Reduce LS3 Horsepower
Thread Starter
Teching In
Joined: Dec 2023
Posts: 46
Likes: 7
Reduce LS3 Horsepower Hi,
I've got a 416 LS3 road race motor with TSP Brawler heads, custom cam and Pro Systems 4 barrel carb. It is about 12:1 compression. I tuned it on a chassis dyno and got the following peak horsepower numbers at different timing advance settings:
* 24 degrees - 534 HP
* 28 degrees - 552 HP
* 30 degrees - 565 HP
I want to detune the motor down to about 460 HP. This is for reusing the motor in a different road racing application ... so that would be taking about 75 horsepower out if it when it was running 24 degrees.
What's the best way to go about that? Can I keep taking timing out? All the discussions on here are about max timing you can put into a motor to balance detonation and octane requirements. But I am not aware of any downsides to taking too much timing out or if there is a floor to how low you can go.
Also considering putting in a carb restrictor plate. The carb has 1.75" bores so I can go down to 1.5 or 1.2, etc.
Or maybe a mix of timing and restrictor plate.
Thoughts?
I've got a 416 LS3 road race motor with TSP Brawler heads, custom cam and Pro Systems 4 barrel carb. It is about 12:1 compression. I tuned it on a chassis dyno and got the following peak horsepower numbers at different timing advance settings:
* 24 degrees - 534 HP
* 28 degrees - 552 HP
* 30 degrees - 565 HP
I want to detune the motor down to about 460 HP. This is for reusing the motor in a different road racing application ... so that would be taking about 75 horsepower out if it when it was running 24 degrees.
What's the best way to go about that? Can I keep taking timing out? All the discussions on here are about max timing you can put into a motor to balance detonation and octane requirements. But I am not aware of any downsides to taking too much timing out or if there is a floor to how low you can go.
Also considering putting in a carb restrictor plate. The carb has 1.75" bores so I can go down to 1.5 or 1.2, etc.
Or maybe a mix of timing and restrictor plate.
Thoughts?
TECH Enthusiast
Joined: May 2008
Posts: 648
Likes: 580
From: Carnation, WA
If there is ducting to the carb, a restriction there might cause less turbulence in the intake. I’d try to do it all with restriction if possible, and avoid running excessively retarded timing.
Thread Starter
Teching In
Joined: Dec 2023
Posts: 46
Likes: 7
Thanks!
TECH Enthusiast
Joined: May 2008
Posts: 648
Likes: 580
From: Carnation, WA
When the EGTs start getting too hot …. Why burn fuel in your headers? Usually, power plateaus when you keep increasing timing. Run the minimum timing that gets you to the plateau. That gives you some knock margin.
Thread Starter
Teching In
Joined: Dec 2023
Posts: 46
Likes: 7
Gotcha. Run the right timing to keep the motor in the healthy/happy state and restrict the airflow. That makes sense. Thanks!
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A restrictor plate is a good idea, but it will feel “boggy” unless you cam for the plate. I’d try a 500 cfm 2 barrel race carb and play with timing. I happen to have a high end 500 cfm carb, built by Jeff (RIP) at Up Front in Cornelia Ga. that I’ve never bolted on an engine…leftover from my pavement late model days.
F
RD!!