Chevy’s Vortec heads from the late ’90s are a little secret weapon – Jalopnik

Any engine builder will tell you how important cylinder heads are to power and performance, so enthusiasts looking to freshen up their budget Chevy 305 small-block (SBC), or the larger and more popular 350, should find GM’s Vortec heads a worthwhile investment.

Knowledgeable people often claim that these cast iron Vortec heads from the 90’s are the best flowing SBC head design from the factory. The argument is supported by actual flow figures Hemmings Comparison shows that Vortec heads improve intake flow by up to 30 CFM (cubic feet per minute) during maximum lift.

Unsurprisingly, the improved flow properties allow the engine to breathe better and unleash more power, as evidenced by MotorTrend Getting an extra 50 horsepower from a ZZ4 small-block after bolting on a pair of stock Vortec heads. Other benefits, compared to a standard small-block head, include improved engine efficiency, thanks to the Vortec heads’ ability to use a higher compression ratio.

Many small blocks from the 1960s with flat top pistons and 76 cc combustion chambers are often clocked at 8.5:1 compression, which, when replaced with Vortec heads using 64 cc chambers, see their compression ratio increase to 9.8:1, resulting in better efficiency and a 5% increase in horsepower.

Before you decide on these budget Vortecs, there are a number of things you should take into account, starting with the intake manifold. GM decided to change the Vortec’s bolt pattern from the small block’s traditional six-bolt pattern to four per side, meaning the intake manifold is now an eight-bolt setup. The bolt size and layout are also different. Another thing to note is that using Vortec heads requires the use of center bolt type valve covers and Vortec specific gaskets, which may or may not be a pain depending on who you ask.

Cracks aren’t uncommon on these either, especially since they date from the late 1990s, a time when Chevy had some unique pickup trucks in its lineup. You can of course buy these heads refurbished or brand new as aftermarket support is quite extensive. In today’s sea of ​​high-quality aluminum heads, these modest cast-iron Vortecs seem undervalued and perhaps deserve a closer look.