Ls1 aluminum block boost limit
Thread Starter
Cruising
Joined: Aug 2024
Posts: 10
Likes: 1
Ls1 aluminum block boost limit
Hey everyone!
Im currently building a standard 400whp heads, cam, intake ls1, but I know once I get tired of that I’m going to end up going forced induction. I’ve been going back and forth between swapping in a 6.0 iron block due to its strength, or just keeping the stock ls1. I plan on doing forged internals so my only concern is the actual block strength. At what point do i literally crack the block? Im currently on a stock T-56 and i know once you start reaching the 5-600hp range, they starting blowing up, and im sure the ls1 is fine at that point, but I’d like to eventually go up to around 800 wheel. Is that feasible with a forged piston and rod ls1? Should I just go with an iron block for better reliability? Has anyone boosted a ls1 that high? Any help id appreciate!
Im currently building a standard 400whp heads, cam, intake ls1, but I know once I get tired of that I’m going to end up going forced induction. I’ve been going back and forth between swapping in a 6.0 iron block due to its strength, or just keeping the stock ls1. I plan on doing forged internals so my only concern is the actual block strength. At what point do i literally crack the block? Im currently on a stock T-56 and i know once you start reaching the 5-600hp range, they starting blowing up, and im sure the ls1 is fine at that point, but I’d like to eventually go up to around 800 wheel. Is that feasible with a forged piston and rod ls1? Should I just go with an iron block for better reliability? Has anyone boosted a ls1 that high? Any help id appreciate!
Last edited by FairHairWarrior; Sep 16, 2024 at 02:42 PM. Reason: Misspelling
Racer
Joined: Nov 2017
Posts: 449
Likes: 158
From: Aiken, SC
People have made 1000+ on an ls1 block. That being said, the sleeves are the weak point. If changing the block is an option, the best move is to find a gen 4 aluminum block. They will hold more power than you can use on the street and you aren't adding the ~110 lbs of an iron block
Race Director
Joined: Dec 1999
Posts: 10,230
Likes: 885
From: Alexandria, Virginia, USA VA
stay with alum block and make sure you tune it well
I ran 800 at the tire for years with ttix and ls6 block (weaker still due to bottom end breathing)
going to 5.3 alum block for more power
I would use ls1 up to 1k hp at engine which is more than drivetrain can manage😍😍
using huron TT and and pair of 67s on next build
I ran 800 at the tire for years with ttix and ls6 block (weaker still due to bottom end breathing)
going to 5.3 alum block for more power
I would use ls1 up to 1k hp at engine which is more than drivetrain can manage😍😍
using huron TT and and pair of 67s on next build
Pro
Joined: Feb 2005
Posts: 652
Likes: 16
From: Upton MA
I beleive an LS1 block will hold 800 WHP. I would not go higher. Given you are going to forged parts, now is the time to decide on compression ratio based on wether it is n/a or F/I. I have an RHS 7.0 liter block and I run 9.0 c/r. I have a D1X and use 93 octane with a small amount of 100% meth about +1/2 A/F point @ 21 psi 1000 rwhp 880 rwtq.
Supporting Vendor
Joined: Apr 2012
Posts: 2,674
Likes: 370
From: Forney TX
People have made 1000+ on an ls1 block. That being said, the sleeves are the weak point. If changing the block is an option, the best move is to find a gen 4 aluminum block. They will hold more power than you can use on the street and you aren't adding the ~110 lbs of an iron block
Supporting Vendor
Joined: Apr 2012
Posts: 2,674
Likes: 370
From: Forney TX
Hey everyone!
Im currently building a standard 400whp heads, cam, intake ls1, but I know once I get tired of that I’m going to end up going forced induction. I’ve been going back and forth between swapping in a 6.0 iron block due to its strength, or just keeping the stock ls1. I plan on doing forged internals so my only concern is the actual block strength. At what point do i literally crack the block? Im currently on a stock T-56 and i know once you start reaching the 5-600hp range, they starting blowing up, and im sure the ls1 is fine at that point, but I’d like to eventually go up to around 800 wheel. Is that feasible with a forged piston and rod ls1? Should I just go with an iron block for better reliability? Has anyone boosted a ls1 that high? Any help id appreciate!
