What is a safe RPM to turn before something lets go. When pulling out a stuck friend I left truck in second and nailed it. Looked down and truck was at 4500 rpm's. Have a PPE on level 3. I don't need a rod hanging out the block.
What is safe RPM to turn
- Thread starter Vasbinder
- Start date
i would say you have a good chance of having a few bent pushrods. at least thats what happened to me
Doesn't the stock engine allow you to turn 4500 RPM (while grade braking)? So how would this bend pushrods?
I could see floating the valves a little, but that is just a loss of power, not permanent damage.
But I could be wrong. Subscribed!
I could see floating the valves a little, but that is just a loss of power, not permanent damage.
But I could be wrong. Subscribed!
my truck will rev to 5k just sitting there. i've never tested it with a load on the engine, but i still dont think its a good thing. I would like to know this also! It can't be good on stock valvetrain......but it kinda sounds cool and no other dmaxs around can do it, so i get talked into showing it out after a couple of cold drinks
Anyone with a tune can do it if the tune is written so it can rev that high.my truck will rev to 5k just sitting there. i've never tested it with a load on the engine, but i still dont think its a good thing. I would like to know this also! It can't be good on stock valvetrain......but it kinda sounds cool and no other dmaxs around can do it, so i get talked into showing it out after a couple of cold drinks
im one of the only ones running EFI around....I guess my question is, is this ok to do or should i forget about it? haha
What do you risk breaking? Especially just revving in neutral, I can't see the difference between that and grade braking.
Do you put your truck in neutral when it grade brakes into redline?!?
FWIW my truck turns right around 4500 in 3rd before i shift to 4th pulling. It has completely stock heads at the moment, and has for 6 or more pulls on it after i had to put them on.
First of all, I have never seen my truck grade brake much over 4k RPM. Second, the redline on my truck is at 4800 RPM, which is at least 200 less than 5k+ RPM. Also, There is a difference between the transmission spinning the engine to whatever RPM it goes to and the engine doing it itself. You risk floating valves and bending push rods or worse case spinning a bearing or throwing a rod (unlikely, but much more likely at higher RPM than at lower). My question is why would you want to rev it that high in the first place? Are you really going to tell me that that RPM is just as safe as 3k? Like I said, you do what you want, but I won't spin my stock engine at that many RPM. I don't see any reason to go over 4k. Much over that is just asking for trouble in my opinion.
I agree, I don't see the need to push a stock engine over ~3600 RPM, as there isn't enough airflow, and the pulsewidth is just too long at those RPMs. At least that's the case on my old LB7...
I still can't see how it would bend a push rod as long as you kept it below 4800 (the factory redline). I can see floating the valves, under power or not, but so long as they don't contact the pistons you're fine. I haven't heard of many (any?) cases where 4800 RPM caused the valves to hit the pistons. I'll bet the valves are floating a little under grade braking, completely stock. Won't hurt much, if anything, really.
IMO the likelihood of spinning a bearing or throwing a rod are identical weather under power or grade braking at high RPM (well, under reasonable amounts of power). There are higher loads on components at high RPM, but those loads pale in comparison to a tuned engine at WOT.
But like you said, do what you want with your engine. I only turn 3600 RPM on mine, because I run out of airflow. If I twin turbo it and get bigger injectors, I'll probably crank it up to 4800 just to see what happens. I'll bet nothing terrible happens, but I'll have to wait and see. And it it blows, time for some additional upgrades
If anyone has taken a stock valvetrain above 4k under WOT, I'd love to hear about the results, good or bad!
I still can't see how it would bend a push rod as long as you kept it below 4800 (the factory redline). I can see floating the valves, under power or not, but so long as they don't contact the pistons you're fine. I haven't heard of many (any?) cases where 4800 RPM caused the valves to hit the pistons. I'll bet the valves are floating a little under grade braking, completely stock. Won't hurt much, if anything, really.
IMO the likelihood of spinning a bearing or throwing a rod are identical weather under power or grade braking at high RPM (well, under reasonable amounts of power). There are higher loads on components at high RPM, but those loads pale in comparison to a tuned engine at WOT.
But like you said, do what you want with your engine. I only turn 3600 RPM on mine, because I run out of airflow. If I twin turbo it and get bigger injectors, I'll probably crank it up to 4800 just to see what happens. I'll bet nothing terrible happens, but I'll have to wait and see. And it it blows, time for some additional upgrades
If anyone has taken a stock valvetrain above 4k under WOT, I'd love to hear about the results, good or bad!
I have Socal hardware and seen well above 4500 many times and still don't like it
I have a mild cam and big turbos and don't produce good hp up there.... So what's the point?
I seen logs on shifts at 5400rpm now that gets the mind going
I have a mild cam and big turbos and don't produce good hp up there.... So what's the point?
I seen logs on shifts at 5400rpm now that gets the mind going
I agree, I don't see the need to push a stock engine over ~3600 RPM, as there isn't enough airflow, and the pulsewidth is just too long at those RPMs. At least that's the case on my old LB7...
I still can't see how it would bend a push rod as long as you kept it below 4800 (the factory redline). I can see floating the valves, under power or not, but so long as they don't contact the pistons you're fine. I haven't heard of many (any?) cases where 4800 RPM caused the valves to hit the pistons. I'll bet the valves are floating a little under grade braking, completely stock. Won't hurt much, if anything, really.
IMO the likelihood of spinning a bearing or throwing a rod are identical weather under power or grade braking at high RPM (well, under reasonable amounts of power). There are higher loads on components at high RPM, but those loads pale in comparison to a tuned engine at WOT.
But like you said, do what you want with your engine. I only turn 3600 RPM on mine, because I run out of airflow. If I twin turbo it and get bigger injectors, I'll probably crank it up to 4800 just to see what happens. I'll bet nothing terrible happens, but I'll have to wait and see. And it it blows, time for some additional upgrades
If anyone has taken a stock valvetrain above 4k under WOT, I'd love to hear about the results, good or bad!
Since when is factory redline 4800rpm... guess I got a gasser dash that redlines at 3250 like every other dmax. grade brake is 4800rpm, ive spun 4500 a few times under grade brake, but slowing down at high rpm is way easier on a motor than the same rpm under a load..
my race tcm tune is set to shift at 3700 but it reaches just shy of 4k before it shifts.
we spin stock internal trucks to 4500ish when sled pulling without a failure in two years doing so. not saying it's great to do or safe but we know the risk and have parts ready to go in when/if shit hits the fan. Other then during competition though, we don't run them that high.