Once again, another week is already nearing completion. That means Thursday has landed on our doorsteps. With the end of the week looming, are you making garage plans about what you need to accomplish this weekend? Or, have those plans already been made? If your weekend includes enjoying some garage time with your project include deciding which small-block Chevy heads you should use, you might want to check this out.

In this edition of Throwback Thursday, we’re taking a leap back to April 2015, to check out: GM 1st Gen Heads vs. Vortec Heads Reader Guide. When it comes to rebuilding the Gen I SBC engine, selecting the right combination of cylinder head for the block becomes the ultimate performance question. With many different varieties of Chevy heads available, and the newer Vortec cylinder heads now heavily in play, it’s difficult to always know what head is the right choice for home engine builders. We have some cylinder head information that might help clear the vision for your next Gen I SBC engine build.

The Gen I Chevy heads were developed when leaded fuel was used. The lead helped keep the valve seats lubricated. But, the Unleaded fuel that is available now, requires the valve seats be replaced with hardened valve-seat inserts or they wear very quickly.

The Vortec head (top) does not have the heat crossover that the Gen I cylinder heads have (bottom). Heat can be an issue with used Vortec heads.

Starting in 1996, on several GM trucks and vans, the L31 Vortec heads came on the scene. Thses new Chevy heads were not just a modified version of existing heads, but a complete redesign using the 1996 Caprice/Impala SS LT1 cast-iron head castings as a base.

In the original article it is explained that the biggest change in the new design was revising the water jacket so the new Vortec heads could be used on conventionally cooled small-blocks. The idea of using the 1996 LT1 cast iron head as a starting point for a new performance-minded stock head came from the fact it was the highest flowing LT head used by GM.

Vortec heads have the “sawtooth” pattern casting mark on the end of the heads.

There is a lot more information in the original article, and you’re sure to find out everything you want to know. That’s why I chose GM 1st Gen Heads vs. Vortec Heads Reader Guide as this week’s Throwback Thursday article.