The highest RPM safe to run for long distanced??? (too low of gear's!!)
#1
Registered User
Thread Starter
Join Date: Nov 2005
Location: IN
Posts: 269
Likes: 0
Received 0 Likes
on
0 Posts
The highest RPM safe to run for long distanced??? (too low of gear's!!)
I just lowered my truck back down to 35in tires, it did have 40in, (more like 38's). With the biggier tires my stock gearing just wasn't doing it, so i putt 4.56's in it. I still felt it was a little off, like it sould be lower. But i knew some day i would prob be back down to 35's or so. Yesterday i got the truck done and on the road with the 35's. Its, well, differnt to say the least. My speedo is still of, so i don't really know on how fast i was going, But i was running with traffic on the interstate (with speed limit 70) and my RPM's were around the 2500 mark.. With having stacks, it just sounded like the truck was screaming!! So, besides the poor fuel milage, can this take its toll on a motor after many miles of running that high of RPM's?? My boost read about 16-20 and pyro around 700* just with cruse set. I did do a ratio calculator on Rany's ring web site, before i did this, and it said it would be a few RPM's off than a truck with 4.10's and 235's. Dose all of this sound right?? Help me out fellas!!-Chris
#2
Registered User
Join Date: Aug 2005
Location: Airdrie, Alberta
Posts: 7,780
Likes: 0
Received 0 Likes
on
0 Posts
Not gonna hurt the engine. Gen sets and pumps and other industrial apps, that use the same long block, run for hours and hours at sustained high rpms. 2500 really isn't all that high, but it does sound like its screaming.
#4
Registered User
Join Date: Oct 2007
Location: Florida
Posts: 507
Likes: 0
Received 0 Likes
on
0 Posts
stock gov. springs = 2700 rpm max unless you have the fuel to make it go a big higher like i did.
3gsk= 3000 rpm because of valve float
id change those gears in a hurry . id hat 2500 rpm @ 70 mph
3gsk= 3000 rpm because of valve float
id change those gears in a hurry . id hat 2500 rpm @ 70 mph
#5
Registered User
Thread Starter
Join Date: Nov 2005
Location: IN
Posts: 269
Likes: 0
Received 0 Likes
on
0 Posts
It has a 4k GSK. so i can rev past 2500 if i want. But don't want to hold it that high for very long. I guess the way i have to look at it is, its not made to run 100mph. Oh and forgot to say, the head has been pulled before, and has had EEP valves and valve springs installed along with ported and polished. and studed. So i think they said my valves could handle the higher RPM. I was just concerned about the bottom end.-Chris
#6
I would not hesitate to run mine on the governor if I needed to I've done that before on class 8 semi's heck we used to gear them to run on the governor, manys the big cam 400 or cat that redline at 2100 rpm & turned 1900 at 70mph.
#7
i would agree with the others. i have worked on cummins for a wile now. i was in the air force and never had a problem with one running at to high of an RPM. even our light tug trucks (aka bobtails) rated to 65k tow and run them at the governor.
Trending Topics
#8
With proper valve adjustment and good valve springs you are safe up to around 3,200 rpm on the B series. They will run all day long at 3,000, and can handle short full load rpm up closer to 4,000 rpm.
Never run them without a load on the engine over 1,500 rpm, as that puts too much harmonic distortion on the crankshaft and will lead to lower end failure.
The 98 is probably getting a bit weak in the valve spring department by now, so I would keep the maximum rpm in the 3,000 range.
Never run them without a load on the engine over 1,500 rpm, as that puts too much harmonic distortion on the crankshaft and will lead to lower end failure.
The 98 is probably getting a bit weak in the valve spring department by now, so I would keep the maximum rpm in the 3,000 range.
Thread
Thread Starter
Forum
Replies
Last Post
1985cucv
3rd Gen High Performance and Accessories (5.9L Only)
17
04-28-2009 04:59 AM
Moobesor
3rd Gen High Performance and Accessories (5.9L Only)
4
02-23-2008 09:57 AM
cheff
3rd Gen Engine and Drivetrain -> 2003-2007
9
01-23-2006 09:44 AM
Gear Poet
General Diesel Discussion
26
05-13-2005 11:56 AM
fishin fever
Towing and Hauling / RV
7
02-22-2004 08:32 PM