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I have a simple question, does the stock front vent bleed the air out of the heads just fine and putting a four corner aftermarket vent just eye candy?
I'm sure a lot of people will opt for the four corners as they feel this will keep the back cylinders cooler and avoid having air trapped inside the cylinder heads. GM did away with the four corners steam lines and plugged the back ones off and kept the fronts connected together and to the radiator. The engines tilt back anyways and the back of the heads are lower then the front so all air should make its way to the front once you've purged it of all the air. If your building a serious racer then why not run the four corner steam kit if for anything peace of mind alone.
For an engine that sees little to no high performance use the factory two fronts are probably just perfectly fine. A lot of folks don't worry about it and say to hell with the rear vents to save a few dollars.
The old Small Block Chevy doesn't have any fancy steam vent lines stock. However, the first serious SBC I had built the engine builder absolutely insisted on doing this to the Dart intake manifold. He was a firm believer in making sure no air/steam pockets get trapped in the cylinder heads.
"Stone Age" SBC gets high performance version of rear cylinder head air pocket & steam venting in stainless steel.
I would vent all four corners on any LS build, the old LS1 steam vent line can even be used in some cases. The aftermarket kits are fairly inexpensive too.
Cylinder #7 & #8 will probably be happier over the long run even in a daily driver.
03-12-2019, 07:21 PM
Steam vent - LQ4 - OE vs aftermarket 4 corner vent 
