Summary

How critical are torque plates when having a block bored? Really depends on the particular engine block you're dealing with. Some will distort more than others, so for those who aren't aware a torque plate bolts to the engine block during the boring and honing process, and it replicates the distortion that will be present in the bores when the cylinder head is bolted on.

00:00 - John has asked, how critical are torque plates when having a block bored? Really depends on the particular engine block you're dealing with.
00:07 Some will distort more than others, so for those who aren't aware a torque plate bolts to the engine block during the boring and honing process, and it replicates the distortion that will be present in the bores when the cylinder head is bolted on.
00:23 So what we're trying to do here is make sure that in operation the cylinder bores are as round as possible and this gives us the best chance of getting a good ring seal.
00:32 So some blocks as I've sort of mentioned, will distort more when the head is bolted down than others.
00:39 And I can't really tell you exactly which blocks where this is essential, which blocks we would require this and which blocks we don't.
00:46 As a matter of course, every engine that we build, we torque plate bore and hone.
00:50 And that gives us the best chance of getting the best possible result.
00:54 What we do find though is that in some blocks, the stud holes for the head studs or the head bolts are completely separate from the engine liner.
01:06 So that's actually the case here, if we can just go to our overhead camera for a second, so with our Subaru FA20 engine, this is called an open deck block design.
01:14 So we see that the actual sleeves are completely independent to the outside of the block and our bolts holes for our cylinder heads are not connected to the actual sleeves themselves.
01:26 So with a block design like that, typically we won't see as much distortion in the bores when the head's torqued down, compared to a block where the bolt holes are actually sort of connected to the sleeve itself.
01:41 So again every block is slightly different there.
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