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Recently, Steve Morris released a video where he built a big-bore 5.3L block using a billet deck plate in order to create a big-bore, dry-deck block. That video pulled back the curtain on Morris’ in-depth machining and rebuilding of the block, but also created some confusion on what is needed to run a big bore.
There are several companies that resleeve Gen IV blocks to accept big 4.125-plus-inch bores that don’t require a billet dry-deck conversion to accomplish the task, as BoostLine Performance shows in the above video. Where the confusion seems to lie is in the block that Morris worked on in his video, which is different than typical Gen IV 5.3L blocks. As Albert from BoostLine clarifies, “I think there’s some confusion on Steve Morris’ recent video. If you look at our Gen-IV blocks, they are a completely siamesed design. There is solid aluminum between the cylinders, even after our big-bore sleeves are installed.”
On the left, you can see what a siamesed Gen IV aluminum 5.3 block looks like. There's solid aluminum between the cylinders. On the right is a Gen IV FWD block (similar to the Gen III aluminum blocks) where there is an opening between the cylinders in order for water to pass through.
It’s known that the Gen III aluminum blocks are not siamesed, which makes them incapable of receiving the big-bore sleeves. Where the confusion appears to be happening, is with the front-wheel-drive Gen IV blocks. As Albert points out, he’s found that the front-wheel drive Gen IV aluminum blocks are like the Gen III blocks, resulting in the issues seen in Morris’ video, of breaking through the host block material while machining to size for the sleeve.
Typical aluminum 5.3L Gen IV blocks are siamesed, and as such are able to be resleeved with dry sleeves, allowing for a 4.125-inch-plus bore. Albert shows, in the video above, how they are machining the Gen IV blocks and fitting the Darton sleeves. “There’s nothing wrong with what [Steve Morris] is doing. We just have no need to ‘correct’ the issue like in Steve’s video, because we don’t have the issue,” he says.
“We have plenty of support on the sleeve, plenty of support on the shoulder of the sleeve for clamping load. We have no reason to mill the deck out of these blocks to get the bigger bore in them.” Really, what it comes down to, is that there are multiple ways to get the job done to hold big power, all of which have been proven to be effective. As an enthusiast, there’s never been a time with more reasonably priced big-bore aluminum block options.
On the left, you can see the block machined for the sleeves, prior to their installation, and on the right, You can see the installed Darton sleeves from BoostLine Performance.
