Whats it take to spin 7.5k?
10-20-2016, 06:33 PM
#1
Whats it take to spin 7.5k?
So I m not new to the ls game, I came from the 4th gen world. I ve done h/c before but never really liked how my car preformed and went turbo. Now that I m an adult with a real car, thought I would try it again before I go fi. I know ls1s don't like to go past 6500 rpms on stock internals but I don't know the limits of an ls3. Look to hear from you high reving cammed ls3 guys. Obviously springs, push rods and rocker arms a must
10-21-2016, 12:22 PM
#2
Safety Car
So I m not new to the ls game, I came from the 4th gen world. I ve done h/c before but never really liked how my car preformed and went turbo. Now that I m an adult with a real car, thought I would try it again before I go fi. I know ls1s don't like to go past 6500 rpms on stock internals but I don't know the limits of an ls3. Look to hear from you high reving cammed ls3 guys. Obviously springs, push rods and rocker arms a must
Last edited by irok; 10-21-2016 at 12:24 PM.
10-21-2016, 01:06 PM
#3
Former Vendor
You aren't going to get there with an LS3 in 2 aspects, reliability and cost.
Stock heads won't flow up there
Stock lifters won't survive either
While a hyd cam can live up at that RPM, it won't last long which means you will need to go to solid roller.
You will need an aftermarket shaft rocker system as well as a lot of Ti items. And then when you go FI you will need to change it all again because all of that stuff won't handle the added pressure from FI.
And their is a ton more to discuss when turning that much RPM.
Stock heads won't flow up there
Stock lifters won't survive either
While a hyd cam can live up at that RPM, it won't last long which means you will need to go to solid roller.
You will need an aftermarket shaft rocker system as well as a lot of Ti items. And then when you go FI you will need to change it all again because all of that stuff won't handle the added pressure from FI.
And their is a ton more to discuss when turning that much RPM.
10-21-2016, 02:35 PM
#4
Supporting Vendor
10-21-2016, 04:26 PM
#5
Racer
So... this is really a question of what kinda power and torque your camshaft, heads, and valve-train can pump out at 7500+ rpm. The stock LS3 corvette cam starts to fall over around 6000 rpm and even most aftermarket street/strip cams fall off around 6700. What is the application you need 7500 rpm shift points for?
10-21-2016, 04:34 PM
#6
So... this is really a question of what kinda power and torque your camshaft, heads, and valve-train can pump out at 7500+ rpm. The stock LS3 corvette cam starts to fall over around 6000 rpm and even most aftermarket street/strip cams fall off around 6700. What is the application you need 7500 rpm shift points for?
I don't need it at 7500rpm, was just throwing out number. I m thinking more like running to 7K with a limit at 7200.
10-21-2016, 04:38 PM
#7
You aren't going to get there with an LS3 in 2 aspects, reliability and cost.
Stock heads won't flow up there
Stock lifters won't survive either
While a hyd cam can live up at that RPM, it won't last long which means you will need to go to solid roller.
You will need an aftermarket shaft rocker system as well as a lot of Ti items. And then when you go FI you will need to change it all again because all of that stuff won't handle the added pressure from FI.
And their is a ton more to discuss when turning that much RPM.
Stock heads won't flow up there
Stock lifters won't survive either
While a hyd cam can live up at that RPM, it won't last long which means you will need to go to solid roller.
You will need an aftermarket shaft rocker system as well as a lot of Ti items. And then when you go FI you will need to change it all again because all of that stuff won't handle the added pressure from FI.
And their is a ton more to discuss when turning that much RPM.
