Sensor location changed)

2007.5-2009 Silverado LY2 4.8L
-No VVT
-9.1:1 Compression using 0cc Flat Top Pistons
-295-Hp at 5,600 rpm, and 305-Tq at 4,600 rpm


2010-2013 Silverado L20 4.8L
-Has VVT
-Flex Fuel Capable
-8.8:1 Compression. The lower compression, compared to the LY2, is due to the added valve reliefs cut into the pistons for the VVT using -3cc Flat Top Pistons
-302-Hp at 5,600 rpm, and 305-Tq at 4,600 rpm.

Thought I what list all the differences in the two engines just in case, and yes...the valve reliefs are the only reason for the compression difference.

G Atsma

WHOA! You have done some serious homework, again! Good info! And THANKS!