Im currently building a standard 400whp heads, cam, intake ls1, but I know once I get tired of that I’m going to end up going forced induction. I’ve been going back and forth between swapping in a 6.0 iron block due to its strength, or just keeping the stock ls1. I plan on doing forged internals so my only concern is the actual block strength. At what point do i literally crack the block? Im currently on a stock T-56 and i know once you start reaching the 5-600hp range, they starting blowing up, and im sure the ls1 is fine at that point, but I’d like to eventually go up to around 800 wheel. Is that feasible with a forged piston and rod ls1? Should I just go with an iron block for better reliability? Has anyone boosted a ls1 that high? Any help id appreciate!
Melting Slicks
Joined: Mar 2006
Posts: 2,754
Likes: 380
From: South Florida FL
If you're building a street car, there's many other limitations you'll run into for the Aluminum block is your problem. personally I'm not stepping into an iron block unless I intend to make over 1200-1300whp. But you should break everything else in the drivetrain and sell your car, before you're splitting blocks.
Thread Starter
Cruising
Joined: Aug 2024
Posts: 10
Likes: 1
Awesome, all great info. One more question: someone brought up compression ratio earlier. Since I’m replacing most of the rotating assembly, I’ll be able to up compression if I want. I know you typically don’t want to boost compression too high when you’re going forced induction but would there be significant benefit in doing so? I was planning on just going with a piston that keeps the same combustion chamber volume but if it would be worth it to go with anything higher compression, ill go that route. Any thoughts? Also, I plan on running e85 if that changes anything
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Race Director
Joined: Dec 1999
Posts: 10,230
Likes: 885
From: Alexandria, Virginia, USA VA
e85 compression
I wouldn't be afraid of 10o 10.5 to 1 on e85 even with boost
it will make the car much more responsive too
e85 has much more forgiving characteristics and is the "boost juice"!
it will make the car much more responsive too
e85 has much more forgiving characteristics and is the "boost juice"!
Le Mans Master
Joined: Oct 2010
Posts: 7,373
Likes: 1,128
From: cold & windy
i'm running 10.6 SCR on mine with 13psi from a roots blower... but that's also with a big cam that puts my DCR a little lower than stock.
it's ultimately about controlling overall cylinder pressure, temperature, and air density. the more boost you're pushing, the lower you'll want your compression ratio so as to not super-heat the combustion charge to the point of pre-detonation (knock). gas vs ethanol plays a role in that decision (and directs your fuel pump/injector setup).
higher compression will maintain responsiveness and efficiency during part-throttle driving, but it gives you a smaller tuning margin for bad gas, high IATs, etc.
lower compression makes tuning easier/safer but also feels more sluggish until you get into boost.
it's ultimately about controlling overall cylinder pressure, temperature, and air density. the more boost you're pushing, the lower you'll want your compression ratio so as to not super-heat the combustion charge to the point of pre-detonation (knock). gas vs ethanol plays a role in that decision (and directs your fuel pump/injector setup).
higher compression will maintain responsiveness and efficiency during part-throttle driving, but it gives you a smaller tuning margin for bad gas, high IATs, etc.
lower compression makes tuning easier/safer but also feels more sluggish until you get into boost.
Last edited by _zebra; Oct 11, 2024 at 12:54 PM.
Le Mans Master
Joined: Oct 2010
Posts: 7,373
Likes: 1,128
From: cold & windy
i also wouldn't look at "boost" as a block limitation - unless you're talking about lifting 4-bolt heads at 20+psi or something.
it's more of a power production thing than an airflow restriction limit. i'd also consider RPM as a factor because i sure wouldn't want to push 15psi @ 1500rpm (which my TVS could do)... that's asking to turn my bottom end into piñata candy.
it's more of a power production thing than an airflow restriction limit. i'd also consider RPM as a factor because i sure wouldn't want to push 15psi @ 1500rpm (which my TVS could do)... that's asking to turn my bottom end into piñata candy.