I setup my tune to limit fueling at 4000... I only rev it that high in 4th gear to help out the trans. I have had it just over 4000 a few times... IMO that's a good place to quit with a stock motor... hopefully I'm not wrong :angel:
What is safe RPM to turn
- Thread starter Vasbinder
- Start date
The factory red-line isn't 4800 I haven't had a factory dash in mine for a long time but 4800? Really?
I do know that I read some where that the factory Allison isn't suppose to be spun 5000 rpm or above or it can grenade. Not taking in to play here the aftermarket items available today that might make that statement obsolete but I do know that the Allison stock fresh has a RPM limitation and I do believe it is 5k.
So how or would GM allow it to spin that close to grenading?
I do know that I read some where that the factory Allison isn't suppose to be spun 5000 rpm or above or it can grenade. Not taking in to play here the aftermarket items available today that might make that statement obsolete but I do know that the Allison stock fresh has a RPM limitation and I do believe it is 5k.
So how or would GM allow it to spin that close to grenading?
Has anyone read it where GM or the engine plant really tells where they test these engines on the long run time dyno tests? They sure abuse the ones that are used for that test mule power line. I've always wondered on max and what time is done for on Duramax after seeing some clip on the GM performance test site with new 454LSX mill.
We have spun many stock turck to 4500 or better and i spin my built motor to 5. With that being said i believe that was a contributing factor to my crank breaking spinning that high. In the end its up to you if you want to take the risk. And yes without the right injectors and turbos they dont make power up there anyway
The biggest problem for damages seem to be push rods that beand when the valve guide clearances tighten up and pinch the valve. Secondly, you don't have enough air to benefit from turning one that hard. Even with bigger turbos it would be hard to benefit from turning over the 4500 range. A 66 mm turbo doesn't benefit from running past the 3600 range.
^^ That's what I am saying. The factory redline is ~4800 RPM. True, it is for grade braking, but it is the redline nonetheless.
I personally disagree with the thought that it is easier on the engine to spin it up via grade braking than under under power. Why? Because the engine is designed to have high pressures on the top of the piston to help slow it down and turn it around. There are much higher pressures when under power than when grade braking. Now too much pressure can cause problems, at any RPM. But I'm talking about reasonable cylinder pressures.
It is all sort of a moot point for a stock engine, as fuel and air run out well below 4800 RPM (I loose a significant amount of airflow by 3400 RPM according to my logs). However, as long as you keep the timing and PW reasonable, I can't imagine damaging the engine from spinning it to 4800 RPM. But if you aren't comfortable doing it... don't do it!
I could be 100% wrong on all these points, though. And thanks to everyone who posted their results above 4000 RPM. Good to know!
I like to think of "safe" as a relative term because all speeds are safe till shit starts breaking lol!!
Maybe I'm just thinking outload, but I've run stock BBC hydraulic valvetrain parts to 6500, with only upgraded springs for the increased cam lift. No issues with that, and that was 1972 technology. The roller cam here would defiantly need better parts than what I was spinning then, but I am just thinking outload.
http://www.youtube.com/watch?v=UMxN3QzLsvs
This was over 4500 rpms, with completly stock heads. This charger makes plenty of power at 4500+ too.:thumb:
This was over 4500 rpms, with completly stock heads. This charger makes plenty of power at 4500+ too.
:thumb:
I like go keep the RPM'S out of the red that's why I need to get the PPE fixed. It's pretty easy to get it in the red when playing. Thanks for all the info.
Does any body know if a update from PPE will fix the red line problem. Maybe Dan will see this and chime in.
