like to know the answer as well. I read alot about this "high rpms", but, whats considered high?

When my turbo went, i was WOT, getn on a freeway. I swear SOMETHING has happened to the motor but has yet to show its face

 

That is very pricey and probably not worth it unless you were going for a very reliable high horsepower build.

Timmyboy76, I to have read about the "high" rpms but there's never any numbers to shoe what the mean by high. I've always assumed that high rpms meant past redline but we all know what happens when you assume lol

 

I really don't know what number/ rpm would start to cause and issue but these are diesel engines and diesels in general are low rpm's and high torque. I think anything over 3200rpm's is high but I am an old guy. You shouldn't be winding these motors up, it's a diesel not a small block gasser. If you can't make the power in the low end or mid range hang it up. Sorry just the old guy in me talking/

 

i'm more inclined to twist this motor when towing into the 2500-2700 rpm range. Seems to be a "sweetspot" for my rig. Alll stock, nothing spectacular, just want to get where im going.

I'm not sure my truck can even GET TO 3k rpms, unless it used to when prior to turbo popping.

 

Those rockers are made by Harland Sharp.. Unless you go out and get a custom solid roller cam, there isn't really much reason in buying those adjustable roller rocker arms. With our hydraulic cams, there is not much reason in having an adjustable lash rocker arm unless it's purely for the stronger design.. The stock rockers shouldn't have any problems until you start spinning a little over 4000 rpm on a consistent basis. I've spun my 390k mile OBS to 4000 RPM A LOT and it has survived with it's 100% stock valve train. I did change to chromoly pushrods one night b/c I thought I bent one, but I didn't. The rockers should be ok as long as there is no valve-to-piston contact. Valve float at these RPMs and boost levels can be a real problem, so this is where most bent pushrods and broken rockers at high RPM will likely come from.

You're right, in general diesels are a low RPM engine due to the weight of the parts and the speed at which the injection systems are able to reliably inject fuel into the cylinder.

I wouldn't say, however, that "you shouldn't be winding these motors up". If you could get the injection system to inject enough fuel into the cylinder in a short enough period of time to run 4000-4500 RPM on the street, that would make all of our current proven power setups capable of making even more usable power. It would also allow some of us to run an even larger turbo for a given injector size b/c we'll be able to pull more RPMs to get it moving. That potentially means even more power from the injectors we currently have available. These larger turbos should be more drivable as well. Think of the power curves we normally see right now. They almost all drop power dramatically around 3000-3200 RPM.

My own truck comes on the turbo at 2000 RPM. At 2200 RPM it's over 510hp. It peaks at 518hp around 2800 RPM. The power band from 2200-3500 RPM stays between 510-518hp.. So I have about 1300 RPM where I can use all this power before having to run the next gear. What happens every time you go to the next gear? Essentially you accelerate slower, less power is being applied to the pavement. Extend that power band out to 4000 or even 4500 RPM.. Even if you could just hold between 500-518hp from 2200-4500 RPM, that would make for a much more useful power band and would be a whole lot more fun to drive. Because one of the biggest downsides of a diesel engine is running out of RPM and gear so quickly.. IMO of course...

 

Nice write up Travis. What are you running for injectors and Turbo? Stock IDM? Stock HPOP? I like to ask questions, its just for future working on maybe an older truck I mit pick up, Thanks

Chet

 

Here's the list of mods on my OBS..

160/100 Rosewood injectors
TW live tuning
DI intercooler
modded 17* HPOP (dropping to 2100psi, needs a T500 or dual pumps)
S466/83/.90 turbo
HPX
water/methanol injection w/ dual nozzles (spraying 55% VP racing M1 methanol)
Dieselsite electric fuel system w/ regulated return and a Walbro pump
CCV mod

I'm sure I'm missing some stuff, but that should be most of it. The setup made 460hp on fuel only and 518hp with methanol injection. There's more there with an HPOP swap, but I'm still running stock head bolts and stock valve springs, so I'm waiting to push it any harder until I get an engine built for it.

 

pushing those 160/100's pretty far! im glad to see that, how much more do you think you can get out of it with a better hpop setup?

 

I think there may be another 10, maybe 15hp available if I'm lucky. I believe there may also be a boost leak somewhere b/c on fuel only it only builds ~33-34psi of boost and on methanol it makes 38psi. I should be able to drive this charger, despite the large turbine, to 35+psi with these 160s on fuel only IMO. I might fix the uppipes and see how much more I can pull out of it before throwing the built engine in it. Not sure yet.

 

Travis for sharing your first hand experience with us and 518hp is impressive! And thank you for pointing out that the rockers are made by Harland Sharp. Now I just need to make a mental note.....wait a minute I forgot??

Now as far as running roller rocker arms with adjustable lock nuts I use them all the time on gassers with hydraulic cams. And this summer I was working a boat with 502's roller cam & rockers in it and the guy was having problems with valve lash and he was adjusting them by the book and it just wasn't right. Mind you this boat was rode hard and hung up wet, this guy over revs them often and the engines are due for a overhaul. But I think he had a couple bad lifter bores or couple of lifters not pumping up all the way. But I was able quiet them up by adjusting the roller rocker with the motor running. Thanks to the adjustable lock nuts. So I was able to buy the guy some time. Now from what you have said and others have done the stock rocker arm might hold up ok but there is many advantages to roller rocker arms. Mind you I have put them on almost all gassers I work on cars and boats and have never payed more than $300 that is why I just think Harland Sharp prices are insane. At $300 it is money well spent.

Now I see you point about wanting to get into the 4000rpm range for what you do with your truck but I myself use mine mostly as tow vehicle and would never want to go that high. But I think you are right in most cases it's valve float & high boost is the main issue on these 7.3's. But I would aso think once you get to 3500-4000rpm you run a higher chance of throwing a rod or snapping a crank. So not for me but you go for it!
Been there done that back in the day with a BBC 454 and 460 Mustang too many rpms and the bottom end went "BOOM" and sometimes valve into a piston action.

 

There's definitely some engine strengthening that's needed before you should be pushing into the 4000+ RPM range. Stock rods actually seem to hold together better when you slide the power band up into the higher RPM range. Especially around that 1200tq number.

Myself, for a tow pig, it would still be beneficial to be able to run it up to 4000 rpm if the engine itself was up to the task.

 

did that today with an engine on an engine dyno, somebody nicked a valve stem while grinding the valves and it stuck the intake valve into the piston when it broke... shouldve taken a pic. after we disassembled it

 

The engine that made me start this thread has 360k on it and is totally stock.

Being a northern truck, I could imagine it had a lot of idle time. I hope he tears it down... didnt get to talk to him today.

 

I hope he pulls the heads off and at least pulls the valves out of that cylinder and looks at the lifters from that cylinder. It wouldn't take a ton of time to do check that stuff out if the engine is already removed. Grab the impact and get after it.

 

Building gasser motors at a speed shop the main cause of push rod failure I saw was from lifter issues or rocker studs pulling allowing the push rods to fall aside and get bent.

Travis, by definition in engines, Power Band is the range between peak torque and peak horsepower. I see you HP numbers (is 518 @ 2800 your max HP), so to determine your power band we would need to know your max torque rpm. These rpm numbers would establish your power band. Max torque RPM to Max HP RPM.