Boostline performance
Teching In
Joined: Jul 2024
Posts: 13
Likes: 6
I plan on giving them a shot here in a month or so. One of their "big bore sleeved aluminum blocks" - https://www.boostlineperformance.com...s-engine-block
The only other good options I saw online are the two finished LSX blocks available in the 2026 GM Performance catalog. While the intro to the LSX blocks in the catalog says they leave dimensions for the builder, as in semi finished decks and bores.., if you look closely through the parts listings, they do offer two that are fully machined (finished deck, honed bore, align line honed mains, ect) ready for assembly.
Finished 4.185 bore (lsx454 block) part #19417353
Finished 4.065 bore (lsx376 block) part #19417352
After looking through the gm performance catalog for the regular LS/LT/ blocks.....actually I am pretty sure those are all finished and fully ready to assemble as well.
To me though I want to build one with a 4'' stroke and have good piston support at the bottom of the stroke. So besides the LSX blocks, the only other option is a resleeved block like the Boostline Performance big bore.
Here is the GM Performance catalog for 2026
https://indd.adobe.com/view/a055533b...b-5a4162877ac0
The only other good options I saw online are the two finished LSX blocks available in the 2026 GM Performance catalog. While the intro to the LSX blocks in the catalog says they leave dimensions for the builder, as in semi finished decks and bores.., if you look closely through the parts listings, they do offer two that are fully machined (finished deck, honed bore, align line honed mains, ect) ready for assembly.
Finished 4.185 bore (lsx454 block) part #19417353
Finished 4.065 bore (lsx376 block) part #19417352
After looking through the gm performance catalog for the regular LS/LT/ blocks.....actually I am pretty sure those are all finished and fully ready to assemble as well.
To me though I want to build one with a 4'' stroke and have good piston support at the bottom of the stroke. So besides the LSX blocks, the only other option is a resleeved block like the Boostline Performance big bore.
Here is the GM Performance catalog for 2026
https://indd.adobe.com/view/a055533b...b-5a4162877ac0
Last edited by etextown; Jan 27, 2026 at 04:57 PM.
Never heard of anyone using one of these blocks, but that’s a very good price, if I do say so myself. Final honed and cam bearings included. If the bores are square, it’s a viable option. If you purchase one, report back and let us know how it turns out with a few miles on it.
If you are going to beat the hell out of it I'd run as little bore as possible to keep the cylinder thicker. You should be able to get 0.005-0.010" shelf pistons also if the bores are ok to start unless 0.030" is all they offer for cores.
The Darton aftermarket sleeves have a lot of beef in them. 4.155” is max recommended bore for boost builds, and 4.185” is max NA recommended bore size although I’ve seen many guys go 4.195” for NA a builds. There’s plenty of sleeve left there for strength at 4.195”…the problem is with headgasket. You don’t have very much at all between the cylinders to seal. The ductile iron is much more resilient than cast iron bores from a performance standpoint. In my opinion, cast iron is the junkiest, crappiest, cheapest junk metal ever made for an engine material. I gladly welcome ductile iron Darton sleeves. It might be more brittle, but it’s so much more harder and robust than cast and can handle cylinder pressures while staying more round than cast.
