make less power......
make less power...... Now for something different....Help me build a LS that makes LESS power!! LOL... OK, back story. I have a GT track car that is powered by a mild, but strong 5.3l “LS”. It makes 360 WHP for hours at a time running from 5500-6800RPM. It appears there is a rule change coming where cars will be classed based on peak HP and car weight. I will be clobbered with the current engine. What I need to do is reduce power to around 300WHP but with as much power “under the curve” as possible. In other words, as much power down low with a flat HP/torque curve as possible. I know tuning will have a large part in this, but I want to give the tuner a head start with hardware best suited for this.
· The current engine, and base for this build is as follows:
· Gen IV 5.3l aluminum block with a 3.898 bore
· Mahle pistons (10.6cr) with Scat “Sportsman” rods / factory 58x crank
· 243 heads with BTR Beehives
· Comp Cam 220/224 .568 112LSA (quite mild but easy on valve gear)
· LS1 intake with DBW TB and 32-38lbs injectors
· E38 ECU with HPTuners
I have 241 heads and I’m thinking the smaller ports “may” help here. Also, I understand the LS1 intake is horrible, but I can’t fit a truck intake.
What are the thoughts or suggestions here?? Tuning advice? Anyone built something like this?
As always, Thanks!
Gord.
· The current engine, and base for this build is as follows:
· Gen IV 5.3l aluminum block with a 3.898 bore
· Mahle pistons (10.6cr) with Scat “Sportsman” rods / factory 58x crank
· 243 heads with BTR Beehives
· Comp Cam 220/224 .568 112LSA (quite mild but easy on valve gear)
· LS1 intake with DBW TB and 32-38lbs injectors
· E38 ECU with HPTuners
I have 241 heads and I’m thinking the smaller ports “may” help here. Also, I understand the LS1 intake is horrible, but I can’t fit a truck intake.
What are the thoughts or suggestions here?? Tuning advice? Anyone built something like this?
As always, Thanks!
Gord.
On The Tree
Joined: Feb 2022
Posts: 196
Likes: 72
From: Grand Rapids, MI
I'm thinking a small intake or air filter. Choke it there, and reduce rpm to 5800.
Or limit throttle blade to 75% or so.
If you limit air coming in, it will still have enough air for torque down low but wont flow up top, giving you the desired result.
Good thing about v8s is they make lots of torque even at 2500rpm so you have a very large powerband.
Or limit throttle blade to 75% or so.
If you limit air coming in, it will still have enough air for torque down low but wont flow up top, giving you the desired result.
Good thing about v8s is they make lots of torque even at 2500rpm so you have a very large powerband.
On The Tree
Joined: Nov 2023
Posts: 107
Likes: 139
From: South of sweden
Interesting as i'm going to do the same thing on a LSA.
My goal is 380-400 crank HP to get my car pass registration.
SC of and small throttle body as a start.
/Christian
My goal is 380-400 crank HP to get my car pass registration.
SC of and small throttle body as a start.
/Christian
Last edited by christianmoller; Nov 5, 2025 at 11:05 AM. Reason: too much numbers... :)
To me, it depends on how much power you’re trying to erase. You can severely limit power with ignition timing, and you can choose where in the powerband it gets limited. Another method would be to install a restrictor in the air intake track. Does the sanctioning body dyno you before and after every race, or is it a one time thing pre-season?
TECH Fanatic
Joined: Jul 2022
Posts: 1,019
Likes: 385
From: Alaska
I built ICE Racing engine:
Old first gen 350, flat top forged pistons, 62 cc aluminum heads and intentionally put in WAY TOO much cam ( Cheapest Summit 292/302 duration ) to allow it to run on 90 octane **** gas, and make almost no torque below 2800 RPM. Worked great with an undersize 600 CFM carb. Did not have hardly enough torque to spin tires out of corners, built power as it rev'd and was on step at end of straights. We ran it against the rev limiter for 10 years without issue.
Soft bottom end, and rev freely to 6500 many thousands of laps.
......Tiny Carb, and rev limiter at 5500 and gross Crank HP would end at about 325... Same engine with 750CFM at 6800 rpm makes 475 flywheel HP
Old first gen 350, flat top forged pistons, 62 cc aluminum heads and intentionally put in WAY TOO much cam ( Cheapest Summit 292/302 duration ) to allow it to run on 90 octane **** gas, and make almost no torque below 2800 RPM. Worked great with an undersize 600 CFM carb. Did not have hardly enough torque to spin tires out of corners, built power as it rev'd and was on step at end of straights. We ran it against the rev limiter for 10 years without issue.
Soft bottom end, and rev freely to 6500 many thousands of laps.
......Tiny Carb, and rev limiter at 5500 and gross Crank HP would end at about 325... Same engine with 750CFM at 6800 rpm makes 475 flywheel HP
Last edited by Full Power; Nov 5, 2025 at 06:56 PM.
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TECH Addict
Joined: Dec 2017
Posts: 2,166
Likes: 961
Exactly HOW are they going to know how much power your engine makes?
Kinda stuuupid to talk about how to reduce it if it's unknown how it's going to be measured.
That aside, I think the best way would be a smaller cam on a wider LSA, maybe advanced a bit from where it is now.
Kinda stuuupid to talk about how to reduce it if it's unknown how it's going to be measured.
That aside, I think the best way would be a smaller cam on a wider LSA, maybe advanced a bit from where it is now.
Last edited by RB04Av; Nov 6, 2025 at 11:44 AM.
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Staging Lane
Joined: Oct 2025
Posts: 89
Likes: 32
I would start with having multiple tunes for the car. Set up your spec race tune with a few degrees of timing taken out at WOT high rpm. That will back off your peak power. Will have no effect on the power curve down low.
Exactly HOW are they going to know how much power your engine makes?
Kinda stuuupid to talk about how to reduce it if it's unknown how it's going to be measured.
That aside, I think the best way would be a smaller cam on a wider LSA, maybe advanced a bit from where it is now.
Kinda stuuupid to talk about how to reduce it if it's unknown how it's going to be measured.
That aside, I think the best way would be a smaller cam on a wider LSA, maybe advanced a bit from where it is now.
To me, it depends on how much power you’re trying to erase. You can severely limit power with ignition timing, and you can choose where in the powerband it gets limited. Another method would be to install a restrictor in the air intake track. Does the sanctioning body dyno you before and after every race, or is it a one time thing pre-season?
TECH Addict
Joined: Dec 2017
Posts: 2,166
Likes: 961
If that's all it is, just make a restrictor plate out of like .020" stainless shim stock for behind the TB. Make a few different ones so you can pick the right size at the dyno. That'll let you keep your tune as aggressive as possible and won't require any mechanical changes.
Still, if you have to give up HP, might as well pick up some torque at slightly lower RPMs; maximize what's allowed. A cam change is the way to go for that. Step it down 6° or so on the intake and keep about the same split you have.
Still, if you have to give up HP, might as well pick up some torque at slightly lower RPMs; maximize what's allowed. A cam change is the way to go for that. Step it down 6° or so on the intake and keep about the same split you have.