What's The Difference Between A GM 602 And 604 Crate Engine?

There is a huge number of crate engines to choose from out there, and while some crate engines will be perfect for big power builds, others are tailored to more specific needs. Both the GM 602 and 604 crate engines fall into the latter camp, having been specifically designed for circle track racing.

Circle track racing features heavily modified cars racing on dirt or clay-surfaced oval tracks. Despite the fact that there are differences between the GM 602 and 604 crate engines — namely, the cylinder heads, camshaft type, and valvetrain — both engines are designed for the same type of racing. Those aforementioned mechanical differences also mean that the outputs of both engines differ, with the GM 604 delivering slightly more power and torque than the 602 at different points in the rev range.

In addition to mechanical and output variations, another way these two crate engines differ is their specific target market. While both are for circle track racing, they are used by different classes. For example, the GM 602 is typically used in the IMCA Sport Mod and Hobby Stock classes, as well as some regional series like the Indiana Late Model Series and Crate Racin' USA. By way of contrast, the GM 604 is geared to compete within the IMCA Late Model and Modified classes, alongside a different set of regional series.

The differences don't stop there either. Comparing the exact specifications between these two engines reveals a wide range of smaller differences between the two. For example, the GM 602 uses Votrec cast iron heads, instead of the 604's "fast-burn" aluminum heads. The latter engine uses modifications like this, in addition to a higher compression ratio of 9.7:1 (compared to the 602's 9.1:1) to produce more output.

Specifically, the GM 604 crate engine is rated for 404 horsepower, which arrives at 5,600 rpm, while it hits its peak torque of 406 lb-ft at 4,600 rpm. Conversely, the GM 602 produces slightly less of both, with its 350 horses arriving at 5,400 rpm, and 396 lb-ft of torque doing so at 3,800 rpm. The GM 604 is the peakier engine, with power and torque both arriving higher up in the rev range. A final differentiator would be the price of these two. While neither is amongst the cheapest V8 crate engines on the market, the GM 602 is the more budget-oriented. Outlets typically sell the 602 for between $7,300 and $8,000, whereas the 604 commands more in the region of $8,900 to $10,000.