What is the difference between the TS, ST, and 2.3L cylinder blocks?

The TS, ST, and 2.3 blocks all share the same bore (87.5 mm) and deck height (231 mm). Because of this, we can change cranks and rods to to obtain either a 2.0 L or 2.3 L displacement without any boring of the block. But there are many things to consider when choosing the correct block for your setup and we will outline some of these below. 

The blocks themselves vary slightly in the following ways:

1. The ST block, shown in Figure 1, is a closed deck block and has a cast in water pump housing. It has all the mounting holes for FWD engine mounts, but is missing 2 holes on the passenger side for RWD engine mounts. Because of this, the ST block requires a custom engine mount for use in RWD applications. The casting method for the ST block is visually different from that used on the 2.3 block and the ST block has a considerably more external bracing on the exterior of the block near the bottom of the head bolt bosses. These blocks seem to be capable of supporting 600-700 whp with the proper tuning and mods, and requires the use of the ST gasket and head unless oil ports are blocked off.

Figure 1: Above is a picture of the ST cylinder-block. It is easily identified by the closed deck design and its cylinder-indpenedent coolant jackets.

2. The TS block is semi-closed deck, as shown in Figure 2, and also has a cast in water pump housing. It has all the mounting holes for FWD engine mounts, but is missing 1 bolt hole on the passenger side for RWD engine mounts. This allows the use of this block in RWD applications using the OEM engine mounts. The casting method for TS block is similar to the ST block, but doesn’t have as much external bracing on the exterior of the block on the exhaust side. These blocks seem to be able to handle 500-600 hp with proper tuning and mods, and it is recommended to use the RS gasket with the twin scroll head on these blocks. 

Figure 2: The TS cylinder-block is shown above. The TS block is identified by its semi-closed deck and the shared coolant jackets between cylinders. 

3. The 2.3 block, displayed in Figure 3, is an open deck block and has a bolt-on water pump housing. This distinguishes the 2.3 block from the others and can lead to confusion when swapping to the ST or TS blocks. Many think the ST or TS requires a different water pump, but that is not the case. The 2.3 water pump fits the ST and TS perfectly, but must be removed from the bolt on housing by removing three M6 fasteners (Figure 4). The 2.3 block also has all mouting holes for FWD and RWD engine mounts. The 2.3 block lacks support under the head bolt bosses and is prone to cracking the block at 450-550 whp, however, more hp has been achieved on this block on rare occasions. It is also recommended to use the RS gasket with the twin scroll head on these blocks.

Figure 3: The 2.3 block, as comes in the Mustang and RS, is shown in the picture above. The 2.3 is readily identified by is opened deck design that shares a large coolant reservoir around all cylinders.  

Figure 4: The water pump (highlighted in blue) should be removed from the bolt-on water pump housing of the 2.3 and transferred to the ST or TS blocks as-cast water pump housing. 

We always get asked “which blocks will crack” and the short answer is all of them, but the TS and ST blocks are much more resilient than the 2.3 block. With big power comes big risks, and it only takes a few tenths of a second with no octane, lean, etc for any of these blocks to crack, but the difference is with the 2.3 a crack can occur at any time past 500 hp, whereas, the ST and TS blocks won’t crack unless there is an “event” (e.g., not bleeding a meth line, moon boost and running lean, pump gas on e85 tune, aux kit turns off, etc).