What limits RPM?
Thread Starter
Launching!
Joined: Sep 2008
Posts: 222
Likes: 46
From: Dayton, OH
Comp Cams recommends this spring kit, 26926TS-kit spring kit. Have to see what's in there when I pull the valve covers.
I will up the boost but not before forging the rotating assembly.
TECH Fanatic
Joined: Dec 2019
Posts: 1,129
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Have a cam I like. Posted the cam card a few posts ago. Keeping the rockers. I like the rockers. The trunnions have already been done. Just don't know what the springs are.
Comp Cams recommends this spring kit, 26926TS-kit spring kit. Have to see what's in there when I pull the valve covers.
I will up the boost but not before forging the rotating assembly.
Comp Cams recommends this spring kit, 26926TS-kit spring kit. Have to see what's in there when I pull the valve covers.
I will up the boost but not before forging the rotating assembly.
I've ridden 7600 RPM for 15+ seconds on high boost with stock: rockers/trunions/pushrods/valves/retainers/lifters/timing chain/pistons/rods/rod bolts.... basically everything stock except cam/springs.
Your gen 4 bottom end is stronger than my gen 3 bottom end. Don't stress too much over upgrading things that don't need it.
Thread Starter
Launching!
Joined: Sep 2008
Posts: 222
Likes: 46
From: Dayton, OH
Thread Starter
Launching!
Joined: Sep 2008
Posts: 222
Likes: 46
From: Dayton, OH
You do not need To port the heads. LS3 castings flow mega air and don’t need ported except in extreme max-effort builds. Your thread topic asks what limits RPM? RPM is limited by airflow and /or a rev-limiter device. That’s it. Get the air in the cylinder, and get it out of the cylinder. 7k rpm isn’t a big deal these days in the pushrod world. Valves have to be controlled with the correct springs...this is a must...and you’ll need a camshaft capable of getting it there. The LS3 intake manifold is very good in raw form, but there are porting and radius rod mods that help it a lot. The intake tract in front of the manifold needs to be as restriction free as possible, and a 102mm throttle body will help also. Nothing wrong with the latest version of YT rockers, just make sure your springs are specced for the addition nose weight from the YT’s. It’s roughly 10 grams...I’ve weighed them.
Are you looking for a power goal, or do you just want to turn rpm regardless?
Are you looking for a power goal, or do you just want to turn rpm regardless?
I was looking for something else and ran across this;
"ULTRALITE
Yella Terra’s exclusive Ultralite rocker arm, shaft and pedestal system offers 50% less nose weight than the factory rocker system, the result being greater RPM potential without compromising strength or durability. The perfect low-maintenance substitute for factory rocker arms which utilise problematic cage-less bearings, solid non-roller tips and heavy steel bodies. Yella Terra Ultralite is ideal for high revving street applications when coupled with factory/lightweight aftermarket springs."
According to Yella Terra their Ultralite rockers have 50% LESS nose weight.
Last edited by SteveJewels; Nov 29, 2020 at 08:38 AM.
@Chev70elle I really appreciate your help Scott. I am very interested and have a lot to learn about LS engines.
I was looking for something else and ran across this;
"ULTRALITE
Yella Terra’s exclusive Ultralite rocker arm, shaft and pedestal system offers 50% less nose weight than the factory rocker system, the result being greater RPM potential without compromising strength or durability. The perfect low-maintenance substitute for factory rocker arms which utilise problematic cage-less bearings, solid non-roller tips and heavy steel bodies. Yella Terra Ultralite is ideal for high revving street applications when coupled with factory/lightweight aftermarket springs."
According to Yella Terra their Ultralite rockers have 50% LESS nose weight.
I was looking for something else and ran across this;
"ULTRALITE
Yella Terra’s exclusive Ultralite rocker arm, shaft and pedestal system offers 50% less nose weight than the factory rocker system, the result being greater RPM potential without compromising strength or durability. The perfect low-maintenance substitute for factory rocker arms which utilise problematic cage-less bearings, solid non-roller tips and heavy steel bodies. Yella Terra Ultralite is ideal for high revving street applications when coupled with factory/lightweight aftermarket springs."
According to Yella Terra their Ultralite rockers have 50% LESS nose weight.
TECH Enthusiast
Joined: May 2008
Posts: 644
Likes: 575
From: Carnation, WA
I think the nose weight difference measured in that way would be *less* with bearings in the stocker. The nose weight of the stocker would go to (say) 35g from 33g, assuming the bearings were only 4g split evenly between the nose and the other end. That's what I was getting at. So assuming those numbers, only 8g difference, not 10g. Agreed the bearings don't affect the nose weight, but they do affect this measurement ... which I also think was cleverly done. :-)
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Verdad Gallardo TECH Fanatic
Joined: Dec 2019
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Seeing as how stock rocker bodies have been 9000 RPM, and most aftermarket rocker systems released in the last 3 years have all used stock rocker bodies, there isn't much reason to upgrade. It just won't be worth the cost.
TECH Addict
Joined: Jul 2013
Posts: 2,189
Likes: 123
From: Portland, Oregon
Pretty sure stock LS3 heads can support stock LS3 displacement to ~8000rpms... what limits the stock engine from spinning that high? The driver. Lol.
Probably need some dual valve springs and better rod bolts to spin to 8K safely. Not sure if the stock intake can support that, though. Might want forged rods/pistons, but I don't know if they are absolutely necessary.
Probably need some dual valve springs and better rod bolts to spin to 8K safely. Not sure if the stock intake can support that, though. Might want forged rods/pistons, but I don't know if they are absolutely necessary.