10-21-2016, 11:19 PM
#8
Pro
stock bottom end and still stock lifters and I shift at 7200 - 7300 limiter is set at 74 and have bounced off it a few times
car had 16 thousand miles on it when I did cam and heads and now has 35 so it's held up good but realize it could go at any time the way I run it, I do have titanium retainers and hollow stem valves to lighten valve train and running stock rockers with trunion upgrade so its definitely doable
10-22-2016, 01:05 AM
#9
I have an ls6 not an ls3 but I would think if the internals were as good or better than the ls6 7000 shouldn't be a problem
stock bottom end and still stock lifters and I shift at 7200 - 7300 limiter is set at 74 and have bounced off it a few times car had 16 thousand miles on it when I did cam and heads and now has 35 so it's held up good but realize it could go at any time the way I run it, I do have titanium retainers and hollow stem valves to lighten valve train and running stock rockers with trunion upgrade so its definitely doable
stock bottom end and still stock lifters and I shift at 7200 - 7300 limiter is set at 74 and have bounced off it a few times
car had 16 thousand miles on it when I did cam and heads and now has 35 so it's held up good but realize it could go at any time the way I run it, I do have titanium retainers and hollow stem valves to lighten valve train and running stock rockers with trunion upgrade so its definitely doable
10-22-2016, 01:49 AM
#10
Melting Slicks
An ls3 with small intake port and big flow like Trick flow 255 cc heads and a low lash solid roller will do 7.3 no question and make a lot of power can be shifted at 7.5 at the track for best times.
Above heads could be shaved enough to make 14 to 1 with stock pistons on e85 drive it on the street all day with appropriate fluids cooling, engine oil and coolant will have additional cooling needs but hey! no inter cooler or additional weight from boosters tubing clamps complexity.
Then turn around and take 230 lbs off the car for equalizer haha.
Above heads could be shaved enough to make 14 to 1 with stock pistons on e85 drive it on the street all day with appropriate fluids cooling, engine oil and coolant will have additional cooling needs but hey! no inter cooler or additional weight from boosters tubing clamps complexity.
Then turn around and take 230 lbs off the car for equalizer haha.
10-22-2016, 11:51 AM
#11
Pro
Stock rod bolts, the older ls1's had the weaker rod bolts, after reading about several trunnion issues I'll probably pull mine apart this winter to check since they have about 20 thousand miles on them, I don't think you would have any problems shifting at 7000
10-23-2016, 02:55 AM
#12
Burning Brakes
My car is a stock cammed car but I cross the traps at 7100-7300 hitting the limiter some times and its fine. I don't see why you wouldn't be able to shift at 7000 with some good valvetrain
10-27-2016, 10:00 AM
#13
I'm thinking I might just do that. I did some more research and plenty of people spin higher than 7500 but the consensus seems if you're going to go to 7500 you might as well be spinning to 8K. I did come across some cool engines like the destroked ls3 331 hot rod did (spins to 8400) and a few flat plane crank conversions. SAM built an lsx 434 that goes to 10K. Rpm is def. Do able but I'm a turbo guy at heart lol.
06-02-2018, 01:05 AM
#14
so what did you end up doing here? I'm going to be running tfs heads with yt rockers and and wondering how high I'd be able to spin if I added lifters into the mix. 800-1000 more rpm out of the ls3 would be wicked. Just wondering what kind of longevity issues might be there, even if you build properly.
06-02-2018, 01:39 AM
#15
Pro
Cam Motion Low Lash Solid Roller set up can
Provide 8000 RPM Stability, Stock LS3 bottom end
should be able to handle 7500 RPM for 1/4 mile
Shift points, ported oil pump to address cavitation
would help beyound ~7200 RPM along with other
Oiling mods. MMS, TFS,AFR,or MAST Heads, along
With the FAST LS3 with Mid-Length Runners.
Wouldn't take too big of a cam to get a 7000 RPM
HP Peak that carries to ~7500 RPM.
Something Like 241*/249* (hydraulic equivalent
Roughly 235*/243* adjusted for Lash) similar to
the Vengeance "Kaotic" with another .050" lift.
Roller Rockers, Good Lifters, Springs, and Push Rods.
It has been done on LS1 Tech for a while now.
At least 12-18 months.
Provide 8000 RPM Stability, Stock LS3 bottom end
should be able to handle 7500 RPM for 1/4 mile
Shift points, ported oil pump to address cavitation
would help beyound ~7200 RPM along with other
Oiling mods. MMS, TFS,AFR,or MAST Heads, along
With the FAST LS3 with Mid-Length Runners.
