Block Guards

Block Guards: cylinder support for high-boost and high-rpm builds

A block guard is a machined insert that drops into the open-deck water jacket around your cylinder bores. Its job is to tie the top of the cylinders back to the block deck so the bores don't walk or flex under boost and heavy cylinder pressure. On open-deck aluminum blocks, that flex is what leads to head gasket failure and lost ring seal, and a block guard is the common fix builders reach for when a stock deck isn't holding up. It's a support piece, not a power part on its own - it lets the rest of your build survive the load. That's why block guards show up on turbo and high-rpm engine plans.

What ThreePiece stocks

There are 14 block guards in stock here, from two brands: Supertech with 11 of the products, and BLOX Racing with 3. Current pricing runs from $119 to $284 for what's on the shelf - that's the live range, not a fixed price. Guards in the range are cut for specific engines: examples include the BLOX Racing guard for Honda B16A / B18C DOHC VTEC, the Supertech guard for the Subaru EJ20 (two per engine), and the Supertech VQ35DET guard listed above. Engine families named across the range cover Honda, Nissan and Subaru.

How to choose

Block guards are engine-specific, so the first filter is your exact block - a B-series guard will not fit a VQ, and some engines take more than one piece per motor, like the EJ20 guard sold two per engine and the VQ35DET listed for left and right sides. Check the part description against your block before ordering. Beyond fitment, the price spread here mostly tracks how much material and machining the design involves; the Honda-family BLOX pieces sit near the bottom around $119-$123, while the multi-piece Nissan and Subaru Supertech sets run higher. Buy the guard that matches your block and your power target - there's no benefit to a heavier design if it doesn't fit your deck.

What else you need with it

A block guard goes in during a bottom-end or full engine rebuild, so plan for the parts you disturb getting there. You'll want fresh head gaskets or a full gasket kit on reassembly, and if you're already this deep it's the time to look at pistons and bearings. High-boost builds also lean on cooling and fuel, so check radiators and fuel pumps while you're spec'ing the combo. All of these sit under the wider Engine Components section.

Fitment help and ordering

Only some listings carry detailed vehicle fitment data, so if you're unsure whether a guard matches your block, call fitment help at 813-535-5801 or use the contact page before you buy. Every order ships free, and Affirm and Katapult financing is available if you're building in stages - details on the financing page.

Block Guards: cylinder support for high-boost and high-rpm builds

A block guard is a machined insert that drops into the open-deck water jacket around your cylinder bores. Its job is to tie the top of the cylinders back to the block deck so the bores don't walk or flex under boost and heavy cylinder pressure. On open-deck aluminum blocks, that flex is what leads to head gasket failure and lost ring seal, and a block guard is the common fix builders reach for when a stock deck isn't holding up. It's a support piece, not a power part on its own - it lets the rest of your build survive the load. That's why block guards show up on turbo and high-rpm engine plans.

What ThreePiece stocks

There are 14 block guards in stock here, from two brands: Supertech with 11 of the products, and BLOX Racing with 3. Current pricing runs from $119 to $284 for what's on the shelf - that's the live range, not a fixed price. Guards in the range are cut for specific engines: examples include the BLOX Racing guard for Honda B16A / B18C DOHC VTEC, the Supertech guard for the Subaru EJ20 (two per engine), and the Supertech VQ35DET guard listed above. Engine families named across the range cover Honda, Nissan and Subaru.

How to choose

Block guards are engine-specific, so the first filter is your exact block - a B-series guard will not fit a VQ, and some engines take more than one piece per motor, like the EJ20 guard sold two per engine and the VQ35DET listed for left and right sides. Check the part description against your block before ordering. Beyond fitment, the price spread here mostly tracks how much material and machining the design involves; the Honda-family BLOX pieces sit near the bottom around $119-$123, while the multi-piece Nissan and Subaru Supertech sets run higher. Buy the guard that matches your block and your power target - there's no benefit to a heavier design if it doesn't fit your deck.

What else you need with it

A block guard goes in during a bottom-end or full engine rebuild, so plan for the parts you disturb getting there. You'll want fresh head gaskets or a full gasket kit on reassembly, and if you're already this deep it's the time to look at pistons and bearings. High-boost builds also lean on cooling and fuel, so check radiators and fuel pumps while you're spec'ing the combo. All of these sit under the wider Engine Components section.

Fitment help and ordering

Only some listings carry detailed vehicle fitment data, so if you're unsure whether a guard matches your block, call fitment help at 813-535-5801 or use the contact page before you buy. Every order ships free, and Affirm and Katapult financing is available if you're building in stages - details on the financing page.