How much RPM can a stock LB7 handle safely? Stock valve springs, stock cam, stock everything except the tune. Just curious, I certainly don't plan on approaching the limit unneccessarily 
How high can you safely spin a stock LB7
- Thread starter GSXRTURBO1
- Start date
I seen 4200 every day probably for a year, with a pushed injector cup. Never had problems. Hit 5k once and a valve dropped. Plus there's no need to rev that high with a stock turbo or cam probably.
Thanks everyone. :thumb:
I definitely agree there's no reason/advantage to spin it that high with stock components, but I was curious as to how high you could safely go, as well as what the weak points are once you start to exceed 3400 RPM and higher.
i.e. at what RPM does a stock valve/valve spring come in danger of smacking a piston?
How much RPM before you risk bending a pushrod?
How much RPM before you risk throwing a belt or damaging accessories (water pump, power steering, alternator, etc.)
How much RPM before you risk damaging the crankshaft?
Also, I assume these RPM limits would be when the engine is under load, not when it's freewheeling or downshifting, etc.
That said, what about RPM limits when freewheeling or downshifting?
I definitely agree there's no reason/advantage to spin it that high with stock components, but I was curious as to how high you could safely go, as well as what the weak points are once you start to exceed 3400 RPM and higher.
i.e. at what RPM does a stock valve/valve spring come in danger of smacking a piston?
How much RPM before you risk bending a pushrod?
How much RPM before you risk throwing a belt or damaging accessories (water pump, power steering, alternator, etc.)
How much RPM before you risk damaging the crankshaft?
Also, I assume these RPM limits would be when the engine is under load, not when it's freewheeling or downshifting, etc.
That said, what about RPM limits when freewheeling or downshifting?
safely, 3250 rpm. there is a reason for a factory rev limiter.
if you want to push it and cross your fingers your valve springs still hold enough seat pressure to keep the valves from floating, you can go as high as these guys are stating but there is no need to go that high unless your sled pulling and trying to gain ground speed. your going to run into water pump issues above 4k if its still stock as well.
if you want to push it and cross your fingers your valve springs still hold enough seat pressure to keep the valves from floating, you can go as high as these guys are stating but there is no need to go that high unless your sled pulling and trying to gain ground speed. your going to run into water pump issues above 4k if its still stock as well.
But won't the grade braking system let it rev higher than the "rev limiter"?
Which isn't really where the limiter is, its just the end of the fuel table. IIRC the limiter is still at 4500.
there is a big difference between an engine under a major load reving to 4k (like WOT) compared to a motor reving to 4k due to the momentum of an object behind it pushing the drivetrain to spin the motor up to those rpm's. you have hardly any fuel in the combustion chamber igniting at those rpm keeping cyl pressures lower than it would be under WOT at those same RPM's.
He asked whats "safe". safe is what the factory gave us, beyond that anything can happen. i can say that ive not seen hardly any issues with people spinning them to 3600-3700rpm. to me, that doesnt deem it safe though, just not as likely to hurt something as say spinning it to 4k and up where valve float can easily happen on high mileage motors or spin the impeller off the shaft of the water pump.
Anything after 4000 rpm is pushing it IMO, thats where valves can start to float. I ran my stock motor to 4400 a couple times but most of the time it was only for a few seconds. Most don't have a need to go that high in the RPM unless they are making some serious power or have a monstrous turbo.
I might know the guy that owns that truck now. Haha still running strong!!! I'd say 4000 is plenty for a mostly street truck.
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i was always tought to never spin up with out being under load, but then i have never got into the pulling techniques either so i just sit here and eat popcorn :thumb:
I shift mine (lly but essentially the same parts) at 38-3900 in the low gears because it wraps up so fast. I shift from 4th and 5th at about 3500. Limiter in case I miss one is @ 4k.
My first lb7 saw 4k a lot after the overhaul. She's still kicking for the new owners.
My first lb7 saw 4k a lot after the overhaul. She's still kicking for the new owners.
What about burnouts? That's not loadless but way less than having traction. And they are usually revved up pretty high. However I agree a free rev is worse