Wouldn't take too big of a cam to get a 7000 RPM
HP Peak that carries to ~7500 RPM.
Something Like 241*/249* (hydraulic equivalent
Roughly 235*/243* adjusted for Lash) similar to
the Vengeance "Kaotic" with another .050" lift.
Roller Rockers, Good Lifters, Springs, and Push Rods.
It has been done on LS1 Tech for a while now.
At least 12-18 months.
06-02-2018, 01:51 AM
#16
Melting Slicks
Forget about the valvetrain for a minute. The real issue is oil system, oil control. A stock bearing clearance isn't going to be adequate for extremely high RPM. Even showing 100psi of oil pressure the farthest bearings can starve if clearance is tight enough.
And new engines are all about tight clearance.
When you want a very high RPM you rebuild the engine with larger than factory bearing clearance, and use thicker "racing" weight oil. Typically 50 or 60W. Since the engine is used for racing purposes you ensure complete pre-warming before an event and it never cools off during that event, thus single grade oil is ideal for that competitive event.
Somewhere between 1-race day 1-grade racing 50W oils and daily driver capable 0W-20 oils is everything between a high RPM race car and a cold-start friendly minimal cold-wear maximal warm-up daily driver. And its in the 0.002" of difference at the bearing that determines this.
And new engines are all about tight clearance.
When you want a very high RPM you rebuild the engine with larger than factory bearing clearance, and use thicker "racing" weight oil. Typically 50 or 60W. Since the engine is used for racing purposes you ensure complete pre-warming before an event and it never cools off during that event, thus single grade oil is ideal for that competitive event.
Somewhere between 1-race day 1-grade racing 50W oils and daily driver capable 0W-20 oils is everything between a high RPM race car and a cold-start friendly minimal cold-wear maximal warm-up daily driver. And its in the 0.002" of difference at the bearing that determines this.
06-02-2018, 11:59 AM
#17
Forget about the valvetrain for a minute. The real issue is oil system, oil control. A stock bearing clearance isn't going to be adequate for extremely high RPM. Even showing 100psi of oil pressure the farthest bearings can starve if clearance is tight enough.
And new engines are all about tight clearance.
When you want a very high RPM you rebuild the engine with larger than factory bearing clearance, and use thicker "racing" weight oil. Typically 50 or 60W. Since the engine is used for racing purposes you ensure complete pre-warming before an event and it never cools off during that event, thus single grade oil is ideal for that competitive event.
Somewhere between 1-race day 1-grade racing 50W oils and daily driver capable 0W-20 oils is everything between a high RPM race car and a cold-start friendly minimal cold-wear maximal warm-up daily driver. And its in the 0.002" of difference at the bearing that determines this.
And new engines are all about tight clearance.
When you want a very high RPM you rebuild the engine with larger than factory bearing clearance, and use thicker "racing" weight oil. Typically 50 or 60W. Since the engine is used for racing purposes you ensure complete pre-warming before an event and it never cools off during that event, thus single grade oil is ideal for that competitive event.
Somewhere between 1-race day 1-grade racing 50W oils and daily driver capable 0W-20 oils is everything between a high RPM race car and a cold-start friendly minimal cold-wear maximal warm-up daily driver. And its in the 0.002" of difference at the bearing that determines this.
so where do you feel oil becomes a limiting factor if the valve train is solid?
06-02-2018, 01:04 PM
#18
Melting Slicks
Last time I checked real race cars using high tech oil system containment strategy go by flow rate through the engine, not pressure. They are measuring the amount of oil that comes out of the engine per unit time, at some RPM. Then adjusting that up or down, regardless of what pressure says.
Without being able to measure flow rate coming out, all you have is the pressure number of what is going in. Auto manufacturers have been making engines tighter and tighter since the 60's, its gotten so tight now that they are using 0W oils for cold start flow. And still able to achieve a reasonable RPM range. But if everybody starts out with the same exact engine- only the person who modifies theirs to go a little harder, a little higher, can win the race. So what it really comes down to is how serious is the race. If you are not racing seriously for $$ then you don't probably need an additional 1000-2000 rpm of headroom for power. The stress on the engine past 6k becomes ridiculous quickly, and often there are 'easier' less stressful ways to increase power around 6k (more boost pressure is often 'easier' than another 1k rpm) that does not infringe on oil system capability.
06-02-2018, 01:23 PM
#19
Did you mean oil pressure?
Last time I checked real race cars using high tech oil system containment strategy go by flow rate through the engine, not pressure. They are measuring the amount of oil that comes out of the engine per unit time, at some RPM. Then adjusting that up or down, regardless of what pressure says.
Without being able to measure flow rate coming out, all you have is the pressure number of what is going in. Auto manufacturers have been making engines tighter and tighter since the 60's, its gotten so tight now that they are using 0W oils for cold start flow. And still able to achieve a reasonable RPM range. But if everybody starts out with the same exact engine- only the person who modifies theirs to go a little harder, a little higher, can win the race. So what it really comes down to is how serious is the race. If you are not racing seriously for $$ then you don't probably need an additional 1000-2000 rpm of headroom for power. The stress on the engine past 6k becomes ridiculous quickly, and often there are 'easier' less stressful ways to increase power around 6k (more boost pressure is often 'easier' than another 1k rpm) that does not infringe on oil system capability.
Last time I checked real race cars using high tech oil system containment strategy go by flow rate through the engine, not pressure. They are measuring the amount of oil that comes out of the engine per unit time, at some RPM. Then adjusting that up or down, regardless of what pressure says.
Without being able to measure flow rate coming out, all you have is the pressure number of what is going in. Auto manufacturers have been making engines tighter and tighter since the 60's, its gotten so tight now that they are using 0W oils for cold start flow. And still able to achieve a reasonable RPM range. But if everybody starts out with the same exact engine- only the person who modifies theirs to go a little harder, a little higher, can win the race. So what it really comes down to is how serious is the race. If you are not racing seriously for $$ then you don't probably need an additional 1000-2000 rpm of headroom for power. The stress on the engine past 6k becomes ridiculous quickly, and often there are 'easier' less stressful ways to increase power around 6k (more boost pressure is often 'easier' than another 1k rpm) that does not infringe on oil system capability.
All I'm looking for is what rpm is "safe" to spin to, before you reach that point? I don't want to spin to 8000, or even 7500 really. I just want to know where I should set the limit if I've got a very solid valve train, if you feel that oiling/oil pressure/volume etc. becomes the issue.
Seems like the answer is likely 7200-7300rpm
06-02-2018, 03:03 PM
#20
Melting Slicks
Two ways to predict failure
1.
Problem: An engineer with the model can predict the odds of failure. This is undoubtedly done by the OEM engineers who originally design it etc...
solution: You could make your own models to predict failure for old/new parts/combinations
2.
Problem: Through experimentation results, i.e. run a population of engines 10x have a 7200rpm redline, 10x have 7300, 10x have 7400, etc... with identical oil setups and then experiment and tweak to find the optimal, longest lasting champion combination. The next step is to copy it down, program it to a computer which can automatically machine and produce identical copies of this award winning engine with as little human/computer error introduced as possible technologically at the time. The OEM are largest and most capable, i.e. the closest thing to this.
1.
Problem: An engineer with the model can predict the odds of failure. This is undoubtedly done by the OEM engineers who originally design it etc...
solution: You could make your own models to predict failure for old/new parts/combinations
2.
Problem: Through experimentation results, i.e. run a population of engines 10x have a 7200rpm redline, 10x have 7300, 10x have 7400, etc... with identical oil setups and then experiment and tweak to find the optimal, longest lasting champion combination. The next step is to copy it down, program it to a computer which can automatically machine and produce identical copies of this award winning engine with as little human/computer error introduced as possible technologically at the time. The OEM are largest and most capable, i.e. the closest thing to this.